Experimental and chemical modeling studies of H₂/N₂O/Ar, H₂NH₃/N₂O/Ar, and H₂/N₂O/NO₂/Ar flames are performed to test and refine a detailed chemical mechanism developed in our laboratory. This mechanism consists of 103 reactions and 22 species, and is denoted VS-modified-2. Flame temperatures are measured with a coated, thin-wire thermocouple and by OH and NH laser- induced fluorescence (LIF), whereas species concentration profiles of H₂, NH₃, N₂O, N₂, H₂O, NO, O₂, NH and OH are recorded using molecular beam/mass spectrometry, LIF, or both. The experimental species concentrations are compared to those generated with PREMIX, a 1D, laminar, flame code, using the measured temperature profile and the VS-modified-2 mechanism as input. Overall, laminar, flame code, using the measured temperature profile and the VS-modified-2 mechanism as input. Overall, the PREMIX calculations predict very well the major, species concentrations throughout each flame. For the H₂,N₂O,Ar flame, the postflame O₂, OH, and NO concentrations decrease by approximately 90, 45, and 35 percent, respectively, with the addition of approximately 4 percent NH₃. This decrease is predicted rather well by the PREMIX calculations, which show a decrease in O₂, OH, and NO by approximately 90, 55, and 40 percent respectively. The shapes of the modeled O₂, NO, and OH profiles for the H₂/N₂O/NO₂/Ar flame are in excellent agreement with those observed experimentally. The modeled OH profile even predicts an observed peak at approximately 3 mm above the burner surface. This peak is attributed to the competition between the NO+H equals NO + OH reaction, which produces OH, and the H₂ + OH equals H₂O + H reaction, which consumes it. Rate and sensitivity analyses of the above-mentioned flames are presented discussed.

The prediction of infrared emissions from gaseous plumes is an important tool for remote sensing, heat transfer, and vulnerability assessment. We have developed a software model called 'RAD3D'that generates hyperspectral images of 3D gaseous plumes. The model directly ray-traces through gas volumes input in the PLOT3D format. In addition to single and arrays of lines of sight, the model will automatically generate additional lines of sight to resolve image structure. Outputs of the model include hyperspectral and in-band radiances and transmittances, along with range-to-plume images. Opaque body regions may be embedded within the gas volume.

A diagnostic system using a kHz solid state laser is under development. The system combines a high power diode pumped solid sate laser system as excitation source with an intensified fast scan camera system. The Yb:YAG disk laser oscillator and a regenerative amplifier generate tunable radiation, spectrally narrowed to $DELTA(lambda) < 5 pm, which will be converted by nonlinear crystal into the VIS and the UV spectral ranges. The excitation of the planar laser induced fluorescence of selected molecules and radicals at wavelengths inside the discussed spectral ranges is demonstrated in preparatory experiments. Examples are the OH radical, NO and formaldehyde molecules excited by a frequency doubled dye laser. From these experiments the needed pulse energies of the solid state laser system for light sheet shaping are derived. The system is under development for investigations of combustion processes under reduced gravity at drop tower Bremen, during parabolic flights and at the ISS.

Fluorescence from phosphor coatings is the basis of an established technique for measuring temperature in a wide variety of turbine and combustion engine applications. Example surfaces include blades, vanes, combustors, intake valves, pistons, and rotors. Many situations that are remote and noncontact require the high intensity of a laser to illuminate the phosphor, especially if the surface is moving. Thermometric resolutions of 0.1 C are obtainable, and some laboratory versions of these systems have been calibrated against NIST standards to even higher precision. To improve the measurement signal-to-noise ratio, synchronous detection timing has been used to repeatedly interrogate the same blade in a high speed rotating turbine. High spatial resolution can be obtained by tightly focusing the interrogation beam in measurements of static surfaces, and by precise differential timing of the laser pulses on rotating surfaces. We report here the use of blue light emitting diodes (LEDs) as an illumination source for producing useable fluorescence from phosphors for temperature measurements. An LED can excite most of the same phosphors used to cover the temperature range from 8 to 1400 C. The advantages of using LEDs are obvious in terms of size, power requirements, space requirements and cost. There can also be advantages associated with very long operating lifetimes, wide range of available colors, and their broader emission bandwidths as compared to laser diodes. Temperature may be inferred either from phase or time-decay determinations.

