The force which such a model as a cylinder or a square cylinder receives from an uniform flow is well known to be reduced by the small objects arranged in the upstream side of the model. In this study, the effect of the number of the small objects, their arrangement and their shapes on the flow around a cylinder is examined using a flow visualization. The location of vortex in the downstream side of a cylinder and Strauhal number of vortex releasing are examined using the obtained images in this study. And, the location of the vortex is also examined in the case of the plate arranged in the downstream side of a cylinder.
Usually, steady pipe flow is luminar Reynolds number Reis less than 2320, and turbulent when Reis more than 3000. However transition Reynolds number in the acceleration pipe flow is much bigger than that of steady flow, where the transition is only judged by the velocity fluctuation. Transition to turbulent in acceleration flow has not been proved by flow visualization. In this paper flow visualization was conducted to prove the transition in accelaration pipe flow. The relation between acceleration and transition Reynolds number was almost the same as that by Lefebvre.
This paper describes the classification of pulsating jets. The flow fields and the motions of vortices characterizing the pulsating jets were experimentally examined using both the smoke visualization method and the velocity measurement. The results of the velocity variation are found to agree with those of the flow visualization. The pulsating jets can be classified into three kinds of flow state; they are termed a row of puffs, a row of vortex rings in jet column mode, and a row of vortex rings in shear layer mode. In this paper, we defined the "puff" as a lump of fluid consisting of a leading vortex and a trailing jet following the vortex. The puff may be regarded as the state possessing the most fundamental features of a pulsating jet. Each run corresponds to a point on a 2-D regime diagram, where the governing parameters are chosen as the coordinate variables. The plotted result of the points indicates that the choice of the parameters is adequate to classify the flow states.
Authors found that in a flow through two intersecting ducts with a 60°intersecting angle, two uneven inlet flow streams may result in an equalization of two downstream exit flows after their collision in the intersecting section and a subsequent formation of vortices in the downstream ducts. It is important to investigate the relation between flows and vortices in intersecting ducts as a basic study. In this paper, an experimental study was conducted to investigate flow characteristics in two intersecting ducts with an extra cavity. Flow visualization by means of a tracer method determined flow patterns, and pressure drop measurements using a piezometer were conducted. It is concluded that flow characteristics included a suction effect in the extra cavity of intersecting ducts are determined by the interaction between vortices and main streams.
A pair of wave packets of oblique T-S waves around an isolated turbulent spot, which was produced in the laminar region of a radial liquid film flow, was investigated. The liquid film flow was formed by a water discharge to the atmosphere from a thin cylindrical gap between the end of a vertical pipe and the surface of a horizontally placed flat disk. The turbulent spot was created by a pulse-like jet injection into the laminar region through a small hole of the disk, observed by high-speed photography. Furthermore, the evolution of a pulse-like disturbance, which was added to the mean flow, was analyzed by the finite difference method with VOF method. It was found that the wave packets were generated by the pulse-like disturbance introduced to the laminar flow at the moment of the jet injection.
The author et al. made glass cylinder engine in which closed gap of piston ring could be visualized based on the idea that follow-up characteristic of piston ring to the sliding surface of bore in internal combustion engine, could be evaluated from minute change of closed gap of piston ring. This newly-devised visualized engine was an in-line 4-cylinder engine, capable of running up to 6000 rpm, in which we could observe closed gap of piston ring minutely during operation. As the result of the evaluation of the follow-up characteristic of piston ring with this equipment, it was found that going-up passage of oil was widened and so, oil consumption increased, because abnormal behavior, that is, the separation of piston ring from deformed bore sliding surface at the time of goingdown of piston, happened in high speed area.
Free jet diffusion flame photographs were taken by high-speed video camera. Propane was used as fuel. Flame images are digitized into 24-bit full color images by using commercial software. The digital color image is decomposed into 8-bit images of the Red, Green and Blue components and moreover each component is converted into decimal ASCII data by means of our program. In this study, the Red component luminosity fluctuation is investigated for five different fuel exit velocities. The ASCII data of 3000 frames are stored into Microsoft Excel and the time-averaged value and fluctuation intensity of luminosity are calculated by our program based on the Visual Basic Applications Edition (VBA) in Excel. These results are recomposed into 8-bit BMP images and visualized as the density slicing pseudo color images.
