Particle Imaging Velocimetry (PIV) is emerging as a powerful measurement technique which can be used as an alternative or complementary approach to Laser Doppler Velocimetry (LDV) in a wide range of research applications. The instantaneous planar velocity measurements obtained with PIV make it an attractive technique for use in the study of the complex flow fields encountered in turbomachinery. The data acquired offer several advantages over traditional LDV data: higher accuracy; multiple measurement points and the ability to study both transient and steady state flow phenomena. Many of the same issues encountered in the application of LDV techniques to rotating machinery apply in the application of PIV. Techniques for optical access, light sheet delivery and particulate seeding are discussed. Preliminary results form the successful application of the PIV technique to a transonic axial compressor are presented.

Conventional laser Doppler velocimeters, based on the Doppler difference technique are capable of characterizing 3D flow fields. However, when working with limited optical access, there is an increase in the uncertainties in the measurement of the velocity component of the flow directed along the axis of the instrument. In this paper schemes incorporating interferometric and intensity based techniques are proposed to measure the on-axis velocity component over a wide range of velocities, operating within the constraints imposed by the limited optical access available in turbomachinery applications.

The application of a laser Doppler velocimeter to size measurements of non-spherical particles is discussed in terms of the light scattering properties of spherical particles. The necessary modifications to the probe volume shape and the receiver optics to enable reliable intensity measurements are described. Various approximations must be made to allow size measurements, and the particles should not be too irregular in shape. An exact knowledge of the refractive index of the material to be measured is not necessary, since the technique is sensitive to diffracted light. The development of a rapid and reliable calibration method relying on a combination of Mie-Lorenz and Fraunhofer diffraction theory is described. Finally, some experimental data obtained from cornstarch is compared with measurements of the same material taken from an electron micrograph. These data were in good agreement.

Characteristics of turbulent structure of the corner region affected by channel meandering are investigated using flow visualization and a laser-Doppler velocimetry measurements. DPTV is a visualization technique, which is combined an integrated dye injection method with PTV, and visualize a dye streak pattern of coherent structure and a particle path line simultaneously. According as the channel meandering. Plandtl's first kind of secondary flow develops opposing to Plandtl's second kind of secondary flow in the corner region of the straight portion of the experimental open channel. Following the development of the secondary flow, the coherent structure with large-scale in streamwise and transverse direction is generated near the side wall of which the geometric configuration changes from convex to concave.Large-scale coherent structure near the side wall plays an important roles to increase turbulent intensities and generate large-scale shear structure.

Droplet separators or demisters are extensively used in the chemical industry. The effectiveness of many demisters is decisively affected by droplet sizes. As the misty gas passes through the demister, the liquid droplets impinge on the walls and form a liquid film. A part of this film can be re-entrained by the gas flow in the form of larger droplets. These droplets can escape the demister, affecting its efficiency. The measurement of drop size distributions inside the zigzag passages of the demister can provide useful information about the complex flow phenomena occurring within the demister. In the present work, a wave plate demister of the industrial dimensional specifications has been chosen to investigate the drop size distributions at various flow conditions. The laser diffraction technique has been employed for this purpose. This paper describes the suitability of the technique and presents some laser results to describe the effect of changing flow conditions inside and outside the demister.

Uniform flat field detection of reflected light form opaque aerosol particles can be utilized to determine the material densities of an aerosol spray process and predict material distributions and physical properties of the applied substances. Design of an appropriate lighting system for this type of process monitoring involves consideration of numerous optical and dimensional properties affecting the delivery, scattering, collection, and detection of light. A novel design and analysis technique for this type of optical system is presented.

We present a technique for the measurement of the 2D distribution of the line-average void fraction in a transparent, gas-liquid flow, based on the attenuation of visible laser light by the gas bubbles in the flow. The technique is demonstrated in a test chamber of rectangular cross section. Bubbles are generated by flowing air through twenty holes in the side of a tube at the bottom of the chamber. The collimated beam of an Ar-ion laser traverses the test chamber through front and back Lexan walls, is refocused onto a pinhole and imaged with a CCD camera. Mie scattering by the air bubbles causes a spatial modulation of the laser beam, with the distribution of the logarithm of the light intensity linearly proportional to the distribution of the line average of the interfacial area density. The images are normalized against background non- uniformities and the interfacial area density calculated from the 2D transmittance distribution. The bubble diameter is estimated from the contours of the interfacial area density field and the line-average void fraction is calculated is estimated from the contours of the interfacial area density field and the line-average void fraction is calculated from the product of the interfacial area and bubble diameter fields. The results compare very favorably with measurements of volume-average void fraction based on the swell of the water level consequent to the air injection.

Measurement of drop size distributions in annular two phase flow is required in many parts of industry. In the oil industry this information is needed as the drop sizes in the flow affect heat and mass transfer, pressure drops and also processes like erosion and corrosion. Laser techniques are well suited for this kind of study. In the present work, drop size distributions have been measured in a 38 mm diameter tube in vertical and horizontal positions. Phase Doppler and laser diffraction techniques have been employed for this purpose. Data has been collected for various flow conditions and has been compared with that previously obtained for 32 mm and 20 mm diameter tubes. The effect of pipe orientation on drop sizes has also been analyzed and some typical results have been produced.

A fluorescence sensor system is proposed that integrates emission and detection methods as well as optical and electronic components in a thin film geometry. Predicted properties of this sensor include: increased sensitivity, shielding form unwanted radiation, wavelength filtering, potential operation at high temperatures, and miniaturization. The sensor can be tuned to measure a wide variety of species by varying its thin film corrugation periodicity, in particular, the sensor can be used to detect NO_x.

A diode-laser sensor system has been applied to measure the concentrations of NO, N₂O, CO, and CO₂ in combustion gases using absorption spectroscopy and fast extraction- sampling techniques. Measured survey spectra of the NO 3v band and H₂O lines from the v₂ + v₃ band in the spectral region from 5556 cm^-1 to 5572 cm^-1 were recorded and compared to calculated spectra to select optimum transitions for NO detection. Similarly, measured survey spectra of the N₂O 3v₃ band from 6535 cm^-1 to 6600 cm^-1 were used to identify optimum transitions for N₂O detection. High- resolution NO absorption measurements were recorded in a fast-flow multipass cell containing probe-sampled combustion gases to determine NO concentrations in a laminar, premixed CH₄/air flame, seeded with NH₃. For fuel-lean conditions, the measured No mole fractions corresponded to 68 percent of the injected NH₃. For fuel-rich conditions, the fraction of NH₃ converted to NO decreased with increasing equivalence ratio. In additional experiments, CO and CO₂ absorption measurements were used to determine species concentrations above a laminar, premixed CH₄/air flame. Good agrement was found between measured CO and CO₂ concentrations and calculated chemical equilibrium values.