Cavity ringdown spectroscopy (CRDS) is one way of measuring small fractional absorption for concentrations down to sub- ppm levels in an optical cavity. The applicability of CRDS for measurement of diesel exhaust is assessed. By use of CRDS, instantaneous exhaust characteristics can be immediately available for engine control. Of specific interest in this set of experiments are measurements of soot or particulate matter. The goal of these measurement would be to estimate the number density of soot particles based on line-of-sight absorption and an assumption regarding the size distribution of the particles. To test the system, the absorption coefficients of Nitrogen, Carbon Dioxide, and 2',7'-Dichlorofluorescein in a test cell at known number densities were measured instead of diesel exhaust. An Nd:YAG-laser provided light at 532 nm for the cavity ringdown measurement. Cavity ringdown waveforms were analyzed with an exponential least squares fit. An equation relating the absorption coefficients to the ringdown time in a test cell was developed including the two parallel windows in the optical cavity. This analysis is based on the assumption that the measured output of the cavity decays exponentially according to a first order expression and the Beer-Lambert law. In the case of nitrogen, the measurement result were in good agreement unit, typically used for diesel exhaust soot measurement.

The analysis of detonator-timing performance has involved the use of rotating-mirror cameras (RMC) used in the streak mode and high-speed film. Fiducial timing marks are applied to the film to provide temporal references. The use of a RMC for detonator analysis requires aligning the camera, performing an exposure test, capturing light from the detonation and then processing the film. This procedure can take up to an hour for two technicians. After the film is possessed another technician compares each light streak on the film with the fiducial timing marks also recorded on the film. Capturing light from a detonator and recording it directly to a digitizer can improve detonator-timing measurement in several ways. The digitized signals can then be directly analyzed with software. The direct recording method reduces the need for expensive rotating mirror cameras, film processing and subjective optical measurement comparison. Furthermore, an extensive support facility requiring several specialized technicians is reduced to a single technician in a modest laboratory. This technician is then capable of performing several tests an hour. Tests were preformed to measure light intensity at detonation. An optical method of capturing the light was designed using a remote microscope coupled to optical fiber to bring the light to an optical/electrical converter and a digitizer then records the signal. This system is presently used in parallel with a RMC. The results are compared for accuracy.

This investigation focuses on the utility of rainbow schlieren as a tool to measure the temperature of axisymmetric partially premixed flames (PPFs). Methane-air PPFs are established on a coannular burner. Schlieren images are found to clearly visualize these PPF characteristics through light deflection by the steep refractive index gradients in the two reaction zone fronts. The temperature distributions of two flames established at overall equivalence ratios of Φ_r = 1.5, and 2.0, respectively; with Φ_l = 0 and the bulk-averaged velocities V_reac = 60 cm s^-1 and V_air = cm s^-1 are inferred from color schlieren images and an error analysis is performed. The errors arise due to two sources. One lines in the process of inferring the temperature for a refractive index measurement by making assumptions regrading the local composition of the flame. Another source involves the local uncertainty in the measurement of the transverse ray displacement at the filter plane that is used to determine the refractive index and, thereafter, the final temperature. The two errors combined lead to an uncertainty of less than 7 percent for both flames.

Optical diagnostic techniques can complement existing performance characterization methods for microthrusters under development for microsatellite technology. We present a design for a miniature nonintrusive optical diagnostic sensor to measure the flow characteristics of water-based microthrusters. Our design uses silica waveguide-based integrated optic sensors, which can be constructed as an integral part of microthruster walls, providing real-time, in-situ measurements, during tests and in flight. Based on available thruster characteristics and performance estimates supplied by the Air Force Research Laboratory at Edwards Air Force Base, together with calculations of the scattering and obscuration properties of the exhaust particles with plausible sizes and concentrations, we analyze acceptable sensor geometries, and examine feasible ranges of operation.

A novel laser Doppler technique is presented to measure flow fields with micro-scale resolution. The realized laser Doppler sensor provides distributed velocity measurements inside a defined measurement volume. Two laser wavelengths are used to accomplish two Doppler frequency measurements, which determine the position and the velocity of a scattering particle. Repeating of these measurements determines the velocity gradient of the flow. One application area is the evaluation of the velocity variations in boundary layers of flows close to a wall. This contribution presents the principle and experimental results of the spatially resolving laser Doppler velocity sensor. Different concepts on the optical arrangements as well as the signal processing technique are discussed. A scheme for the construction of a miniaturized fiber-coupled sensor is presented, which allows its integration into flow channels.