Liquid accelerants including kerosene, motor gasoline, and diesel fuel are often encountered in arson cases. The investigator must discover the presence of accelerants at the fire scene. Methods for their detection have been a subject of forensic interest. Visualization of a liquid accelerant at the fire scene was studied. Excitation and fluorescence spectra of liquid accelerants were measured. Broad fluorescence band in the spectral range between ultraviolet and shorter-wavelength region of visable were obtained when the excitation was performed in the ultraviolet spectral range. It is difficult to detect these fluorescenece by human eyes. An image intensified CCD camera was used to visualize the fluorescence of accelerants. The experimental results show the applicability of new method to detection of liquid accelerants at the fire scene.
In this study, time-lapse monitoring data of ground improvement at the foundation site of the fuel tank has been analyzed using resistivity tomography method in order to apply it for field data interpretation. And then, the simple model simulation has been performed for the purpose of improvement of resistivity measurement data analysis and evaluation. Firstly, it has been studied to use both data measured by electrode arrays (Wenner and Eltran) that have the different property of exploration each other into inversion process as a method to acquire the model with high reliability from a few data. And, as the result of the resisitivity division analysis it is conceivable that we can remove noise from field data by calculating noise model previously.
Gas jets injected into atmosphere through round nozzle were visualized by Schlieren method and pictures were taken by digital camera. The new method of analysis using fractal dimension that represents the complexity of the form of the object is established, and fractal dimension is calculated from luminance of jet images, and a structure analysis is done.
Flow field in the gap space between two circular cylinders forming a cross was visualized under the Reynolds number of about 1200 by using a method of dye injection. As the results, the various patterns of necklace vortex system are produced, depending on the gap space, G, between two cylinders. In the case of G/d=0, the boundary layer on the surface of the upstream cylinder separates and rolls up as a main necklace vortex near the symmetrical plane. In the case of G/d=0.3, the necklace vortex system consisting of four vortices is formed, and surrounds the downstream cylinder.
An experimental study was carried out to elucidate the flow characteristics around the louvered fins used in a radiator and condensor for motorcars. The flow velocity and pressure distribution around an inclined forward facing step, imagined as a louvered fin, were measured in a duct as a parameter the flow rate in downstream of the step. Flows around the inclined forward facing steps of the two kinds of 90° and 30° were examined using the fiberoptic Laser Doppler Velocimeter(FLDV) and flow visualizing method by dye injection. The flow which goes over the step forms a recirculating zone just behind the step due to flow separation. The flow through the opening part just near the step is passably obstructed by a slow-moving vortex occuring in the opening part. The reattachment point length of the step which the opening part is closed, is obtained from flow velocity measured by FLDV.
The flows in the wake of a flat plate in a uniform shear flow were visualized by hydrogen bubble technique. The generator of the shear flow was made according to the method by Kotansky. Velocity distributions in the shear flow generated were measured. The behaviors of vortex street behind a flat plate at various angles of attack were observed. The relation between the flow patterns and the structure is discussed.
We have been researched on the velocity field measurements of gas-liquid interface EHD flow phenomenon. This is the unique phenomenon of which the flow of the electrically-charged fluid behavior is induced inside the liquid, when corona discharge is caused for the gas-liquid interface. Generally, EHD wind called the ion wind blows, when corona discharge is generated in the gas phase. Then, the flow field which resembled flow phenomenon done the inducement under gas phase corona discharge very well was able to be observed, when the wind which simulated the ion wind for this gas-liquid interface was blown. This paper describes PIV measurements of the wind induced flow in stratified liquid. The velocity fields of the wind induced flow are successfully obtained by means of the flow visualization technique and the PIV technique..
Short fibers in a concentrated fiber suspension are visualized in a high contrast with a suspending fluid. The concentrated fiber suspension becomes transparent by employing an optimal index-of-refraction match of fibers and suspending fluids. Moreover, vinylon fibers as tracers are added to the fiber suspension because vinylon fibers having birefrigence are clearly observed using a transmitted light under crossed nicols.
Interlaced-scan CCDs which are widely used for the capture of motion pictures, have same disadvantages such as interlinear time lag, decreasing of resolution caused by analog video output, etc. To overcome these disadvantages, Progressive-scan CCDs are developed, which have many advantages such as progressive scanning without interlinear time lag, square pixel, high resolution and high frame rate over interlaced-scan CCDs in measurement of moving objects. In order to make use of the progressive scanning CCD for many image recognition applications, it is important how high-speed transmitted digital data can be stored in real time. We developed a motion picture recording system specialized for the progressive-scan CCD camera to utilize advantageous progressive-scan CCD and this system is applied to capture images of Laser Scanning Visualization.