Variable-density flows create time- and space-varying aberrations in optical wavefronts passing through them. Such aberrations significantly degrade the performance of instruments using this optical 'information'. Since fluid turbulence causes the distortions,they also contain information about the flow that created them. A high speed, optical wavefront sensor would thus be useful both as a means of cuing adaptive-optics systems and for non- intrusive, turbulent flow diagnostics. This paper presents the first effort to develop a high speed, 2D wavefront sensor based on the theory for the 1D, small-aperture beam technique (SABT). The new sensor uses the SABT for measurements in the streamwise direction and scanned beams for cross-stream wavefront measurements. Results of a breadboard implementation of the cross-stream component are presented followed by preliminary result for the full, 2D, SABT-derivative sensor measurements of a low-speed, heated mixing layer.

A three-by-three square array of submerged, elliptic, impinging jets in water was used to study the heat transfer distribution in the cooling process of a constant heat flux surface. Tow jet aspect ratios were used, 2 and 3, both with the same hydraulic diameter. The array was tested at Reynolds numbers from 300 to 1500 and impinging distances of 1 to 5 hydraulic diameters. Thermochromic liquid crystals wee used to map the local heat transfer coefficient using a transient method, while the jet temperature was kept constant. The liquid crystal images were recorded through an optical fiber coupled with a CCD camera and a frame grabber and analyzed based on an RGB-temperature calibration technique. The results are reported relative to the unit cell that is used to delimitate the central jet. The heat transfer variation is shown to depend on the impingement distance and Reynolds number. The elliptic jets exhibit axis switching, jet column instability and jet swaying. All of these mechanisms affect the enhancement of the heat transfer rate and its distribution. The results are compared in terms of average and local heat transfer coefficients, for both major and minor planes for the two jet aspect ratios.

Self-organized feature map algorithm and the classical particle tracking technique have been adopted together to analyze the single-exposure double-frame particle images for flow measurement. Similar to the normal correlation technique in PIV, the whole region is divided into many small interrogation spots. Instead of applying the correlation algorithm to each of these spots to get their rigid translation, the self-organized feature map algorithm is used to compress the information such that every spot is represented by three coded equivalent particles.After tracking these three particle, a linear distributed velocity function can be obtained at every spot. The spot can contain ont only translation,but also rotation, shear and expansion while there is only rigid translation in the spot assumed in the commonly used correlation method. In addition to the theoretical explanation, the suggested method has been verified by a number of digital flow fields which have randomly distributed synthetic particles.

One of the major technological difficulties in implementing digital particle image velocimetry (PIV) is associated with acquiring, processing and storing large volumes of image data form high resolution CCD camera(s). Current CCD camera technology provides both very high resolutions and high frame rates typically producing tens of megabytes of data per second. With the need for simultaneous data form two or more image sources the problems of data transmission, processing and storage become extreme. Significant increases in transfer, processing and storage can be achieved by compressing images by removing components of the image that are redundant or of low significance. This paper presents an approach to PIV image compression and methods of processing encoded data. The effect of varying levels of compression on data transfer and processing rates as well as measurements precision is considered and illustrated with results from both real and synthetic image data.

The shape of the ocean surface on a millimeter scale controls the scattering of microwave radiation, hence the measurement of oceanic properties by remote sensing. In addition the micro-turbulence immediately adjacent to the sea surface brings about transfers of momentum, soluble gases such as CO₂, and heat or water vapor through the lowermost layers of air and the water immediately below. Although these processes are of vital importance to our understanding of the oceans and climate, they have not been adequately studied at sea. Recent developments of optical techniques have greatly simplified measurements of small scale fluid motions and have made them accessible to measurement from a small raft in the open sea. A contributing factor in these developments is the availability of high power, high efficiency visible light diode lasers and high resolution CCD arrays. Optical methods have the advantage that they do not influence the delicate motions of capillary waves at the sea surface, nor are they intrusive in the motions of small turbulent eddies. Our light source for study of turbulence below the water surface is a diode bar laser array. Light generated by the laser array is refracted into a fan shaped light sheet of approximate dimensions 50 by 20 by 2 mm to illuminate particles in the water. Sea water is sufficient transparent to this deep red light that particle tracking and particle image velocimetry can be carried out. The laser and a CCD camera in their water proof containers are so compact that they do not materially interfere with the water flow despite being mounted below the sea surface.

Light-in-flight recording by holography is an ultrafast gating viewing technique that can produce a continuous, frameless motion picture of picosecond laser pulses as they pass by. When the pulses pass through a volume full of scattering particles their 4D shape, spatial and temporal, can be recorded. If instead the shape of the pulse is pre- known the position and velocity of the particles can be recorded in thin sections through the total volume.

Interferometry has always been a powerful tool to diagnose the response of liquids, when changes of status parameters induce modifications in their optical properties. Interferometric measurements are based on the ability to measure variations, around a reference configuration, in the optical path length or the refractive index. Investigations done so far on heat convection driven by capillary forces, indicate that the observation of both the bulk phase and of the free surface, is instrumental for the understanding of the physical mechanisms steering the heat transfer phenomena in 'weightless liquids'. When used in space application, conventional interferometers suffer of some fundamental drawbacks, because of the severe requirements in terms of mechanical stability of the optical elements. Holographic interferometry removes the most stringent limitations of classical interferometry, but requires precise positioning of the recording plate, with accuracy better than half a wavelength. The superior feature of an electronic speckle pattern interferometer (ESPI) is that it enables real time correlation fringes to be recorded by a video camera and displayed on a television monitor, without recourse to any form of photographic processing or plate relocation. This comparative ease of operation allows the technique of ESPI to be extended to considerably more complex problems of deformation analysis and measurement of refractive index modulation. Since it basically works as a time differential interferometer, measurements can always be referred to a well known configuration and condition of the test sample, reducing or even eliminating the requirements on mechanical stability. This paper describes how double-path ESPI are accommodated within the optical diagnostics of a microgravity payload, fluid physics facility, due to launch in 1998 on the Russian retrievable capsule FOTON. The two- ESPI layout permits one to observe and quantify the deformation of the free surface of a liquid subjected to a thermal gradient.Motions induced by the convective flows in the bulk phase can be monitored at the same time. The main features of the ESPI are presented together with design outlines and optical performances.

Phase unwrapping algorithms used in phase-shift or Fourier transform techniques can be classified typically into two groups: line-based unwrapping and region-based unwrapping. Theoretically, the latter can be less error susceptible than the former. However, the pixel categorization process required in the previous region-based algorithms, utilizing the local information obtained from 3 by 3 pixels, is still error prone in many interferograms contaminated by large- scale noises. In the new approach, the developed expert system intelligently find 2 (pi) jump iso-phase lines that categorize regions having no phase jump based on global/regional information rather than the local information, that is, interferogram-specific knowledge. Then it performs phase unwrapping region by region by adding or subtracting 2 (pi) phase-wrapped band wherever region changes. The regional phase unwrapping isolates noises inherently without propagation, since every pixel's phase is unwrapped independently each other. The new algorithm is also effective especially in handling large-scaled noise- affected phase distributions.

A 3D thermal field has been analyzed using a rotating interferometer. By rotating, the interferometer the multi- direction interferograms of the tested field are captured by a CCD-computer system and stored into computer. After processing multi-direction interferograms by the image- processing and reconstruction software the multi-direction data are obtained. The multi-layer thermal field distributions are reconstructed using the same software. All process is finished within a few minutes and a complete 3D thermal field is obtained. The result is well fit to the conclusion gained by thermocouple.