In this paper, an all fibre compatible laser Doppler velocimeter featuring a fibre-optic filter device for frequency discrimination is presented for the first time. The technique is based on the fabrication of a Fabry-Perot filter using in-fibre Bragg gratings for measurement of the in-line velocity component. The choice, design and fabrication of the in-fibre filters are discussed. Problems that affect the stability of the system are addressed. These include the design and implementation of two-independent active feedback control loops for the argon-ion laser wavelength and phase of the fiber-optic filter. An optical fibre-linked probe head, constructed in-house, is used to couple the laser beam at 514.5 nm to and from the measurement volume. Fast photomultiplier tube detectors are used and signal capture and processing is performed on a digital storage oscilloscope (300 MHz) or on a PC. The system is successfully demonstrated by measuring the velocity of a rotating disc (10-cm diameter) over a velocity range of +/- 15 ms^-1 with a resolution of 0.2 ms^-1.

In the conventional measurement of strain, resistance wire types of strain gauges have been used in most of cases. However, other kinds of strain gauges have been reported recently and optical fiber gauges appeared on the market. Here, instead of a conventional strain gauge made of a metal wire, we propose an optical fiber gauge. This gauge consists of two fibers for transmitting a beam from a light source and for receiving a reflecting-back beam, and in between them a concave mirror with a hole is settled. This mirror is used for transmission and partial reflection of the beam. When strain is given to the testing specimen to which the gauge is adhered, small displacement between two fiber ends is brought. The construction of this gauge is so sensitive to gap change between the fibers that high sensitivity is realized in measurement. In addition to high sensitivity, this gauge is featured by a small size and short gauge length. To verify this principle, experiments are repeated by using a thin plate specimen made of copper. The gauge is made of a plastic fiber of 0.5 mm in diameter and a small concave miro with a pinhole. Due to this mirror construction, the fluctuation of the beam intensity can be checked and the stable normalized output signal is obtained. Because the normalized signal is obtained form two signals; transmitted and reflected signals. An experimental result showed a high sensitivity in experimental measurement, and even for the intentional fluctuation of the beam intensity, we could get same measuring result in strain measurement.

Projection Moire Interferometry (PMI) has been used to measure the structural deformation of micro air vehicle (MAV) wings during a series of wind tunnel tests. The MAV wings had a highly flexible wing structure, generically reminiscent of a bat's wing, which resulted in significant changes in wing shape as a function of MAV angle-of-attack and simulated flight speed. This flow-adaptable wing deformation is thought to provide enhanced vehicle stability and wind gust alleviation compared to rigid wing designs. Investigation of the potential aerodynamic benefits of a flexible MAV wing required measurement of the wing shape under aerodynamic loads. PMI was used to quantify the aerodynamically induced changes in wing shape for three MAV wings having different structural designs and stiffness characteristics. This paper describes the PMI technique, its application to MAV testing, and presents a portion of the PMI data acquired for the three different MAV wings tested.

In this paper, a phase shifting technique for atomic force microscope (AFM) scanning moire method is proposed. The phase shifting is realized in four steps from 0 to 2π by a piezo-scanner in AFM. The measurement method and experimental techniques are described in detail. For demonstration, this method is applied to determine the phase distribution in AFM moire of a 1200 lines/mm holographic grating used to measure thermal deformation in a QFP electronic package.

In this paper, a Dynamic Digital Speckle Interferometry (DDSI) applied to optical diagnosis of gas-liquid phase change is proposed. The basic principle and experimental system of the DDSI are presented. This technology of flow optical diagnosis has the following three main advantages. First, DDSI uses a CCD camera as record device of a specklegram and a microcomputer, which processes the specklegrams to obtain a speckle interferogram. Therefore, the DDSI does not need the photographic film and optical dark room that usually are needed for holographic interferometry and speckle photography. Second, in DDSI technique, the information of density field in flow is obtained by using a double exposure with and without flow variation respectively. As a result, it can automatically eliminate the effect of the density nonuniformity of the optical windows of test section on the density measurement (like holographic interferometry). Third, the DDSI can be used for dynamic visualization and real time measurement of continuous variation of density with time in flow (like M-Z interferometry). The gas-liquid phase change process of freon R13 is investigated experimentally. By means of the DDSI technique, both density distributions in gas phase and liquid phase of R13, which are located on two sides of gas-liquid interface respectively, can be measured when gas-liquid phase change occurs. It is also observed that the interface between gas-phase and liquid-phase has a thickness of the order of hundreds micrometers, when the temperature of R13 flow comes close to its critical temperature. The variation laws of the interface thickness with the temperature of R13 are discussed. The interface behaviors of movement, disappearance and renewal are presented. The investigations show that DDSI is very suitable for the optical diagnosis of gas-liquid phase change in mini or micro scale. It provides an effective method for experimental investigations on heat transfer and flow in mini or micro scale.