In this report, in order to evaluate influence of pad shape on the behaviour of Taylor vortices in submerged multi-pad journal bearings, fluid film flow in bearing clearance and fluid flow between pads were visualized experimentally. Critical Taylor number decreased with an increase of pad spacing irrespective of pad shape. Two-dimensional flow field between pads were measured by Particle Image Velocimetry. In the case of streamlined pads, fluid flow entered rear pad fluently.
We have developed a novel image measurement technique called paint erosion method (PEM) to estimate wall shear stress (WSS). In the PEM, the WSS is estimated from the paint erosion rate obtained by the instantaneous change of light transmission power on the image. In this study, we attempted to depict WSS distribution of the diaphragm-type pulsatile blood pump in our total artificial heart by the PEM, and further compared the obtained WSS distribution with in vivo thrombus deposition area. The average WSS contour map inside the blood pumps were successfully obtained by using the PEM, and in vivo thrombus deposition area coincided with the low WSS of less than 2.7 Pa. We concluded that WSS mapping based on the PEM provides useful information for predicting the preference area of in vivo thrombus formation in a pulsatile blood pump and facilitates improving its antithrombogenicity from the viewpoint of flow dynamics.
Experimental study has been conducted on flow structure and heat/mass transfer characteristics in the rectangular duct with a sharp 180-deg turn. Detailed distributions of local heat/mass transfer rates over the all duct walls and those of mean velocity have been measured using the naphthalene sublimation technique and PIV (Particle Image Velocimetry), respectively. The results show that the geometry-induced separation bubble is formed at immediately downstream of turn and the heat/mass transfer is low on the corresponding area. Also, the flow impingement on the upper stream parts of the end wall and of the outer wall after turn is the most important fluid dynamic factors that dominate the mass transfer distribution.
The flow and temperature visualization of thermal plumes from two-heat sources in a rectangular vessel was simultaneously performed by using liquid crystal suspensions. Two-heat sources (constant temperaure) were set with 50 mm pitch on the bottom surface. Side walls were insulated thermally. Scattered light from the liquid crystal suspensions was transformed by using regression equation of relative brightness. The two dimensional behavior of the flow and the temperature distribution on the cross section were obtained by illuminating vertically and horizontally. Two thermal plumes were generated and moved vertically. They were distorted to the center and combined each other. Two large recirculation flows were constructed between side walls and thermal plumes, Additionally, high temperature layer was generated near the upper wall.
The color of thermo-sensitive liquid crystal responds to the temperature change. This property is very useful for thermal field visualization. The temperature of visualized thermal field is analyzed with the relationship between temperature and color. Thermosensitive liquid crystal changes their color not only temperature but also observation angle. Therefore, the relationship between temperature and color each observation angle, can be applied in temperature measurement. Since temperature measurement range with a thereto-sensitive liquid crystal is narrow, in this study, we expand the range by using plural thermo-sensitive liquid crystals. We use the neural network for color-to-temperature caliblation. As a result, we suceed in temperature measurement with wide temperature range.
Measurements of heat distribution on the surface of acrylic block processed by an infrared laser have been made using an infrared thermography and an image analysis system. Thermal vectors due to laser irradiation can be derived from the temperature gradient of thermal images. Using the cross-correlation of the thermal vectors obtained in sequent two pictures, time variation of the thermal vectors has been derived which are referred to as "thermal change vectors". Because of the use of relatively low power on acrylic block, it is possible that the heat conductive phenomenon of the processing is observed through the heat radiation ranged from 3 to 5.4 μm which can be detected with the used thermography. This method examines the heat conductive phenomenon occurred in the acrylic surface processed by the laser to characterize the processing quality.
Flow and temperature patterns of natural convection in a thermosyphon with rectangular cross section were simulated numerically. Dimension of the thermosyphon model was 100mm height and 3Ox3Omm cross section. The model was placed vertically, and upper 1/3 zone of the total height was cooled, lower 1/3 zone was uniformly heated and middle zone was thermally insulated. Silicon oil was used as a working fluid. The steady natural convection flow appeared under a certain temperature condition. This paper describes numerical results of this flow in detail. In case of temperature difference ΔT=1K symmetrical flow and temperature patterns were displayed.