In the present investigation, an optical corrosion-meter has been developed for materials testing and evaluation of different corrosion phenomena. The idea of the optical corrosion-meter was established based on principles of 3D- holographic interferometry for measuring microsurface dissolution, i.e. mass loss, and on those of electrochemistry for measuring the bulk electronic current, i.e. corrosion current of metallic samples in aqueous solutions. In the present work, an early stage of pitting corrosion of a pure copper and an aluminium-brass alloy in tap water was monitored in situ by the optical corrosion- meter during the cyclic polarization test. The observations of pitting were basically interferometric perturbations detected only on the surface of the pure copper in tap water. The interferometric perturbations interpreted as a localized corrosion in a form of an early pittings, of a depth ranged between 0.3 mm to several micrometers. Consequently, results of the present work indicate that holographic interferometry is very useful technique as a 3D- interferometric microscope for monitoring pittings at the initiation stage of the phenomenon for different metallic samples in aqueous solutions.

Density field of Mach reflection of shock waves was investigated by a laser speckle method. A 2D wedge was mounted on the test section of shock tube. When a plane shock wave attack the wedge, shock wave is reflected by the wedge and Mach reflection takes place. Density gradient in the internal region behind the reflected shock wave was measured by this method. The gradient of density plays an important role to determine the reflected shock configuration, especially in weak Mach reflection. Not only the non-uniformity might be a reason 'von Neumann paradox', but also should be important in the case of moderate Mach number. In the present report, density field near the triple point was studied mainly. Optical arrangement is the same as that in Erbeck and Merzkirch. A shock tube and YAG laser were employed in the experiment. The reference and flow fields were recorded in a film. The speckle photographs were processed by auto-correlation analysis by a computer. Displacement of speckle pattern was convected to the density by using a deflection angle-density gradient relation. It was found that the distribution of density field has large gradient near the reflected shock wave. Experimental density fields were compared with numerical results.

For optical diagnostics of fluid mechanics and thermal flow it is difficult to use holographic interferometry or digital speckle pattern interferometry under the harsh engineering environments because there are various disturbances in two dividing coherent beams caused by ambient refractive-index change, optical component disturbance, etc. The digital shearing speckle pattern interferometry (DSSPI), proposed in this paper, uses the interference phenomena between two objective means which pass through a slightly different area in space. In this paper, the experimental arrangement and basic principle of the digital shearing speckle pattern interferometry using optical polarization phase shift are presented in detail. The mathematical models of experimental DSSPI data processing for 2D and axis-symmetrical flow fields are proposed respectively. The technique of the optical polarization phase shift is described to extract quantitatively the phase information form shearing speckle interferograms. Compared with PZT phase-shifter, the optical polarization phase-shifter is more convenient because it does not need a complex calibration. Last, the shearing speckle interferograms and phase images for a candle flame and a natural convection of a heated vertical cylindrical tube are presented. The research show that the DSSPI is an ideal observation and measurement technique for optical diagnostics of fluid mechanics and thermal flow.

A new tomographic algorithm termed Curvilinear Nonlocal Basis Function Method (CNBFM) is formulated and tested for several different computer-generated fields. In addition, the performance of the hybrid method combining the CNBFM and the previously-developed complementary field method is also tested for the same fields. A holographic interferometric tomographic experiment is designed to apply the developed techniques for reconstruction of a 3D temperature field generated by a thermal plume with an aircraft forebody model inside the flow. Reconstruction results are compared with the corresponding thermocouple readings to check the accuracy of the technique. All the fields form the numerical simulation and the experiment are reconstructed under ill- posed conditions, i.e., limited view angle and incomplete projection. It appears that the developed method can substantially enhance the reconstruction accuracy and resolution in real applications of interferometric 3D flow measurements.

In the framework of ESA's FluidPac satellite mission, we have developed a fast, lossy image compression algorithm (ICA) based on a slight variation of the classical 2D FFT. In essence, given a monochrome picture, the ICA calculates its Fourier spectrum. It then applies a low-pass filter to eliminate all Fourier coefficients beyond a certain user- defined cutoff frequency. Finally, it further compresses by encoding the surviving FFT coefficients in more memory- efficient manner. The proposed scheme works best with pictures where the high-frequency data are of little value. This is precisely the case with electronic speckle pattern interferometer images. The ICA's low-pass filter gets rid of the speckle noise while preserving the useful scientific information: the interference fringe pattern. We have, however, also applied the FluidPac ICA to pictures generated by classical interferometers, photographic equipment, particle tracing instruments, and IR cameras. The results are extremely encouraging.

Artificial neural networks can be used to process patterns corrupted by the laser speckle effect. This paper discusses an examples where neural networks were used to detect structural damage using characteristic fringe patterns as input. The artificial neural networks were trained with fringe patterns generated from a finite element model and a simple model of the laser speckle effect. The neural networks were tested on patterns generated by both models and real structures. The neural networks are being developed as high-speed processors for electronic holography. This paper quantifies the overhead required to make neural networks robust to the laser speckle effect. There is a discussion of the ability of these networks to generalize at finite element resolutions on the underlying fringe patterns. The ultimate objective is to test whether combinations of electronic holography and neural networks can be effective interfaces between computational models and experiments or tests.

The optical computer tomography has long been puzzled by how to obtain enough multi-direction data. The multi-channel interferometer is a better solution and has been sued for may examples. It still has many shortcomings such as too complex, difficult to adjust and expensive. A rotating interferometer has been developed to overcome those shortcomings. The interferometer has been placed on a rotating platform and in the rotation center is a fixed platform to place the tested object. By rotating the platform, theoretically infinite directions' data can be obtained. After the system has been adjusted the data of every direction have unique scale that is also superior to multi-channel interferometer which is very difficult to get a unique scale.

A mutually pumped phase conjugator generates a phase- conjugate replica for each of two mutually incoherent incident optical beams interacting within a photorefractive crystal. This operation is useful for optical communication and interferometry. In this paper, we report a demonstration of mutual phase conjugation for light reflected from a diffuse surface. We studied the dependence of the phase- conjugation reflectivity on the parameters of the optical system. Finally, we built a mutually phase conjugating interferometer to detect the ultrasound vibration of a diffuse object to inspect defects inside it, based on laser generated ultrasound technology. The experimental results and analysis will be given.

There are may phase unwrapping algorithms have been developed in the recent years. Some of them work well in no or less noisy situations. But when encountering noisy data which is the most occurring situation these algorithms may exhibit insufficiency and diversity and usually cause the result unusable. Artificial neural networks have some features in tackling these problems. Especially random artificial neural network is more powerful and robust in solving combinatorial optimization problems. A random artificial neural network model has been used in demodulation of 'wrapped phase' in one and two dimensions of noisy interference pattern.

The study of a self-excited compressible jet using single and double-pulsed, phase-shifted interferometry in conjunction with a 9 beam tomographic illumination system is described. A plane wave holographic interferometer using a pulsed ruby laser has been adapted to provide multiple illumination directions of a volume that is approximately 4 centimeters on a side. This set-up is being used to study the transient behavior of compressible jets and may be operated using double-exposure holographic interferometry to study the instantaneous behavior of the flow; alternatively, the system may ge operated in a double-pulse mode to study the fluctuations in the flow. The tomographic reconstructions are made using a Fourier-Bessel expansion. To illustrate the performance of the system, an oscillating pipe-collar nozzle flow producing a wavy flow pattern was studied. The instantaneous measurements show the flow to be oscillating in one plane, whereas from the differential results it is found that this plane is rotating during the oscillation period.