A videogrammetric technique developed at NASA Langley Research Center has been used at five NASA facilities at the Langley and Ames Research Centers for deformation measurements on a number of sting mounted and semispan models. These include high-speed research and transport models tested over a wide range of aerodynamic conditions including subsonic, transonic, and supersonic regimes. The technique, based on digital photogrammetry, has been used to measure model attitude, deformation, and sting bending. In addition, the technique has been used to study model injection rate effects and to calibrate and validate methods for predicting static aeroelastic deformations of wind tunnel models. An effort is currently underway to develop an intelligent videogrammetric measurement system that will be both useful and usable in large production wind tunnels while providing accurate data in a robust and timely manner. Designed to encode a higher degree of knowledge through computer vision, the system features advanced pattern recognition techniques to improve automated location and identification of targets placed on the wind tunnel model to be used for aerodynamic measurements such as attitude and deformation. This paper will describe the development and strategy of the new intelligent system that was used in a recent test at a large transonic wind tunnel.

This paper reports an experiment that demonstrated the functionality of a commercial heterodyne interferometer with an oblique-angle fold mirror in the laser feed path. The key issue investigated is whether the oblique angle fold mirrors introduce unacceptable levels of polarization mixing. The manufacture's specifications recommend that only orthogonal fold mirrors be used to control polarization mixing. However, this constraint limits the use of the interferometer for applications such as the measurement of structural dynamics. In the experiment, an orthogonally-fed interferometer was compared to an oblique angle interferometer at roughly 45°. The result indicated a linear relationship between the two measurements to within 0.5 percent. As a result, no evidence of the λ/2 wavelength sinusoidal bias characteristic of polarization mixing errors was found. A 9 percent error did however exist between the intended and observed scaling between the two measurements. While hardware alignment errors are a likely cause of this disagreement, a third axis of measurement is recommended for future investigations.

Shearography is a full-field optical technique usually used for the determination of surface strain. Correlation of interferometric speckle patterns recorded before and after the object deformation yields fringes sensitive to displacement gradient, from which the surface strain can be calculated. A full analysis of the surface strain requires the measurement of six displacement gradient components, using three illumination directions and two directions of applied shear. Additionally shearography may be used to measure surface slope by correlation of interferograms obtained before and after a source displacement to yield fringes sensitive to surface slope. Integration of the slope yields the object shape. In this paper shearography is used to measure the six components of displacement gradient of a gas main pipe under pressure, the surface slope of the pipe and the shape of the pipe. The object slope and shape are used to correct the displacement gradient measurements for variation in sensitivity vector across the object surface and for sensitivity variations due to the dependence of the applied shear upon the local slope of the object surface. A coordinate transformation, incorporating the object shape information, is used to obtain the in-plane and out-of-plane displacement gradients relative to the local profile of the surface.

The INEEL has developed a photorefractive ultrasonic imaging technology that records both phase and amplitude of ultrasonic waves on the surface of solids. Phase locked dynamic holography provides full field images of these waves scattered from subsurface defects in solids, and these data are compared with theoretical predictions. Laser light reflected by a vibrating surface is imaged into a photorefractive material where it is mixed in a heterodyne technique with a reference wave. This demodulates the data and provides an image of the ultrasonic waves in either 2 wave or 4 wave mixing mode. These data images are recorded at video frame rates and show phase locked traveling or resonant acoustic waves. This technique can be used over a broad range of ultrasonic frequencies. Acoustic frequencies from 2 kHz to 10 MHz have been imaged, and a point measuring (non-imaging) version of the system has measured picometer amplitudes at 1 Ghz.