This paper is concerned with the new type of the cooling unit to which the flow mechanism of fluidics called "the vortex chamber oscillation device" is applied. The water jet issuing from this cooling device impinges on the heated plate with swinging by itself. Since the flow mechanism of swinging water jet and the impinging property have been reported already in previous paper, the cooling process by this cooling device have been visualized through the infrared camera in this paper. Furthermore, by comparing the cooling area by the swinging water jet with that by non-swinging one, the validity of this proposed cooling unit have been confirmed.
Temperature field and flow one caused by the heat source under a plate are visualized by liquid crystal partices. The pictures are analyzed by the cross-correlation method and by numerical calculation. It could confirm how a heat flow around the heat source develops by measuring the velocity due to the time progress. As the power input increases, thermal convection is promoted, and Nu and velocity increase. The phenomenon which doesn't get clear can be known by a numerical calculation.
The soil temperature distributions around underground heat exchange pipes were measured on typical models in order to check the results of numerical calculations.The performances of heat storage in the cases of several system were calculated numerically by using the finite difference method. Its variables include: thermal diffusivity of soil and pipe diameter. Calculated results were generalized by the relationship between the dimensionless heat flux and the dimensionless time which is defined by the pipe diameter. This diameter significantly affects the characteristics of heat storage. Consequently, the characteristics of heat storage were discussed in comparison with a straight pipe with infinite space. And the optimum diameter required for the arrangement of under ground pipes was obtained.
When the isothermal heated rib that was placed on lower plate of the horizontal paralleltwo plates is one piece or more than one, the flow pattern in the channel of two parallel plates, and the natural convection heat transfer coefficients of the surface of the ribs were experimentally studied. The flow pattern was visualized by inserting the tracer particle in equipment, and then inserting the slit light from the side of the equipment. The heat transfer coefficients of the surface of the ribs were decided from visualization of thermal field using the shadowgraph optical method. From above thing, by making rib more than one piece from one piece, it studied what influence the ribs outside gave the heat transfer coefficients of the central rib.
The pressure sensitive paint (PSP) has become a powerful tool for the surface pressure measurements in the windtunnel testing. This diagnostic method, however, is limited to the time-averaged measurements so far, because the temporal behavior of PSP has not been well understood. Present paper describes the experimental investigations on the time response of three pressure sensitive paints, PtOEP, H2TFPP and PtTFPP. The coating on which the PSPs are painted is a commercial porous silica thin-layer chromatography (TLC) plate. The sudden change in pressure is provided by a shock tube, and the luminescence change due to the pressure rise by an incident shock wave is detected by a photomultiplier. The results indicate that the characteristic response time is found to differ among the PSPs tested, and the shortest characteristic time is on the order of ten microseconds. The effect of the sudden change in gas temperature on the luminescence intensity is also investigated by using the contact surface of the shock tube flow, and it is found that the luminescence intensity depends only on the wall temperature and is affected little by the gas temperature.
Displacement Ventilation offers improved air quality and high ventilation effectiveness, and reduces air-conditioning costs relative to conventional Diffusion Ventilation. However, it is difficult for traditional techniques to measure flow velocity, temperature and tracer concentration to evaluate the characteristics of displacement ventilation since it is influenced by natural convection and has a complex flow field In this study, a series of experiments to measure flow velocity, temperature and tracer concentration distribution was performed for geometrically similar scale water tank model of room space equipped with displacement ventilation by applying image processing techniques. The distribution of local air exchange effectiveness was calculated from temporal change of tracer concentration distribution by the step-down method. It was confirmed that PTV for velocity measurement and tracer concentration measurement for local air exchange effectiveness calculation were useful to evaluate the characteristics of DV The dynamic range of liquid crystal thermometry should be expanded.
The authors proposed the new propulsion system and the method of performance improvement by blowing moist air for a water jet ship in previous papers. The performance of the water jet ship by blowing moist-air into the nozzle was investigated and it is found that the thrust increased about 20% in comparison with the thrust by the conventional method in a former paper. In this paper, the flow visualization experiment by PIV method was performed to make clear the reason of the increase of the thrust by blowing moist-air. From the analysis of velocity vectors, it was found that the steam blown into the nozzle condensed just after the outlet and that the acceleration of water flow was remarkable. Accordingly, the average density of fluid increased by the increase of density. Therefore, it is clear that the thrust increased by using the moist-air.