Despite the rapid proliferation and increased capabilities of computational fluid diagnostic algorithms, there still exists a need for experimental techniques which can provide global information in an accurate and expeditious manner for augmentation and/or verification of numerical methods. While many optical, non-intrusive techniques such as particle imaging velocimetry have been developed and refined in recent years, systems which can simultaneously extract all three-velocity components are few. We present a technique which utilizes a dual-reference-beam holographic recording and reconstruction system along with a two-step data acquisition and processing method for the determination of in- and out-of-plane velocity components form a single viewing direction. Although still under development, the method, termed holographic diffraction image velocimetry, shows promise to become a useful tool for accurate gross-field diagnostics of complex flows.

A multiplexed diode-laser absorption sensor system, comprised of two distributed feedback (DFB) InGaAsP diode lasers and fiber-optic components, has been developed to non-intrusively measure gas temperature and H₂O concentration over a single path in the combustion region of a 50-kW model pulsed incinerator. The wavelengths of the DFB lasers wee independently current-tuned at 10-kHz rates across H₂O transitions near 1343 nm. Temperature was determined from the ratio of measured peak absorbencies and used for closed-loop control of the combustor. In addition, measurements of CO, CO₂, and C₂H₄ concentrations were determined from absorption spectra recorded in the incinerator exhaust using a fast-sampling stainless steel, water-cooled probe and a multi-pass absorption cell. An external cavity diode laser was tuned over the CO R(13) transition near 1568 nm and the CO₂ R(16) transitions near 1572 nm, and a DFB laser was tuned over selected C₂H₄ transitions near 1646 nm. A correlation was established between the magnitude of the observed temperature fluctuations and the measured CO concentration in the exhaust. The amplitude of temperature fluctuations was controlled in a feedback loop by adjusting the relative phase between the primary and secondary forced air flows. The results obtained demonstrate the applicability of multiplexed diode laser absorption sensors for rapid, continuous measurements and control of multiple flowfield parameters, including trace species concentrations, in high- temperature combustion environments.

In recent years, laser based optical techniques have been extensively used in industry to investigate flow. The main application areas vary from complex flow fields in rotating turbo machines to complicated two-phase gas/liquid and liquid/liquid flows. Several measuring systems, based on optical techniques, are commercially available which include laser doppler system, phase doppler system, laser diffraction system and scanning laser microscope. The choice of the measuring system mainly depends on the information required and the nature of flow involved. This paper describes the limitations and the general problems of some of these measuring techniques. Results from several experimental rigs have been presented and in some cases measurements from two different optical systems have been compared for identical flow conditions. The discrepancy in results have been explained to justify the use of these techniques.

In this paper a technique of visualizing flow field in diesel combustion chamber is presented. It consists of laser source, moire deflectometer and high speed camera. Using this setup to visualize the flow field in a single chamber diesel, we gained the series deflectograms of flow field under different conditions and calculate the temperature distribution of its flow field quantitatively.

The flight environment of next-generation theater missile defense interceptors involves hypersonic speeds that place severe aero-thermodynamic loads on missile components including the windows used for optical seekers. These heating effects can lead to significant boresight error and aberration. Ground-based tests are required to characterize these effects. We have developed methods to measure aberrations in seeker windows using a Shack-Hartmann wavefront sensor. Light from a laser or other source with a well known wavefront is passed through the window and falls on the sensor. The sensor uses an array of micro-lenses to generate a grid of focal spots on a CCD detector. The positions of the focal spots provide a measure of the wavefront slope over each micro-lens. The wavefront is reconstructed by integrating the slopes, and analyzed to characterize aberrations. During flight, optical seekers look upstream through a window at 'look angles' angles near 0 degrees relative to the free stream flow. A 0 degree angle corresponds to large angles approaching 90 degrees when measured relative to the normal of the window, and is difficult to simulate using conventional techniques to illuminate the wavefront sensor during wind tunnel tests. For this reason, we developed a technique using laser- induced optical breakdown that allows arbitrary look angles down to 0 degrees.

Both fluctuations of local velocity and local temperature were measured in a steady turbulent diffusion flame of propane by using the semiconductor laser 2-focus velocimeter and the optical fiber thermometer and the optical fiber thermometer respectively. The flame temperature and the soot particle density were calculated by applying the IR two- color method to the measured radiant energy from the soot particles in the flame. In the analysis of the frequency power spectra of temperature and velocity fluctuations, the correlation-based slotting technique was adopted for those data with the nonuniform time interval. It is shown that the time mean value and the fluctuation of the flame temperature decrease gradually toward downstream in the luminous flame region, and those of the soot density increase due to decay of turbulence along the flame axis. On the other hand, both time mean and fluctuation of the flame temperature increase in the radial direction from the center to the periphery due to the effect of air entrainment marked in the peripheral region of the flame. Furthermore, the power spectrum of the velocity fluctuation is not always the same as that of the temperature fluctuation in the flame center.

A new line-of-sight technique based on single exposure speckle photography is described that allows to measure the temperature fluctuations as well as the degree and direction of anisotropy of turbulence in a turbulent flow. To perform quantitative specklegram evaluations, a direct numerical simulation of the light tracing trough the turbulence is performed. Under assumption of geometrical optics the rays paths through the 3D turbulent field are computed from the ray equation. The 3D field of the index of refraction is prescribed on a numerical grid using data of direct numerical simulation of turbulent shear flows. As a result, the evaluation procedure of the 3D correlation function of turbulence reconstruction using 2D speckle photography data was developed and tested. An extension of the technique into a streak mode is described and an example of temporal evolution of turbulence in non-steady flow is presented.

The evolution of the spatial profile of a thermal lens induced by a cw low power laser beam in an absorbing dye solution is directly visualized in real time using glow- coherence light interferometry. Both spatial characteristics and response times of the lens are measured. Preliminary comparisons between experimental result and thermal diffusion theory are presented. The accuracy of measured refractive index in the thermal lens profile is better than 10^-6.

This paper deals with the digital numerical reconstruction of Young's fringes from laser speckle photography by means of the Fresnel-transformation. The physical model of the optical reconstruction of a specklegram is a near-field Fresnel-diffraction phenomenon which can be mathematically described by the Fresnel-transformation. Therefore, the interference phenomena can be directly calculated by a microcomputer.If additional a CCD-camera is used for specklegram recording the measurement procedure and evaluation process can be completely carried out in a digital way. Compared with conventional laser speckle photography no holographic plates, no wet development process and no optical specklegram reconstruction are needed. These advantages reveal a wide future in scientific and engineering applications. The basic principle of the numerical reconstruction is described, the effects of experimental parameters of Young's fringes are analyzed and representative results are presented.