Many paper mills use ultrasonic techniques to measure the Tensile Stiffness Index, TSI, of the paper sheet. They then assume that the TSI value is the same as the fibre orientation anisotropy. This is true if the paper is allowed to dry without any internal tension or elongation, but does not apply to paper manufactured in a paper machine. The paper machine introduces tension and elongation as soon as the fibre is placed on the forming fabric. These factors increase through the press section and are accentuated in the drying section. In order to uniquely measure the fibre orientation anisotropy on the surfaces, the proposed method uses replicas of both paper surfaces to produce a laser diffraction pattern. The obtained pattern reveals an elliptical shape, which is related to the fibre orientation anisotropy of the paper surface. By measuring the ellipticity of the diffraction pattern and the deviation with respect to the machine direction, one can quantify the fibre orientation distribution. Different papers from the bench market have been successfully tested with the developed system. This article describes the new developed optical system and its innovative capabilities in the field to produce maps of the fibre orientation of a complete paper sheet surface. A selection of the obtained results to prove its feasibility is also presented.

Spectrally Resolved White Light Interferometry (SRWLI) is used for precise measurements of both the sample width and the differential refractive index, attaining precision of about 10^-6 in the refractive index. This is achieved through the experimental simulation of a thin virtual cell about 40μm wide.

We present a method of 3-D profile measurement to obtain the xyz-coordinates of complex surfaces based on multipoint diffraction interferometry. This method uses multiple sets of diffraction light sources, each of which is made of two single-mode optical fibers emitting spherical wavefronts. Fringe patterns generated by the interference of two spherical wavefronts are illuminated on the target surface, whose phases are precisely determined by using phase-shifting technique. Finally, measured phase information is directly related to the xyz-coordinates of the target surface utilizing principles of multilateration.

Development of an aero-optics simulation code is reviewed. When completed, the code will contain three elements, 1) an algorithm for producing physically plausible aero-optical properties and bounds on properties characterizing flows of interest, 2) an algorithm for converting these into aero-optical features of a flow described by a set of time varying, random, phase masks, and 3) a code that will integrate these and propagate a wavefront through a typical test scenario with an output similar to that provided by the test diagnostics. The resultant aero-optics computational simulator will allow an aerodynamicist to simulate and run aero-optical tests that will be useful for test planning and data interpretation. This paper reviews the approach taken by the author in modeling aero-optic phenomena and presents initial results based on a simplified model of a turbulent condition through which point source wavefront is propagated.

Stereoscopic tracking velocimetry (STV) can be a very efficient diagnostics tool for detecting three-dimensional three-component flows with great experimental freedom and computational processing speed but for a restricted region. To achieve the goal of near-real-time measurement with reasonable measurement accuracy, a particle tracking algorithm has been developed, which is an essential part of STV. The developed particle tracking is based on an optimization approach, hence it is a good candidate to be solved by applying computational neural networks. In this paper, we present the new tracking algorithm and its measurement applications to the material processing involving directional solidification as well as to a pulsating free-jet flow. Preliminary comparison of experimental and numerical results is also presented. We believe that by utilizing the massive parallel-processing power of neural networks for optimization, reliable solutions in the STV application can be obtained for near-real-time data extraction and display.

Artificial neural networks have been used for a number of years to process holography-generated characteristic patterns of vibrating structures. This technology depends critically on the selection and the conditioning of the training sets. A scaling operation called folding is discussed for conditioning training sets optimally for training feed-forward neural networks to process characteristic fringe patterns. Folding allows feed-forward nets to be trained easily to detect damage-induced vibration-displacement-distribution changes as small as 10 nanometers. A specific application to aerospace of neural-net processing of characteristic patterns is presented to motivate the conditioning and optimization effort.

This study aims at estimating a moving heat source with a 3D inverse model and a high spatial resolution. In order to cope with the large amount of computations required in the 3D case, a linear unsteady inverse model based on the principle of superposition has been made. Two concepts are used to reduce the computational time: the first one is linked to ht diffusion time of the eta and the second one is linked to the redundancy of the information. Firstly, numerical test are presented. The, a laboratory experimentation consisted in the estimation of the flux of a moving laser beam is described.

Solid State array sensors are ubiquitous nowadays for obtaining gross field images in numerous scientific and engineering applications including optical diagnostics and instrumentation. Linear responses of these sensors are often required as in interferometry, light scattering and attenuation measurements, and photometry. In most applications, the linearity is usually taken to be granted without thorough quantitative assessment or correction through calibration. Upper-grade CCD cameras of high price may offer better linearity: however, they also require linearity checking and correction if necessary. Intermediate- or low-grade CCD cameras are likely to need calibration for achieving linearity. Here, we present two very simple approaches: one for quickly checking camera linearity without any additional setup and the other for precisely correcting nonlinear sensor responses. It is believed that after calibration, those sensors of intermediate or low grade can function as effectively as their expensive counterparts.