The super-heater (SH) tubes in an incinerator have been locally corroded by nonuniform partially accelerated gas flow. It effects maintenance and cost performance. In order to level the gas velocity at the super-heater entrance, putting a baffle in a boiler may be effective. The leveling effect of a baffle was studied by using a three-dimension model and employing PTV (Particle Tracking Velocimetry) analysis. After some trial and error, a baffle configuration was found to give the reduction of maximum velocity and standard deviation of the gas flow.
Visualization and its image processing technique for PIV(particle image velocimetry) are carried out to apply the flow problems in the console. Recently, cooling problems caused engineers great efforts to solve for various electronic equipment, especially for OA equipment, such as copying machines and printers which have fixing process with high temperature. The whole flow field inside the console. is difficult to know by a numerical simulation and a common measurement for its complicate geometry, though analyzing the precise characteristics of the flow is important for energy management. PIV is a suitable flow measurement system for such flow problems.
The impingement of a streamwise vortex on a fin is investigated experimentally with high-image-density particle image velocimetry (PIV) and dynamic pressure transducers in order to relate the structure of vortex breakdown to the spectra of surface pressure along the fin. The instantaneous and ensemble-averaged distributions of vorticity from PIV show strong concentrations of vorticity along the edges of the breakdown region. Correspondingly, the amplitude response of the pressure spectra is the strongest when the fin is located near the edge of vortex breakdown. The dominant frequency of the surface pressure is insensitive to cross-stream displacements of the vortex axis relative to the leading-edge of the fin. Spectra of surface pressure at crucial locations on the fin are related to these features of the instantaneous and averaged flow structure.
The Japan Atomic Energy Research Institute is developing a MW-scale spallation target system under the Neutron Science Project. A cold moderator using supercritical hydrogen is one of the key components in the target system, which directly affects the neutronic performance both in intensity and resolution. Since a hydrogen temperature rise in the moderator vessel affects the neutronic performance, it is necessary to ensure the smooth flow of hydrogen while suppressing the recirculation and stagnant flows which cause hot spots. In order to learn the flow pattern of the impinging jet flow and the flow induced by the jet, the experiments using the acrylic model simulating the moderator vessel, were carried out under water flow conditions with a PIV system. In parallel with the experiments, the hydraulic analyses were carried out with the STAR-CD. Both the experimental and analytical results showed the recirculation flow clearly. And the analytical results agreed well with the experimental results.
The self-induced sloshing in a rectangular tank had been investigated experimentally by using Particle Imaging Velocimetry (PIV) technique. The instantaneous flow fields, time average results and phase average results of the PIV measurement were used to reveal the evolution of the vortical structures in the test tank. Based on the experimental result, resonated oscillation was suggested to be the mechanism of the self-induced sloshing, and the fluctuation of the inlet plane jet and the periodically shedding of the unsteady vortical structures were conjectured to be the excitation source of the self-induced sloshing.
A Variable Orifice Nozzle (VON) by changing a cross-sectional area of the nozzle injection hole, for improving a rate of injection and injection duration, has been developed to study its spray characteristics. Injection and spray pattern responded to the nozzle orifice cross-sectional area which is changing larger to smaller. Transient behavior of the sprays was recorded by two-frame CCD camera system which is based on a microscope with a long working distance. The analysis of the diesel spray velocity vectors were conducted using PIV analyzer with cross-correlation method. The system has been used with various techniques to provide a powerful tool for spray analysis.
The method for measuring the shear stress distributions over the fan blade is proposed by using the oil-film visualization technique combined with the image analysis. The visualization experiment is carried out in a water tank and the surface velocity of the oil-film over the blade surface is measured by cross-correlation algorithm applied to the two images with a certain pattern displacement. The transformation of surface velocity to shear stress is made by a well known shear stress distribution over a rotating disk, which allows the correction of centrifugal force effect on the surface velocity of the oil film. The shear stress distribution and the limiting streamlines over the fan blade are measured and the performance of the fan is studied.