Beam-deflection optical tomography was applied to measure the 2D temperature field of a turbulent hydrogen diffusion flame. The temperature distribution calculated with a filtered back-projection algorithm agrees well with the result of a temperature measurement using Raman spectroscopy. This was proved with a high number of projections. For enclosed flames wit restricted optical access and in the case of time-continuous measurements, however, the number of sampling points and viewing directions is limited. In this case, algebraic reconstruction techniques are well suited for tomography. These algorithms have been adapted for temperature measurements in flames by laser beam deflection. Experiments and simulations were performed to estimate the spatial resolution and accuracy with a varying number of input data.

The theory and experimental method of measuring flame temperature field with two-reference phase-shifting holographic interferometry and CT technique are studied in this paper. By recording the relative intensity distributions of three-step phase-shifting each view direction, we obtained the accurate phase distributions used to reconstruct the refractive index field. The cross section temperature field of a double-candle flame is measured, and the sources of experimental and other error are also discussed.

Particle Image Velocimetry and Particle-Tracking Velocimetry have been successfully used for measuring instantaneous velocity fields. Analyzing PIV images involves matching particle images captured sequentially. Correlating interrogation images is commonly used, which determines the non-rotational rigid body motion of interrogation image elements by averaging motions of a sufficient number of particles within the interrogation element. A variety of methods are used for PTV which tracks the motions of individual particles. In PTV applications, particle seeding density is kept low to avoid ambiguity of multiple particles within the interrogation element.PIV allows for higher particle seeking. However, each interrogation element has to be large enough to include a significant number of particles. Both PIV and PTV data processing methods limit the ability of extracting fine spatial scale flow motion from particle image data. The feature-based matching method proposed recently bridges the methods of PIV and PTV. It enables us to track individual particles at higher particle seeding,thus is capable of detecting flow motion at a smaller spatial scale. The feature-based matching method has been evaluated on different data sets. It shows the fine structure of flow field by the motions of each particle and its neighborhoods. Spatially averaged velocity fields are consistent with those calculated from image correlation methods.

A non-intrusive optical system for the measurement of air inlet condensation in gas turbine engines is presented. The system uses a technique in which a linear relationship between the liquid water content (LWC) and the optical extinction coefficient exists. The extinction coefficient was determined by measuring the extinction of a 10.6 micrometers CO₂ laser beam due to Mie scattering from water droplets and the LWC calculated from the linear relationship. Results of the extinction coefficient determined with the system used in a single transmission path mode on a condensing flow occurring in the inlet of a subsonic suction tunnel are presented together with the temperature rise of the ambient air calculated from the extinction coefficient. A rise of 8.65 degrees K was obtained at 0.65. Mach, for an ambient temperature of 20 degrees C and relative humidity 49 percent, which is consistent with previous non-optical measurements.

We describe here a multifunctional plasma diagnostic (MFPD) device being developed by Physical Optics Corporation using interferometry and spectroscopic techniques, along with an intelligent software package. The MFPD can provide a non- contact diagnosis of plasma density profile, temperature profile, and ionic species of plasmas. High-speed data processing is accomplished through automatic data acquisition hardware and an intelligent software package, which contains two major parts: (1) a genetic-algorithm- based, fast-evolved phase profile fitting program, and (2) an intelligent neural network spectral feature recognition and plasma classification routine. The integrated MFPD is user-friendly, real-time, simple to operate, and applicable to industrial environments.

In this paper a digital speckle pattern interferometry (DSPI) based on an optical polarization phase shift for measurement of temperature fields in thermal flow is presented. First, the principle and physical-mathematical models of the phase shift digital speckle pattern interferometry (PSDSPI) are proposed. Second, the experimental arrangement of PSDSPI is described. Third,the effects of experimental parameters on PSDSPI, e.g. spatial location of speckle source, intensity ratio of objective to reference beam, F-number of image lens and angle between objective and reference beam are analyzed in detail. Finally, some experimental results are presented. The PSDSPI is based on optical polarization phase shift technique, which uses a quarter-wave plate and a plane polarizer. When the relative position between the quarter-wave plate and the polarizer is rotated, a phase shift can be introduced. Comparing to piezoelectric transducer phase shift device, the optical polarization phase shift is more convenient, because no complex calibration is needed. As an application example PSDSPI is used for temperature field measurements in a natural convection flow generated by a heated vertical plate. The investigations show that the PSDSPI is a fast and real-time measurement method for optical diagnostic of thermal flow.

A liquid/liquid system has been used to model high pressure gas/liquid systems. Kerosene and aqueous potassium carbonate solution have been chosen for his purpose. An experimental facility has been constructed in which horizontal and vertical liquid/liquid flows can be investigated. The main objective of the work is to gather information about the drop size distributions of the dispersed aqueous phase which is important for modeling such flows. Two different optical system were employed in horizontal and vertical flow positions. Laser results obtained for various flow conditions have been compared with the existing data.

Laser induced predissociative fluorescence is often used for diagnostics because its short-lived upper states are minimally disturbed by collisions. We discuss here the effects of lower-state collisions using parameters relevant to atmospheric flames. A simple model, with no adjustable parameters, produces a reasonable fit to the data. It predicts that, even at very modest laser energies, the fluorescence intensity is almost directly proportional to the rate constant for rotational energy transfer (RET) within the lower vibrational states. Here we present calculations that show that the ratio of LIPF signals from two rotational states, and thus the deduced temperature, is very sensitive to laser intensity. The conversion of a measured fluorescence ratio to temperature is particularly difficult, because RET rates can be a function of local conditions and of the laser is also important.

An experimental demonstration of fiber optic temperature sensing in the in-core region of Japan Materials Testing Reactor from 250 to 750 degrees C is described. Temperature data could be obtained for two full-power weeks with neutron fluxes of approximately 10¹⁴ n/cm²/s and gamma dose rates of approximately 5 X 10³ Gy/s. The measurements were based on thermally generated IR light within the optical fiber itself. The fiber thus served as both signal generator and signal transmitter to the out-of-core region. The fibers utilized in the experiments where of high OH pure-silica-core type and showed good radiation resistance. In the IR region the transmission of the fibers was only weakly affected by the incident radiation. Radiation induced luminescence and Cerenkov radiation in the optical fibers were found to have small influence on the signal in the IR window. The high OH content of the fibers used in the present experiment precluded the use of the spectral regions at 945, 1245, and 1390 nm, due to the high intrinsic and radiation induced absorption at these wavelengths. The use of silica fibers limited the maximum temperature to < 1000 degrees C. The present experiments show that optical sensors based on IR emission can be used to monitor temperature in the in-core region of nuclear reactors for extended periods of time.

Optical diagnostics are important to the developments of heat and mass transfer studies at Belarus Heat and Mass Transfer Institute (HMTI). The present paper gives a brief account of some of the developments at the HMTI. A considerable effort is devoted to image analysis and experimental data processing with extensive use of computers, both local and those successfully functioning as a united net at the Institute.

We have performed non-intrusive thermometry in rich ethylene/air flames using a frequency measurement based on laser-induced gratings. Light from a cw probe beam is coherently scattered from a thermal or electrostrictive grating induced by the pulsed pump beams. The Doppler modulation of the signal beam is determined by the local speed of sound from which a temperature can be extracted. Soot particles, acting as blackbody absorbers do contribute to the signal.

