In order to grasp the state of heat genelation from power cables laid in utility tunnels, we are studying about natural convection in horizontal double cylinders modeled after the utility tunnel. Thermally sensitive liquid crystals are usefull for experiments of the natulal convection. This report shows that an incidence angle of a ray from a slit and the suspension density of thermally sensitive liquid crystals in water were examined with image-processer in order that the colored video image of the themally sensitive liquid crystals was converted to temperature distribution. For application, the temperature distribution in horizontal double cylinders are measured.
Natural convective heat transfers on IC pachage type resistance elements were made clear by the experiments in silicone oil. Temperature distribution and flow pattern of natural convection around resistance elements on the vertical circuit board were made visiable with the liquid crystal particle suspension method. Natural convection of resistance elements were shown by the relation between the heat transfer coefficient and temperature difference. The velocities of silicon oil around the elements were measured with the path lines of liquid crystal particles. The heat transfer characteristic of 30mm space of resistance elements and 6mm space were the same approximately and the mean velocities were not different in the two cases.
Liquid crystal suspension is now widely used for the simultaneous visualization of the flow and temperature fields. To the authors' knowledge, however, only the natural convective fields have been investigated. In the present study, the visualization of a forced convective field was attempted. A heated cylinder was placed in an open channel filled with silicon oil. The fluid was circulated by a rotating waterwheel. The flow and temperature fields of the vortices behind the cylinder were successfully visualized by the liquid crystal suspension.
The purpose of this study is to investigate thermo-hydraulic behavior of a fluid region confined in a parallelepiped cavity equiped with a heater and a cooler. A completely transparent experimental test section was made to visualize temperat-ure and flow behavior using the liquid-crystal suspension method. Thermal plumes from the heater and cooler, global natural circulation in the cavity and thermal startifications were observed and combined to form complicated distributions.
This paper presents the visualizations of electric field distribution and tolerance for insulation strength of a high voltage insulator in order to build a support system for its insulation design. The system has four parts, pre-processing, electric field analysis, post-processing and data base of insulating materials. The solution method for electric field problems is based on the finite element method using personal computers. The part of post-processing enables us to easily understand the electric field distribution and the tolerance for insulation strength by means of the computer graphics. The visualization of the electric field distribu-tion and the tolerance for insulation strength is useful as an aid in designing high voltage insulators.
A numerical calculation technique is presented in this paper in order to calculate the lines of electric force and equi-potential contours in axisymmetric three-dimensional fields by means of inversible visual method. The inversible visual method is based on "the inversibility of potential flow fields", in which the lines of electric force and equi-potential contours can be exchanged each other. In this paper, an application of this technique to electric fields is illustrated by calculating lines of electric force and equi-potential contours around a suspension-type insulator. It is concluded that the presented technique is effective to calculate the lines of electric force in the fields such as composite dielectric substances with complex boundary surface of different dielectric constants.
Three-dimensional unsteady numerical flow field is visualized by using MPGS which is the multipurpose graphic system developed by CRAY research Ltd. The flow field computed by large eddy simulation (LES) is the turbulent flow over a backward facing step, The Reynolds number based on step height and main flow is 46000. Unsteady behavior of the large eddy on the computed flow field is clearly confirmed by making visual animation. Multipurpose graphic system, by which visual animation is easily produced, is available to estimate the computational unsteady flow fields.
A rendering system was constructed for three-dimensional visualization of a direct numerical simulation data base of two-dimen-sional turbulent channel flow. It was based on a method of approxi-mating complex contour surfaces with minute polygons. Instantaneous velocity and temperature fields were visualized. Quasi-coherent structures, such as low-speed streaks, vertical structures, ejec-tions and sweeps. were identified. It was found that the quasi-coherent vortex structures near the wall played a primary role in the production of instantaneous Reynolds shear stresses and turbu-lent heat fluxes.
Molecule motion is visualized by sequential expression of molecular position at each time step in direct simulation of monte carlo method. Exhausted gas molecules from a nozzle are impinged on a circular disk, held perpendicualarly and coaxially with the nozzle. Few molecules do not intrude into the rear region of the disk.