This paper presents a new achievement in PIV image processing research. A new image processing software system of particle tracking velocimetry has been developed. This system is based on a series of unique image processing and patterns recognition algorithms, including image enhancement, particle identification, and particle matching. It has been evaluated with several standard PIV images constructed by The Visualization Society of Japan (VSJ). With the post processing function of the software, some other kinds of flow field characteristics could be described. Finally, this software has also been tried in practical PIV flow field measurements. This work is about the internal flow measurement of transonic compressor, conducted on the transonic compressor rig of National Air-engine Thermal Dynamic Key Laboratory, Beijing University of Aeronautics and Astronautics, China. The result of the PIV image processing was compared with that obtained with the correlation algorithm software. The comparison result has proven to be quite agreeable and even more efficient.

Moire interferometry is a powerful technique for high sensitivity in-plane deformation contouring. However, from an engineering viewpoint, the derivatives of displacement, i.e. strain, is the desired parameter. Thus there is a need to differentiate the displacement field. Optical and digital methods have been proposed for this differentiation. Optical methods provide contours which still need to be quantified, while digital methods suffer from drawbacks inherent in the digital differentiation process. In this letter we describe a novel approach of strain segmentation the moire pattern using a multi-channel Gabor filter. Appropriate filter design allows for user-specific segmentation, which is essentially in engineering design and analysis.

A single-camera Planar Doppler velocimetry system has been demonstrated, in which illumination beams at two closely-spaced optical frequencies are derived from a single Argon-ion laser. The frequency of one beam lies on an absorption line of iodine vapour, and the other just off the absorption line. The beams sequentially illuminate a plane within a seeded flow and the Doppler-shifted scattered light passes through an iodine cell onto a single solid-state camera. Light scattered from the measurement plane from the beam with its wavelength set to be off the absorption line is not affected by its passage through the cell, and provides a reference image, while that from the beam on the absorption line encodes the velocity information as a variation in transmission dependent upon the Doppler shift. The complex imaging system required for conventional PDV is eliminated, since superposition of the reference and signal images is automatic. The two beams are generated by an optical arrangement incorporating an acousto-optic modulator, and are transmitted to the region of interest by a single mode optical fibre, which ensures both a smooth Gaussian illumination profile and co-linearity of the beams. The system is demonstrated using a spinning disc and a velocity resolution of +/-1 ms^-1 is achieved.

This paper describes a planar Doppler velocimetry (PDV) technique that is capable of measuring the three, instantaneous components of velocity in two dimensions using a single pair of signal and reference cameras. PDV can be used to measure the instantaneous 3-D velocity of a fluid by using an absorption line filter (ALF) to determine the Doppler shifted frequency of a narrow line pulsed laser (Nd:YAG) that has been scattered off particles seeded into the flow. In the technique presented here the three views required to obtain three dimensional velocity information are ported from the collection optics to a single imaging plane using flexible fiber imaging bundles. These are made up of a coherent array of single fibers and are combined at one end as the input plane to the measurement head. A fourth leg of the imaging bundle is used to image the individual laser pulses and allow correction for pulse-to-pulse frequency variations. The results reported in the paper are from the development phase of the system and are of the velocity field of a rotating wheel.

The measurement of the concentration distribution is always important in industry. Many researches on image reconstruction of the two phase-flow field have been made in recent years. Various methods have been used such as capacity CT, resistance CT, x-ray CT and so on. When the flow has low concentration, however, measurement accuracy of these methods is poor. In addition, it needs the measurement to be free of charge in some case. In this paper, we have a pilot study for the two-phase flow utilizing the optical fiber sensors. Two turbidity samples with different attenuation have been used to simulate the cross section distribution of the two-component flow. The graded-index fiber lens in the end of the optical fiber has been used in order to improve the coupling efficient and decrease the cross talk of the adjacent channel s. Finally, we make use of the linear back projection arithmetic (LBP) to reconstruct the image of the sample. A filtering method has been used to eliminate the star noise owing to the LBP arithmetic. We find that the reconstructed images are very well consistent with the cross-section distribution of the samples.