Filtered Rayleigh Scattering and shadowgraph flow visualization were used to characterize the penetration of helium or moist air injected transversely at several pressures to a Mach 3 flow in the NASA Lewis 3.81 inch by 10 inch continuous flow supersonic wind tunnel. This work is in support of the LOX augmented nuclear thermal rocket program. The present study used an injection-seeded, frequency doubled Nd:YAG pulsed laser to illuminate a transverse section of the injectant plume. Rayleigh scattered light was passed through an iodine absorption cell to suppress stray laser light and was imaged onto a cooled CCD camera. The scattering was based on condensation of water vapor in the injectant flow. Results are presented for various configurations of sonic and supersonic injector designs mounted primarily in the floor of the tunnel. Injectors studied include a single 0.25 inch diameter hole, five 0.112 inch diameter holes on 0.177 inch spacing, and a 7 degree half angle wedge. High speed shadowgraph flow visualization images were obtained with several video camera systems. Roof and floor static pressure data are presented several ways for the three configurations of injection designs with and without helium and/or air injection into Mach 3 flow.

Particle laden flows are encountered in many fossil fuel and industrial processes such as the gas-solid flows in power plants, liquid-solid flows in coal and grain transportation and gas-liquid flows in combustors. These flows are not well understood, thus computational fluid dynamic modeling of these system has been hampered. Fundamental measurements are required to study the motion of the different phases to obtain an understanding of these flows and to develop reliable models. No reliable non-intrusive methods are available to fully characterize two phase flow fields, i.e. obtain particle size, velocity, concentration and concentration gradients at the same time over an extended area of interest. Intrusive sampling methods compromise the two phase flow field making the measurements suspect. Conventional optical methods do not disturb the flow but provide local point wise velocity measurements only. Particle size can be obtained for only spherical particles using the phase Doppler interferometric methods.

Wave propagation in inhomogeneous media has been studied for such diverse applications as propagation of radiowaves in atmosphere, light propagation through thin films and in inhomogeneous waveguides, flow visualization, and others. In recent years an increased interest has been developed in wave propagation through shocks in supersonic flows. Results of experiments conducted in the past few years has shown such interesting phenomena as a laser beam splitting and spreading. The paper describes a model constructed to propagate a laser beam through shock-like inhomogeneous media. Numerical techniques are presented to compute the beam through such media. The results of computation are presented, discussed, and compared with experimental data.

The approach to so-called ideal observation and measurement technique or instrumentation (IOMT) will be described and discussed for the fluid mechanics. The full field observation and measurement technique system (FFOM) should be an advance techniques and the new generation of the experimental technique or instrumentation which will across the new century to close to IOMT. The concept of FFOM was described and discussed. The trace and trend of FFOM techniques and their application in the fluid mechanics were summarized. Also some work about those techniques and application in BUAA were introduced.

A 3D measurement is presented of both the in-plane and out- of-plane components of the flow field velocity of 0.5 micrometers styrene particles at 30 ms^-1 in air from a calibrated nozzle by using a co-linear side scattering PIV approach. The light sheet used to illuminate the particles was generated using a Nd:YAG laser, operating in triple pulse mode. The scattered light from the particle was imaged through a near diffraction limited lens. The particle images have been analyzed from both their respective diffraction patterns and from their out of focus intensity profile. The authors show that the co-linear 3D PIV method can be used to determine the particle velocity in three directions. Results have been presented for different flow angles through a calibration 30ms^-1 air jet, showing that it is possible to identify the particle position in three directions, within a turbulent flow, to a spatial accuracy of +/- 20 micrometers .

To further understand the effect of both compound angle holes and hole shaping on film cooling, detailed heat transfer measurements were obtained using hue based thermochromic liquid crystal method. The data were analyzed to measure both the full surface adiabatic effectiveness and heat transfer coefficient. The compound angles that were evaluated consist of holes that were aligned 0 degrees, 45 degrees, 60 degrees and 90 degrees to the main cross flow direction. Hole shaping variations from the traditional cylindrical shaped hole include forward diffused and laterally diffused hole geometries. Geometric parameters that were selected were the length to diameter ratio of 3.0, and the inclination angle 35 degrees. A density ratio of 1.55 was obtained for all teste. For each set of conditions the blowing ratio was varied to be 0.88, 1.25, and 1.88. Adiabatic effectiveness was obtained using a steady state test, while an active heating surface was used to determine the heat transfer coefficient using a transient method. The experimental method provides a unique method of analyzing a three-temperature heat transfer problem by providing detailed surface transport properties. Based on these results for the different hole geometries at each blowing ratio conclusions are drawn relative to the effects of compound angle holes on the overall film cooling performance.

A system to measure gaseous hydrocarbon distributions was devised, which is based on IR light absorption by C-H stretch mode of vibration and computed tomography method. It is called IR-CT method in the paper. Affection of laser light power fluctuation was diminished by monitoring source light intensity by the second IR light detector. Calibration test for methane fuel was carried out to convert spatial data of line absorption coefficient into quantitative methane concentration. This system was applied to three flow fields. The first is methane flow with lifted flame which is generated by a gourd-shaped fuel nozzle. Feasibility of the IR-CT method was confirmed through the measurement. The second application is combustion field with diffusion flame. Calibration to determine absorptivity was undertaken, and measured line absorption coefficient was converted spatial fuel concentration using corresponding temperature data. The last case is modeled in cylinder gas flow of internal combustion engine, where gaseous methane was led to the intake valve in steady flow state. The fuel gas flow simulates behavior of gaseous gasoline which is evaporated at intake valve tulip. Computed tomography measurement of inner flow is essentially difficult because of existence of surrounding wall. In this experiment, IR laser beam was led to planed portion by IR light fiber. It is found that fuel convection by airflow takes great part in air-fuel mixture formation and the developed IR-CT system to measure fuel concentration is useful to analyze air-fuel mixture formation process and to develop new combustors.

The adverse impact of chlorofluorocarbons (CFCs) on stratospheric ozone has prompted an international effort for replacement with environmentally acceptable alternatives such as hydrogen-containing chlorofluorocarbons (HCFCs). Previous studies of the reactions of OH and HCFC were limited to 298 K or below. Rate coefficients are needed above 480 K to verify the existing theoretical interpretations. Kinetics study of OH and HCFC reactions over an extended temperature range is revealed by LP/LIF technique. Based on the experimental data, the conventional transition state theory with the assistance of ab initio calculations is used to predict the reactions above 2000 K. A methodology is evolved from the precision measurements and the reliable theoretical studies.

The use of a fluorescent dopant molecule to enhance the natural fluorescence of motor oils, and allow quantitative determination of temperature and film thickens in internal combustion engines has been investigated. Measurement of the fluorescence as a function of temperature were made with neat Mobil 1, and solutions of the dopant BTBP in mineral oil and Mobil 1. The fluorescence yield of neat Mobil 1 was found to vary by 30 percent over the temperature range explored, but the spectral characteristics, as measured with bandpass filters, were unaffected by temperature. The BTBP fluorescence was found to increase significantly with temperature, and it was found the narrower regions in the spectrum increased proportionally more than the fluorescence collected over the entire spectrum, allowing a determination of temperature to be made which can then be used to correct for the change in fluorescence yield. Solutions in Mobil 1 showed a smaller increase than that observed in mineral oil.