Numerical and experimental studies were made on free convection heat transfer around a domestic electric refrigerator-freezer surrounded by walls. Numerical analysis, flow observations, velocity and temperature measurements were made. Air flows in under the refrigerator and is heated up by a compressor behind the refrigerator. Air goes up in the back space and flows out at the top of the refrigerator. Air circulates around a refrigerator by free convection. The flow rate of the circulation decreases proportionally with the decrease of a space behind a refrigerator. Flow patterns obtained by numerical analysis were found to be in good agreement with the results of visual observation of the air. Velocity distributions obtained by numerical analysis were also found in good agreement with the measured.data. Numerical results were verified to be useful to predict flow pattern around a refrigerator-freezer.
As a simple model of the large scale structure in the laminar boundary layer, the development of the disturbance is calculated by using a three-dimensional discrete vortex method. The filament is stretched by the streamwise velocity and the top region of the disturbance is deformed by the induced velocity. As a result, the velocity profile of the boundary layer is influenced as the disturbance develops. The initial disturbance stretches in the downstream direction, the hair-pin shaped structure deforms and unique vortex ring pinches out from top region of the deformed vortex filament.
A cell averaged large-eddy simulation model is used to calculate the confluence flow with vertical intersection in the channel. The finite difference scheme used in the simulation is that of fractional volume of fluid (VOF) method. A simple SGS turbulence model is used and large scale eddies are computed directly. The computational, results for discharge ratio of branch channel to main channel Qr=0.6 with the same kind of channel width ratio Br=2/3 at Reynold's number Re=90000 are presented and compared with experimental results. The velocity field, recirculating region and the large scale structures of the confluence flow are well simulated.
The fundamental behavior of transient jet which is injected into quiescent fluid are investigated by the Finite Analytic Numerical Method. In this study the continuity equation and the Navier-Stokes equations are solved as the two-dimensional imcompressible fluid flow. The main results obtained can be summarized as follows. On the jet axis, the position of the maximum for the axial velocity, the minimum for the pressure and the section through the two vortex centers agree almost irrespective of time and Reynolds number.
Numerical investigation was carried out for three dimensional natural convection in a cubic room. Thermal radiation effect due to the walls of the enclosure was considered. Compared with the case for natural convection only, the natural convection associated with thermal radiation created stronger secondary flow which, in turn gave more uniform temperature field resulting some what weaker heat transfer rate.
The MOCVD technique is one of the most excellent process for the growth of III-V semiconductor epilayers. In this process, epilayer quality(i.e. thickness uniformity) is determined largely by gas-flow dynamics in the reactor.An understanding of gas-flow patterns in the reactor is necessary to obtain the good uniformity of epilayer on a large scale. In this study, we developed a new method of generating micron sized TiO 2 particles by the 2-step reaction of TiCl 4.Using this technique, TiO 2 particles are generated very smooth and thick.We visualized by the scattering of a laser light sheet in a vertical reactorr with top inlet, and could observe stable gas-flow patterns for more than 30 minutes. The experimental results indicate that the fine gas-flow patterns on the 2-inch diameter substrate affects the thickness uniformity strongly.
The gradient of water surface is measured by using the reflected light from the water surface and an optical grid in this study. The shape of the water surface is calculated from the obtained data of the gradient of the water surface.
The turbulent velocity components (u, v) at 11 points in a reciprocating oscillatory turbulent flow have been recorded simultaneously by a set of eleven X-type hotwire probes located in a plane perpendicular to the mean flow. Using the conditional sampling technique and a new method of data analysis for the inverse estimation of flow field called the " virtual plate/load and mascon model", we reconstructed the quasi-instantaneous three dimensional image of the large-scale structure of turbulence (expressed in terms of the velocity components u, v, w). The image has been further clarified by the perspective representations visualized by the computer technique in terms of time-lines and streak-lines of fluid particle tracer. This may be the first proof of the instantaneous coherent turbulence structure directly derived experimentally from velocity measurement by probes such hot-wires and LDV.