Laser speckle photography is a well-established optical method for quantitative measurements in solid and fluid flow with wide dynamic range. In conventional technique of this method, an analogue processing based on auto-correlation evaluation has been applied to reconstruct deformation, velocity or density gradient by using optical Fourier transformation of a double-exposed laser speckle pattern recorded on a photographic film. This technique can be improved in the spatial resolution, in the dynamic range and in the efficiency of image processing by applying the digital cross-correlation evaluation between the reference and the object speckle patterns, which are separately recorded. It is called digital laser speckle photography. In practical procedure of this method, both of the reference and the object speckle pattern are recorded by using a digital still camera or CCD camera. The same algorithm with cross-correlation evaluation in PIV is applied to reconstruct the distribution of the displacement of local speckle patter from the digital images of speckle patterns. The accuracy and the dynamic range in practical measurements can be evaluated for practical devices used and experimental conditions. This method is applied to density field measurements of thermal convection constrained acoustically in a horizontal duct, and the effect of sound field on thermal convection is discussed.

Holography has been used in several past space missions. One popular experimental mode deals with the study of fluid refractive properties in a crystal growth cell. The perceived advantage of holography is that it stores the reconstructed wavefronts so that complete information is available later on the ground. That means the wavefront can be analyzed not only by traditional holographic interferometry but by other means as well. We successfully demonstrate two such methods described here. One is deflectometry using a Ronchi grating and the other confocal optical processing. These results, using holograms from the Spacelab-III mission dealing with triglycine sulfate crystal growth clearly demonstrate that a single data collection system can perform the task of several fluid experimental systems. Finally, the possibility of using reconstructed wavefronts with other analysis modes like speckle techniques and video holography are discussed. The present study firmly establishes the advantages of holography.

No abstract available.

The paper presents some research works conducted in National Key Laboratory of Aircraft Engine of China on the shock containing supersonic flow measurement as well as the internal flow measurement of transoijc compressor by PIC technique. A kind of oil particles in diameter about 0.3 micrometers containing in the flow was discovered to be a very good seed for the PIV measurement of supersonic jet flow. The PIV measurement in over-expanded supersonic free jet and in the flow over wages show a very clear shock wave structure. In the PIV internal flow measurement of transonic compressor a kind of liquid particle of glycol was successful to be used as the seed. An illumination periscope with sheet forming optics was designed and manufactured, it leaded the laser shot generated from an integrate dual- cavity Nd:YAG laser of TSI PIV results of internal flow of an advanced low aspect ratio transonic compressor were shown and discussed briefly.

Two phase flows widely exists in many industrial system, much attention has been directed to the use of process tomography in determining the concentration profile in the fluid conveying pipe. This paper preliminarily studies the application of optical tomography in gas-solid two phase flow parameter measurements. We obtain different optical signal as the variation of mass concentration, by means of the variation of diameter of funnel. We find the linear relation between the mass concentration of solid particle and extinctivity, which is consistent with theoretical analysis. In addition, experiments verified that the extinctivity in different position in the direction of light propagation is unconverted, which meets the working conditions of backprojection reconstruction. According to the principles of computer tomography, we obtain the projections of measured 2-D cross section in multi-angle, and read gray scale data of every image element, then the reconstructed image is yielded by backprojection routine. The gray value of each image element corresponds to the mass concentration of the physical position. By means of experiments, we can make a conclusion that it is feasible to obtain the concentration distribution of cross-section by use of optical tomography for measurement.

In this paper, a DPIV system was used in which the CCD camera was so called frame straddling camera and the cross- correlation method was used for the particle image processing. For flow velocity uniformity measurements a special Pre-bias method was provided and in principle the measuring accuracy of the new method could increase to one order level. It makes the possibility to measure the uniformity of the flow velocity fields using PIV.

The property of crystal depends seriously on the solution concentration distribution near the growth surface of a crystal. However, the concentration distributions are affected by the diffusion and convection of the solution. In the present experiment, the two methods of optical measurement are used to obtained velocity field and concentration field of NaClO₃ solution. The convection patterns in sodium chlorate (NaClO₃) crystal growth are measured by Digital Particle image Velocimetry (DPIV) technology. The 2-dimentional velocity distributions in the solution of NaClO3 are obtained from experiments. And concentration field are obtained by a Mach-Zehnder interferometer with a phase shift servo system. Interference patterns were recorded directly by a computer via a CCD camera. The evolution of velocity field and concentration field from dissolution to crystallization are visualized clearly. The structures of velocity fields were compared with that of concentration field.