Using a narrow band, frequency-doubled output of a pulsed- dye-amplifier, simultaneous absorption and laser-induced fluorescence measurements of OH have been performed to study the rotational dependence of the collisional quenching of the OH fluorescence emission from 2(Sigma) + levels due to water molecules. In these studies, the OH was produced in a low pressure water vapor microwave discharge cell. The microwave power was varied in the range between 30 to 50 Watts in order to investigate variations in the quenching rate, translational, and rotational temperatures with microwave power. From the absorption lineshape data, it was determined that, for a given microwave setting, the OH molecules in the region of excitation are in both rotational and transnational thermal equilibrium. The quenching results indicate a slight variation with increasing microwave power. They also show a variation with the excited rotational level. For K > 4, the quenching rate decreases as the rotational level excitation increases. This is in agreement with previously observed trends. Finally, the quenching rate data obtained in this study are compared to those available in the literature and discrepancies are discussed.

Intracavity laser absorption spectroscopy was used to study concentration profiles of several radicals in flames. Very high sensitivity of ICLAS enables quantitative measurements of absolute concentrations of atoms and radicals in flames. MOst of the experiments were done with a flat flame burner placed inside the cavity of a broad band dye laser. The spectra of HCO radicals and CH₂ radical, in the singlet electronic state were measured with a high signal-to-noise ratio at different position above the burner.In this work we report the measurement of the concentration profiles of HCO and CH₂ radical sin methane/air flame. The spectra of these two radicals can be measured simultaneously which is advantageous in combustion diagnostics. Cavity ring-down laser spectroscopy was used to measure the OH concentration profiles of the HCO and OH radicals are in reasonable agreement with computer simulation results. However, a rough estimation of the CH₂ absolute concentration indicates a much higher concentration than that which can be predicted based on the model calculation.

Filtered Rayleigh scattering using iodine absorption cells is an effective technique for obtaining density, temperature, and velocity measurements in high speed confined flows. By tuning a single frequency laser to a strong iodine absorption line, stray scattered laser light can be greatly suppressed. For example, the minimum transmission predicted by an iodine absorption model calculation is less than 10^-5 at the 18788.44 cm^-1 line using a 200 mm absorption cell containing iodine vapor at 0.46 T. Measurements obtained by other researches using a CW Nd:YAG laser agree with the model calculations. However, measurements made by us and by others using Q-switched, injection-seeded, frequency doubled Nd:YAG lasers only show minimum transmission of about 3 X 10^-3. This greatly reduces the applicability of the filtered Rayleigh scattering technique using these lasers in experiments having large amounts of stray scattered laser light. The purposes of the present study are to characterize the spectrum of the excess light transmitted by the iodine cells and to make changes to the laser to reduce the transmitted laser light. Transmission data as a function of laser frequency for the iodine absorption line at 18788.44 cm^-1 are presented. A planar mirror Fabry-Perot interferometer was used to characterize the frequency spectrum of the light passed through the iodine cell to have a component with a bandwidth of about 40 GHz. This is probably caused by other modes in the laser that exist in spite of the single frequency injection beam A second broadband component was also observed, possibly caused by the laser flash lamps or by fluorescence. An intracavity etalon was installed in the laser oscillator cavity to suppress the 40 GHz component. Measurements taken with the etalon tuned to the injection frequency showed a reduction in the transmitted laser light. This improvement allows the iodine cell to block significantly more of the stray laser light in filtered Rayleigh scattering experiments. Examples are given of filtered Rayleigh scattering measurements showing the effect of the etalon on measurements taken in a Mach 3 flow in the NASA Lewis 4 inch by 10 inch supersonic wind tunnel.

UV-visible multi-channel absorption spectroscopy has been used to probe the self-sustained combustion of pressed RDX, a main energetic ingredient found in modern day propellants and explosives. The two dimensional feature of an intensified CCD detector allowed simultaneous recording of multiple, spatially distinct absorption spectra. Between 10 and 12 equally spaced absorption spectra with spatial resolution as small as 0.163 mm have been obtained during 1 ms exposure. The number of absorption spectra and the spatial resolution can easily be set by the detector software, size of the excitation sheet and the focal length of the collection lens. Temporal resolution in the UV region has been increased to 1 ms by pulsing the light source. A 0.54 joule pulse with a duration of 0.75 ms was added to a simmering Xenon arc lamp for the measurement of combustion species. The increase in light intensity of 30 and 70 times the non-pulsed output provided the necessary light flux to achieve single pulse, multiple absorption spectra. To increase the species concentration sensitivity of the experiment, a triple pass optical arrangement was adopted. Partially silvered windows were installed at an angle to the beam providing for three passes across the samples. The corresponding path length was increased by a factor of 2.8 times the sample diameter. Least squares analysis of absorption spectra provide mole fraction profiles for OH, CN and NH along with temperature. Profiles for NC and HN have been determined for self-sustained combustion of RDX in 1.0, 1.5 and 2.0 atm air. Peak CN mole fractions of about 200 ppm are observed at 1 atm pressure and the NH mole fraction is about a factor of two lower. As the pressure is increased the reactive CN and HN species peak closer to the combusting surface and reside over a smaller spatial extent. Peak concentrations drop for these higher pressures, but may be due, at least in part, to limitations of the spatial resolution of the absorption experiment.

As part of a program to develop methods for imaging combustion processes in engines using tunable excimer lasers, we have studied the pressure dependence of vibrational Raman scattering from nitrogen at pressures up to 60 atm. Tunable, powerful UV-lasers have an advantage over visible lasers because many types of physical light scattering mechanisms can be used with only minor changes of equipment. The intensity of Raman scattering at UV wavelengths is very strong because it varies as the fourth power of the laser frequency. We can simultaneously acquire a 1D image of temperature as well as of the density of all the major constituents. Alternatively we can use line-of- sight Raman in a back-scatter mode in which only tow very small windows are needed for optical access. In order to do all of this, the differential Raman cross section must be shown to be independent of pressure. Since nitrogen is often taken as the reference material, with the Raman cross sections for other gases measured relative to it, we demonstrate the pressure independence for nitrogen.

The goal of the investigation was to develop experimental techniques for measuring the spectra, pressure and gas temperature of transient optical emission from the detonation of exotic materials in a vented chamber. The measurands are important in characterizing the performance of the materials and in optimization of the mechanical and chemical design. A dual branch multi-channel spectrograph was constructed and calibrated to measure both the time- resolved spectral radiation and total spectral energy from the detonation process. An optical trigger system was designed to synchronize the data acquisition system with the detonation of the exotic materials. Fiber optics were used to isolate the spectrography from the vibration of the detonation and to facilitate the optical alignment of the spectrograph. A quartz pressure transducer and charge amplifier were used to obtain the chamber pressure. The indication of gas temperature was calculated on the basis of temperature calibration and the obtained spectral data. A total of twenty different types of materials were tested. The lifetime of the radiation from the detonation of these materials ranged from 600 microseconds to 1.5 milliseconds, and the wavelength ranged from 400 to 1200 nanometers. The radiation was a continuum superimposed by the lines and bands. The gas temperature derived from the measurements was found to be from 2000 to 3000 degrees Kelvin. The experimental techniques developed for this investigation have proved helpful in comparing the performance of the existing materials and for the design of additional materials.