In the 3D particle tracing velocimetry(PTV), a set of simultaneously taken pictures are referred frequently to measure 3D coordinates of tracers. If two or three simultaneously taken pictures are recorded together, the analysis can be perform efficiently. Authors have developed such a device for 3D PTV, and found some interesting applications which are useful for the purpose. The principle of the device is to divide a NTSC picture into two parts by making use of high speed multiplexer. Three partition modes such as vertical, horizontal and fieldwise partition, can be available according to applications. A vertical partition mode may be employed most commonly in 3D better spatial resolution, and a horizontal one may adequate for stretched field of view like a flow in a pipe. The fieldwise partition may be used for interesting purpose, such as the 3D presentation of 3D vectors as well as the adjustment of positions or directions of two cameras.
A method to make microcapsules which are filled with pure water and covered with thin film of polystyrene was developed. The best temperature for making the microcapsule lies in a range from 30°C to 40°C. Their mean specific gravity and mean diameter were 1.0064 and 295 μ m, respectively.
A new thermal radiation technique had been developed to detect internal flaws of mortar structure, such as building, bridge, tunnel and so on. The present study shows that stepwise solar energy was injected to the tested plate with artificial internal flaws. Transient radiation temperature image of the slit flaws on the CRT of the infrared radiometer was represented and visualized by means of the existence of the flaws with the higher equivalent radiation temperature above the flaws than that of the flat surface. In this report, it was clear that the temperature rise of the flaws was increasing with increase in width b and depth H.
The dynamic behavior of two cavitation bubbles was observed by means of a highspeed photography. Two model bubbles were simultancusly produced by focusing a laser pulse into water. The motion of bubbles was photographed using a diffused illumination of back lighting with a diffuser. A schlieren technique was applied to visualize shock waves emmited from bubbles. The experimental results were compared with the numerical predictions obtained from a boundary integral method
This paper describes a new method for visualizing three-dimensional shock shapes around hypersonic vehicles by using an electrical discharge. The method is based on the following ideas: When an electrical discharge is generated across a shock wave, the shock wave can be seen as a dark portion in the electrical discharge. The three-dimensional shock shape can be visualized by taking a discharge photograph in the rear direction of the flow. In this paper, shock shapes around various kinds of hypersonic vehicles were visualized. Those visualized results prove that the present method using the electrical discharge is useful for visualizing three-dimensional shock shapes.
The purpose of this study is to investigate the nature of the flow in the passage between two coaxial cones by flow visualization, carried out by means of paraffin mist and a laser light sheet. The flow passage in the present study is one of the special cases of a radial flow system. Similar to the previous results for radially, outward flow between two parallel disks, it was confirmed that the periodic axisymetrical circular vortices are also generated in the flow through the present annular-conical passage.
Flow visualization of air flow in a sharp 180-degree turn of a square cross-section duct was conducted using paraffin-mist as a tracer. In the previous paper, it was shown that there exist a large-scale 3-dimensional flow structure accompanied by a strong reverse flow along the surface of the outer corner, and a strong secondary flow in the entrance of the first turn. In the present experiments, we observed the cross-sectional views perpendicular to the flow axis using a laser light sheet. It was found through the present study that at the plane of 30-45-degree of the first 90-degree turn a pair of vortex starts to appear. At the outlet region of the second 90-degree turn four vortex pairs are found to be existing.
The purpose of this study is to clarify the flow pattern in the curved diffuser and to improve its performance using dye-streak method. In this study, when the diffuser inlet velocity profile is increased towards the diffuser convex wall, the effects of the interposed position and position of leading edge of a guide vane on the flow patterns in a logarithmic spiral curved diffuser are clarified by. the flow visualization using dye-streak method, and streak lines obtained are compared with the numerical solutions obtained by the finite element method. As the results, it was found that the flow patterns obtained by the flow visualization agreed comparatively with numerical results, in case a guide vane was interposed and the performance of the curved diffuser was affected considerably by the position of leading edge.of a guide vane.