The cavity flow is not only a fundamental problem in fluid dynamics, but also an important engineering problem. One of the actual problems of the cavity flow is pressure disturbance or acoustic noise generated in a duct with a cavity. The fundamental mechanism of pressure disturbance or noise generation in the cavity flow has been investigated. However, the structure of cavity flow depends on the shape of it and the flow condition in the duct. The flow in an axially symmetric cavity is not the same with the flow in a rectangular cavity. In this report, the flow in an axially symmetric cavity is investigated experimentally by using high-speed-video PIV. The results obtained by time series measurements of the flow show that the unsteadiness of the cavity flow depends on the cavity ratio and the circumferential structure of the flow must be considered.
It is well-known that the efficiency of capturing velocity vector in 3-D PTV is much lower than in 2-D PTV due to the problems in particles' occlusion, stereo-matching process, as well as the resolution of the optical hardwares. A new method for particle tracking velocimetry by using a color illumination device with only one camera has been proposed in the present paper. The information of color gradation in the depth direction is employed to determine their 3-D coordinates and velocity components. This report describes the performance of the present method, which is examined by measuring the 3-D flow field of a simple rotating flow.
In Particle image velocimetry (PIV), it is necessary to analyze a lot of images at the same time to increase the amount of information, to improve the measurement accuracy or to understand the compound three dimensional flow field. When the analyzed image is increased, however, a lot of computing time is necessary since the amount of information increases rapidly. In this paper, a simple algorithm was described to obtain the three dimensional flow velocity from thousands of sequential image data obtained by a high-speed video camera. Though only one video camera is used, the measurement of the three-dimensional velocity vector distribution in the two-dimensional sections is enabled by measurement of the time interval which the particles pass through a multi-layer laser sheet.
As a method of 3D-measurement of air flow velocity distribution from the images visualized with smoke particles, we have proposed the method that calculates 3D-velocity component from the gray level defference between two paralel planes.In this paper, we proposed a new image taking method to reduce measurement errors and inspect its performance through the application to CG(Computer Graphic) images.Moreover, the effects of some improvement such as 2D pattern tracking in subpixel accuracy and a new critical condition to eliminate doubtful 3-D component, are also inspected.
As to 3-D flow visualization, many methods such as PIV were developed. In these methods, however, it seems to be difficult to understand the geometrical relations of these analyses. Morever, many constraints seems to be imposed on taking pictures of the flow. In this paper, a new method of 3-D flow measurement through descriptive geometry is proposed. From one pair of photos of flow with a square reference, the camera position and 3-D flow velocity can be calculated. The utility of this method is recognized through the measurement of several models. The 3-D flow around a small type of axial flow fan were measured.
A new image processing technique for three-dimensional measurement of fluid velocity field is proposed in this paper. The technique is based on cross-correlation method and requires gray-level digital data of three-dimensional flow field. They are reconstructed on the EWS from the series of pictures that shows vertical section of flow field visualized by moving laser light sheet. One of the matters with this technique was that it took huge computational processing times. To reduce this problem, the program code is parallelized with MPI, standard portable message passing system. This technique is applied to vortex flow. And the results are compared with the results measured by LDV.
The gradient-based method, in which an optical flow (a velocity vector profile) is obtained from spatial and temporal image gradients, has been often applied to not only PIV but also Robot Vision just because it has a high spatial resolution. In the method, a two-dimensional velocity vector profile is measured by solving an basic equation based on the relationship between two velocity vector components and the image gradients. The method, however, needs another restraint condition because two unknown velocity components are not obtained by solving just one equation. We propose a new method using an artificial neural network for learning vector fields by which the above problem is solved. The neural network is trained by using spatial and temporal image gradients as teaching data so that the basic equation for the gradient method is satisfied. As the neural network itself learns the stream function, the continuity equation of flow is consequently satisfied in the measured velocity vector fields.
We have proposed a new method using artificial neural network for estimating the whole flow velocity vector fields from measured velocity vectors. The neural network is trained by using measured velocity vectors as teaching data so that the derivatives of a certain scalar function agree well with the measured data. The continuity equation of flow is consequently satisfied in the estimated vector fields and the scalar function gives the stream function. In this paper, the method is evaluated using the PIV standard images which are able to give a correct vector field. The following facts are consequently proved. 1. The method is effective to measured fields with sparse velocity vector data. 2. Error estimation rate is improved by patry eliminating estimated data on the periphery of the image.