An image analysis method is proposed for space and time correspondence of discrete traveling particles and is intended for a 3D velocity measurement by particle image velocimetry (PIV). In a principle of the PIV, the particles illuminated for fluid flow visualization are tracked during time fixed, and the velocity is obtained by a computational analysis of moving distance and direction of the tracked particles. This study is based on a thought that the purpose of particle tracking is accomplished by space and time correspondences of the particles The time correspondence is a combination process to find identical particles from particle distributions in two optical images captured with the time difference. Also the space correspondence is a combination process to find identical particles from plural images captured in more than two directions at same time. This process is a suitable image analysis for space position measurement of particles, it is though that the analysis method becomes a conventional technique overcoming the difficulty. In this method, the particle velocity is directly obtained from an optimum correspondence of the discrete particles in space and time. This study devises an application of genetic measurement of particles flowing around a rectangular column and shows the effectiveness of 3D image analysis with genetic algorithms.

A 2D droplet sizing technique is applied to measure the diameter of droplets present in an engine chamber before the combustion process. This technique is based on the evaluation of the number of fringes due to the interference between the laser light reflected by the droplets and the light refracted. Usually, the collection optics are placed between 30 degrees and 80 degrees of the laser beam. The main interest of this paper is that this technique is applied with a forward-scattering angle range around 90 degrees. So, the evaluation of the droplets diameter from the fringe numbers is more difficult due to the low level of the scattered light and to the quasi non-validity of the geometrical approximations. This technique is applied for a droplet diameter range of 5 micrometers to 50 micrometers . In order to improve this particular application of this droplet sizing technique, the comparison with a calibrated spray is done. Finally, this technique will be used in an optical access internal combustion engine, where the pictures will be taken only via the transparent piston head.

The new method is based on the interaction of fast beam electrons with electrons in the outer shells of atoms, which generates the characteristic x-ray radiation. The intensity of x-rays is proportional to the concentration of the atoms in investigated gas. The gasdynamic structures of rarefied argon jets were studied in the range of stagnation temperatures up to 5200 K using the this x-ray method. The experimental studies of the present work were performed in a low-density gasdynamic chamber. The arc heater was used as a gasdynamic source. The changes in the structure of a jet of monatomic gas beyond a sonic nozzle with variation in the rarefaction and the temperature factor have been clarified as a result of the experiments and generalizations performed.

There are two sections in this paper. First, by using physical model of -4- bound, the statistics properties of scattering particles are studied ; the velocity autocorrelations function and the mean-square displacement of scattered particle under our physical model are got ; we discuss the different a values for different bound model. Second, the scatteded electrical field autocorrelation function of dynamic light scattering through bound scattering particles is calculated. The resules of this paper, we think can been compared with resules experiment and a value for different solution may been obtained. Keywords : 4 bound, Brownain particles, DLS.

We study the detectional theory of polydispersities for dilute suspension of optical and size polydisperse spherical particles for which the Rayleigh-Gans-Debye approximation is valid. Tho develop the theory a concentric core-shell hard sphere model is adopted, in which particles possess a continuous variation in the core size and shell thickness. The thickness of shell is directly proportional to the radius of core, thus giving rise to a distribution in the particle refractive indices. We assume the shell thickness L equals (alpha) R, where (alpha) < 1 and is a constant. We extend the 'measured' dynamic structure factor to the general case where optical and size poly-dispersed are combination and a new 'measured' dynamic structure factor to the general case where optical and size poly-dispersed are combination and a new 'measured' static structure factor S^m (K) is derived. We analyze the dependence of the average scattered intensity I(q) and the effective diffusion coefficient D_e(q) which is obtained from the first cumulant measured by dynamic light scattering in the case of the refractive index of the solvent and the refractive index of the shell are matched, i.e., n_{m$ equals n(subscript s}, on scattering vector q. Under favorable conditions it should be possible to measure small polydispersities.

In this paper, taking the effects of avalanche ionization and electron-ion recombination into account, a model for plasma ignition is presented. Assuming the laser pulse has a rectangular temporal shape, an analytical solution of the plasma ignition can be given. Using this model, the dependence of the time needed for plasma ignition on the laser parameters, such as laser power density and laser wavelength as well as the material reflective index can be given.

The process of self-propagating high-temperature synthesis (SHS) has been applied as the new technology for production of construction materials and especial refractories with enhanced strength- and fire-resisting properties. These materials are aimed to be used as synthetic mullits lining refractories in heat units. In the visible light range, the following characteristics of SHS process have been investigated: the localization and the temperature of initiating of SHS process,the propagation of SHS wave on surface- or in volume, velocities of spreading of combustion wave, the number of SHS reaction stages. The visualization with a video-recording of the combustion wave of the SHS process has been performed inside the muffle furnace. The video has been processed with computer card of frame grabber and has been analyzed in multivideo mode, where each frame had been captured in fixed time interval. Thus, several mixtures of SiO₂-Al have been studied by variation of: the SiO₂ particle size,the stoichiometric coefficient, by the substitution of the SiO₂ to ashes and kaolin, and by the adding of supplementary components like Fe₂O₃. The SHS reactions are processed by the preliminary heating to the temperature of 650-860 degrees C. The local thermal self initiating of the SHS process and its propagation in the volume of a sample have been visualized. The multistage SHS reaction has been identified.

We present two novel narrow passband spectral filters capable of frequency resolved imaging of rotational Raman light scattering with strong spectral rejection of out-of- band Raman, Rayleigh and Mie scattering. The first filter, capable of 2D imaging and spectral selectivity, is based on mercury vapor absorption and subsequent resonant florescence. The second filter exploits the variation in the index-of-refraction near resonance to spatially resolve small spectral shifts. It is capable of simultaneous 1D measurements of multiple frequencies. Each filter has a spectral sensitivity of better than 1 cm^-1. The filters are paired with an injection seeded, cavity locked, frequency tripled Ti:Sapphire laser which produces > 30 mJ pulse of single mode, tunable light in the vicinity of 253.7 nm. The laser and resonant fluorescence filter are combined to spectrally resolve scattering form individual rotational Raman lines of nitrogen and oxygen. A description of each filter is given.

Particles measurement systems based on the principles of statistical optics have the potential to be simple and robust as they possess a fundamental method of light intensity calibration and considerable information can in principle be extracted from a single detector. One practical limitation for the application of statistical optics to on- line and in-situ particle measurements is the low fluctuation power. It is shown how the fluctuations may be increased by the use of structured light and a practical demonstration is performed on a flowing suspension of latex particles.

A series of measurement have been made using PIV in the trailing edge region of the stator row and rotor in the annular transonic cascade at RAe Farnborough. The measurements provide an instantaneous quantitative whole field visualization of an unsteady transonic flow interaction region. This work is the first such measurement to be made in a rotating transonic facility.