The conventional tuft method frequently suffer from a self-excited flag waving instability which interferes with operation of tuft. A tuft method being used for this investigation is developed to avoid this. The averaged flow pattern in cross section across outlet flow of reguler pyramidal diffuser, in which unsteadily flow, is visualized by the improved tuft grid method, and recorded by using the photographic film and video imaging. The diffusers are presented for following condition: length ratio N/W=10 and total divergence angles 2Θ=6°and 8° On the other hand, to determine the frequency content of the pressure unsteadiness, power spectrum were computed from recorded unsteady main flow pressure data. It has been shown that higher pressure recovery occurs when mild oscillating flow exists in the outlet flow.
A pump of rotary type using the Weis-Fogh mechanism, which is a mechanism of lift generation in the hovering flight of small insects, was studied numerically using the discrete vortex method. A velocity vector field around the rotor were obtained. A flow visualization, using air bubbles as the tracer, was also performed using the pilot pump. Stable vortices which appear commonly in tangential flow pumps were found near the rotation axis inside the rotor, and the vortices were simulated by the numerical calculations.
Flows past a rotating circular cylinder was investigated by using the dye injection method, and a computer simulation using the Vortex-in-Cell method was carried out. Results obtained by the two methods showed a good agreements. We found out that the Strouhal number increases and the width of the wake decreases as the spin parameter, which is the ratio of the peripheral speed of the cylinder to the uniform-flow velocity, increases. It is also shown that the predominant frequency of the wake, which corresponds to the frequency forming the Karman-type vortices, depends strongly on the Reynolds number.
Studies on impinging jet have been previously tried about analysis of flow and heat transfer fields produced by jet impingements according to materials on which jets impinge, but there are few example to visualize them systematically. Some trials have been especially reported in a limited field in case of vertical impingement except obligue one. In past time, the authors have clarified the effects on initial turbulence level and Reynolds number of a two-dimensional free jet to impinge vertically on the wall plate by use of the Schlieren optical technigue. This paper explains the interaction between mixing layer and boundary layer, and transition process appeared in the stagnation boundary layer by the cbligue impingements of a two-dimensional free jet by a lot of the /schieren photo graphs.
The present paper describes the observation of horseshoe vortex around the jucnture, between flat plate and circular cylinder. In the case of inclined cylinder, the three-dimensional separation region in front of the body is smaller and the flow stability is stable. The milk-painting method is useful for visualizing the flow field in laminar flow and also the limiting streamline in turbulent flow. The oil-film method and the tracer method are also applied for observation of this flow.
As a part of the research to prevent collision of a ship to a bridge under gale condition, the authors carried out the model tests. Wind velocity distributions around the bridge model are measured by hot-wire anemometer and the air flows around the bridge model are visualized by using smoke-wire. Finally, they made clear the behavior of a ship in the vicinity of the bridge under gale condition by calculating ship movement using wind data obtained in the model tests.
Studies of seeing conditions inside telescope domes indicate a need to provice substantial air ventilation to prevent image degradation due to thermal variation of the air within the dome that means fluid-dynamic designing is necessary for choosing dome style. Althoughthe traditional enclosure is a cylinder topped by a hemispherical dome, alternative style such as flat-loof or tapezoidal topped cylinder could be considered from view point of fluid dynamic feature. Significant flushing flow without thermal ground boundary layer coming into the dome is the subjects to investigate. Water channel tests were made using 3 Types of 1:500 scale enclosure models with flow visualization methods. Dye injection method was mainly used and some quantitative measurements were done. Among the models, the cylindrer with near-flat roofs appear to be superior. And the sidewalls on either side of the telescope were found to be beneficial for flushing the flow.