An optical diagnostic system consisting of the Mach-Zehnder interferometer with the phase shift device and the image processor has been developed for the study of the kinetics of protein crystal growing process. The concentration capillary convection around growing protein crystal was investigated during the process of trichosanthin crystal growth. The observation in real time showed that the concentration capillary convection associated with the surface tension of the crystallizing solution occurs at the vicinity of the surface of the protein mother liquor and directly affects on the outcome of protein crystallization, including the process of growth and the quality of resulting crystal. So far the detailed analysis and the important role of the concentration capillary convection in protein crystallization has been overlooked in both the space- and the ground-based crystal growth experiments. This may be one of the reasons for the majority of the results of space-based investigation shown no improvement.

The paper deals with the theory of measurement of an object in-plane velocity (object as a rigid body) by means of the method availing the statistical properties of the speckle field (speckle pattern). At first, the general theory of determination of the small deformation tensor of an elementary area of an object surface using the electronic speckle correlation in the optically free space and in the image field is briefly mentioned. Furthermore, the philosophy of measurement and interpretation of measurement is presented and the analysis of sensitivity and accuracy is also shortly done.

It is developed a new approach to the study interferometric pictures properties at flow visualization. Interferometric fringes are defined as family of solutions a differential equation, which establishes slope of the fringes as function of light refraction vector components and of initial tuning two beam interferometer parameters. The approach allows both to systematize knowledge about pictures and to make prediction they behavior depend on properties to be investigated density flow field and initial tuning parameters. On base the qualitative theory differential equation it is realized possibility to study symmetry, smoothness of fringe, singularity points of the pictures. Early some of the proposed ideas were used for statement models of 2D-density flow field under analysis experimental interferometric pictures to reduce duration of the data processing. It is assumed an application for the choice 3D density field models under the same analysis in complex flow to be investigated with aid of digital interferometry. Such flows take place at diffraction of shock waves. The singularities are illustrated by means of interferometric picture examples, which was visualized under experimental study 2D and 3D gas flows.

Mechanoluminescence (ML) materials are known to emit light due to the application of mechanical stress. The ML responding to elastic deformation, plastic deformation and fracture is referred here as elasoticoluminescence, plasticoluminescence and fractoluminescence, the former two belong to non-destructive ML and the later belongs to destructive ML. Until now, the destructive ML has been observed in various inorganic and organic materials, whereas the non-destructive ML has been found in very limited cases. No practice application of non-destructive ML has been realized so far. On the other hand, ML material as it transfers a mechanical stress into a light emission, is believed to be a new smart material for various mechano- optical applications. Recently we have done a series research on ML both in fundamental and application aspects. This paper focuses on the investigation of elastico- luminescence. The results of the present work reveal that the ML coatings on the surface of solid can direct display the stress distribution by a mechanolumnescnce image.

A continuous effort has been undertaken at ONERA over more than 30 years to develop non intrusive methods to characterize various kinds of flows: subsonic to supersonic aerodynamic flows, combustion and reactive flows, hypersonic flows. The paper is giving an overview of the methods dedicated to measure the velocity; they are mainly particle scattering based for aerodynamic flows (such as LDV, PIV or DGV), but for reacting and hypersonic flows the molecular scattering based methods avoid the particle lag problem (such as CARS velocimetry, diode laser absorption spectroscopy or electron beam fluorescence).

The state of the art in Rainbow Thermometry is presented. Rainbow Thermometry is a technique for measuring size and temperature of transparent droplets. For data inversion a rainbow pattern is employed, which is formed by a single droplet or by constructive interference of laser light scattered by an ensemble of spherical droplets. In the first case, one speaks about Standard Rainbow Thermometry (SRT), investigated since 1988. In the second case, the technique is called Global Rainbow Thermometry (GRT), studied since 1999; here, the non-spherical droplets and liquid ligaments results in a uniform background and thus do not influence the interference pattern, formed by the spherical droplets, from which average size and temperature are derived. This is a large improvement with respect to Standard Rainbow Thermometry, which is strongly influenced by particle shape. Moreover, GRT is applicable for smaller droplets than the standard technique because the global pattern is not spoiled by a ripple structure. Data inversion schemes based on inflection points, minima and maxima are discussed for SRT and GRT. The standard technique is applied to a monodisperse burning droplet stream, where the problems with particle shape do not exist. Global Rainbow Thermometry is applied to a heated water spray, where the standard technique fails. For both applications the accuracy in the temperature measurement was a few degrees Celsius.