Almost all studies of surface buoyant jet are treated the spreadings in the case of infinitely deep water bodies. This study aims to be clear the behavior of surface buoyant jet dis-charged on the sloping bottom which is very important case for engineering aspects. The phenomena caused by the interaction between sloping bottom and buoyant jet such as (a) the intrusion of quite thin density wedge along the bottom, (b) unstable vor-tex, (c) generation of internal wave at downstream of unstable vortex, (d) drawing down of density interface due to low pres-sure, are reported and discussed.
The stratified flow past an isolated mountain was produced by towing the inverted body through saline-water solution with linear density gradients. The Froude number Fr(=U/NH) and Reynolds number Re(UH/ν) where U is the towing speed, N is the Brunt-Vaisala frequency.H is the mountain height, and ν is the kinematic viscoaty.were in the range Fr<1 and Re<1500. The flow in such ranges as it corresponds with the real atmosphere. Flow visualization techniques by the color dye infection were used tograsp the global structure of this flow. Two kinds of ph indicator was solved in the tracer as chemical of coloring. And we obtained a conclusion that the flow can be divided roughly three patterns. Quantitative measurments by the density probe clarified in the detail the three dimentional figure of the internal gravity wave.
The behavior of interfacial wave on liquid film in vertically upward airwater annular flows has been observed and analized by a pigment luminance method. As a result, it has been shown that interfacial waves were apparently classified into three types, i.e. a base wave, a high-speed wave and a disturbance wave in terms of their wave-forms and propagation velocities. The base wave exists at any time and any place. The high-speed wave has the fastest velocity of the three and often appears behind the disturbance wave. The disturbance wave is a group of many kinds of interfacial waves and alternately merges and splits.
In this paper, the motion of surface-floating particles in a straight and a curved channel is experimentally and numerically studied. The purpose of this study is to confirm the validity of the modified B.B.O. equation and to investigate the role of the dimensionless parameter t./Cd in particle tracing.
Experimental analysis of flows in a heater unit of automo-bile air conditioning system is very important for fundamental design, improvement of efficiency, noise control and so on. In this report, velocity measurements and visualization of flows in a heater unit produced by different operation modes are carried out by means of the dual-beam-sweep laser speckle velocimetry and laser-light-sheet method, respectively.
In the present paper, holographic interferometry was applied to visualize of three dimensional shock wave phenomena. One of the examples is a shock wave discharged from the open end of a square cross sectional shock tube. The experiments were conducted in 40mm×40mm cross sectional shock tube. Double exposure diffuse holographic interferometry was used for the flow visualization. The three dimensional shock configulation and the three dimensional flow behind the shock wave can be clearly observed. Other three dimensional observations in shock tube flows are also shown.
Laser-induced fluorescence (LIF) method was used to visualize and measure velocity profiles in pulsatile water flow through a 180°curved tube of square cross section. Visualization and quantitative mesurement of velocity profiles across the tube was made at eight different phases in one period of the pulsatile flow at five different cross sections along the curved tube. As a result, the instantaneous velocity field was clearly visualized and measured. Furthermore, stere, ographs of instantaneous velocity profiles and instantaneous contours of equi-velocity in a u-bend at θ=180° was obtained from the instantaneous velocity profiles in a pulsatile flow.
Generally, the density change ofaliquid is measured using the change of elecldcal conductivity. The conventionaldensity meter has the deficits that the probe itself disturbs the flow field and it can measure only the density change at the point. The my path ofalaser beam is deflected when it is shed into a strntifeid fluid due to the change of the deflectionratio of ligllt by the density difference of liquid. In many cases, this is unfavorable property for the flow measurement. This reserach aims at the development ofanew type density meter using this property. Afunctional form such as the polynominals, the Fourier series and other orthogonal functions which contain a fewarbitrary parameters is assumed to express the density filed. The path of laser beams are calculated by solving thedifferential equiation ofray deflection. The true values of parameters are invecsly estimated by the Marquazdt methodso as to minimize the squared errors between the calculated and measured points oflaser ray emmision. The position of lase ray emmision is measured precisely and quickly by PSD (Position Sensing Dcvice). The direction oflaser beam is changed by the combination of a rotating mirror and reflection minors, in order to increasethe amount of information, i.e. the number oflaser rays. The density chnges ofstratifeid flow are correctly estimated for (a) one dimensional vertical density filed, (b) the internal waves of two-layerd flow and (c) complicated density field around an isolated mountain ridge.
The digital image processing has been developed for a time series measurement of whole field velocity using the cross-correlation technique. The flow field illuminated by laser sheet were taken by CCD camera, and obtained images were recorded on the VTR with interval of 1/30sec. Individual images were transferred from VTR under the control of personal computer to the image grabber. The calculation of the cross-correlation was performed by fast DSP for the evaluation of velocity vectors. The time series analysis of the system showed good agreement with those of simultaneously applied LDV measurements. The system applied to the thermally stratified shear flow in a horizontal pipe provided instantaneous and time series whole field velocities from 1400 planes(47sec), and motion of eddies were revealed from this measurement which was unable to measure by point-measuring techniques.
A pair of aerial photographs of flood flow of Ishikari River were analysed by picture processing to obtain two-dimensional distribution of velocity vectors of the flood surface. Streamline patterns, vorticity and divergence were calculated using the obtained velocity data and the structure of the vortices and its relation with river sedimentation were elucidated. Strong upwellings (boils) in the vortices and strong downflows around the edge of the vortices were shown to be the main cause of the formation of the core of scroll bars.
This report is on a new velocity measurement system which can measure and display velocity vectors in real-time by processing the B/W video signal. Its measuring rate is 1/60 sec for 16 areas. The method of the determination of velocity vector is a 2-dimensional correlation technique of binary video data. The system is realized by developing a gate-array (LSI) which calculates 1-dimensional correlation coefficients of horizontal 16 points and a hardware which uses the LSI for processing the video signal to calculate correlation coefficients of horizontal/vertical 256 points at the rate of the video field. This report shows an evaluation of the system by using deviation analysis. And some measurement examples of velocity distribution and transitional velocity are presented.
The purpose of the present study is to propose a new high efficiency particle identification method for 3D PTV, based on a binary cross correlation method and its necessary condition. The effects of sizes of imaginary particle, search subregion, and identification subregion on the particle identification efficiency are discussed through numerical simulation.
Accuracy of the correlation method is examined by simulating tracer particle images which follow uniform or shear flow velocity distributions. Velocity differences between given and calculated values are examined for various sizes of reference frames. Also, two methods for obtaining intermediate particle positions between the centers of pixels are presented. One of the methods uses linearly interpolated intensity of the image between pixels (Method A) and the other utilizes the distribution of cross-correlation coefficients (Method B). Both methods are found to be effective in improving the accuracy of the correlation method.
In this paper, we propose a model-based method of estimating the velocity of a moving object from a series of images. Assuming that the motion is described by an affine transformation, we construct a discrete-time state variable model of the motion based on the dynamic motion imagery modeling technique proposed by Schalkoff. Using this state variable model, we derive an adaptive Kalman filter algorithm to estimate the velocity. Some estimation results are presented to show the effectiveness of the proposed algorithm.
A quantitative full-field velocity measurement system based on the digital image processing technique has been developed for analyzing high Reynolds fluid flow. The experimental system consists of a corded illumination source, a high speed image processing algorithm and a PC based image processing computer. Flow field visualized by fine tracer particles. By controlling synchronaization between the irradiation of a laser sheet and the NTSC video signal, descriptive information is obtained on consecutive TV images. Flow visualization images are generated using this optical technique which allows to track high-speed tracer particles. To confirm the ability and utility of this technique, the high Reynolds fluid flow (Re=1*10 4) inside a casting model has been investigated
Three-dimensional measurement data in flow fields obtained by image processing are visualized using computer graphics technique. The CG representation help us to understand flow characteristics from the measurement results obtained. The CG represents time series of 3-D tracer particle positions, 3-D path-lines, and 3-D velocity vector distributions in a uniform flow and a flow around a sphere in a water channel.