There have been so many optical observations of aurora so far, but there have not been adequate quantitative interpretations of their causality between the source (auroral energetic particles), the resultant auroral volume emission rates, and the fields. Difficulties of these studies are in the fact that (1) observationally, we have not obtained simultaneously and quantitatively physical quantities of the source, the resultant emission and the field, and (2) theoretically, we have not fully understood the physical processes of auroral emissions. Recently we have performed some experiments which give us some physical parameters related to these problems. On the other hand, the computer simulation schemes to calculate the photoemission rates from the source particles have been developed. In this review paper, I will present some examples of the auroral observations and give a talk what kinds of theoretical works we are now investigating; Particularly following five themes are discussed. Rocket experiment, spectroscopic observation, stereoscopic observation, satellite observations and computer simulations.
Advances in flow visualization techniques and their applications to engineering turbulence research are reviewed from a viewpoint of whole field measurement. Beginning in the early 70's, this important field of science and engineering has observed several important breakthroughs such as flow structure studies with sophisticated tracer methods using hydrogen bubbles, smoke-wires and liquid crystals, development of three-dimensional particle imaging velocimetry, its extension to measurement of object motion/deformation, and visualization of databases provided by large-scale numerical simulations. The future scope should integrate a rapidly spreading cyber-space on the worldwide network as well as extensive exploitation of valuable assets of flow visualization in not only science and engineering, but also education and culture.
The history of medical imaging techniques began with the introduction of a method of diagnosis 100years ago and this diagnostic goal since been met in many ways. Quantitative scientific visualization in 3D and 4D is not only useful for diagnosis but also for more extensive applications such as surgical planning, treatment planning and surgical support systems. Medical 3D and 4D imaging devices have led to the development of numerous techniques and software according to clinical demands and the numbers of such advances have been increasing rapidly in recent times.
The time sequential measurement technique for three-dimensional density distributions in a channel was evaluated. Using the holographic interferometer, information of the density distributions were visualized as fringes. In the real time method, the wave before disturbance is recorded on a hologram, then the hologram is developed at the initial set position. When the hologram is reconstructed, the fringes are caused by the interference between reconstructed wave of the undisturbed field and wave through the disturbed field. Since the reconstructed wave contains the information of the undisturbed field including the channel surface refraction, the fringe pattern represent only the optical phase changes inside the channel. However it is usually difficult to develop without movement or shrink. Using the photoconductor-plastic processed by solvent vapor, the hologram can be developed without any movement. In this study, buoyancy driven exchange flow of air and helium gas were measured using real time hologram with photoconductor-plastic. The transient three dimensional density distribution of buoyancy driven exchange flow are reconstructed, showing the effectiveness of the proposed technique.
Doppler Global Velocimetry (DGV) is one of the quantitative flow visualization methods of flow velocity. The frequency of the reflected light by the particles in a high speed flow is shifted by the Doppler effect. DGV measures the Doppler frequency shift using Absorption Line Filter (ALF). In this paper, a free jet velocity field is visualized by DGV. An argon-ion laser and an iodine cell are used as the light source and the ALF. The velocity of the free jet is about Mach 1 and the water vapor is used as tracer.
Experimental results are presented on visualization of two-phase flow in capillary heat pipe by using proton radiography. Proton radiography is non-destructive testing technique making use of the difference in attenuation characteristics of proton beam in materials. 12MeV Proton beam is generated from Tandem accelerator. Beam diameter is 20mm. Proton beam passing through the test section are converted to visible light by fluorescent screen. Heat Pipe is thin-plate type (190mm X 50mm, 1.3mm in thikness), and 0.6×0.7mm channel is snaking in it. Normal speed video camera (recording rate is 60 frame per second) and high speed camera (1000 frame per second) are used. Small bubbles whose diameter are less than 0.6mm can be visualized clearly and recorded with the rate of 1000 frame per second.
Rarefied gas flows through the circular tubes with a finite length were numerically simulated by the Direct Simulation of Monte Carlo method. The effects of boundary conditions, such as accommodation coefficients and surface temperatures at the solid surfaces of the tubes are discussed. The rarefied gas flows covered are the range from rough vacuum to extremely high vacuum conditions. According to the results of free molecular flow, the transmission probabilities increase with decreasing momentum accommodation coefficients. On the other hand, the probabilities increase with decreasing the surface temperatures.
The fine particle plasma means both of a dust plasma and a dusty plasma. The aluminum fine particle plasma was generated by a boat method and by an irradiation of halogen light. The typical size of aluminum particle was 1 μm. The macroscopic motion and alignment of plasma were observed in the electric field. Plasma density was determined by the observation of transmittance of He-Ne laser light.
In recent years, the use of a natural gas expands to a new energy source. The generation of carbon dioxide from a methane is less than an old fossil fuel. But the storing efficiency of a natural gas is not enough because the methane which is the principal ingredient of the natural gas is a gas in normal temperature and the normal pressure. However, since the methane hydrate contains greater methane than the volume of the methane gas by 100 times, if the methane is made from the methane hydrate the storing efficiency is greatly improved. This paper discusses the behavior of the methane molecules and the water molecules depending on the conditions of the temperature and the density by the computer simulation used Molecular Dynamics method (MD method).
A opto-microengine is composed of a vacuum chamber, a micro-rotor, and optical beam generation devices such as a laser beam generator and a floodlight lamp. The optical beam generation devices with a visible light are used as an energy supplier. The opto-microengine is rotated by the molecular gas dynamics effects. The effects are caused by the temperature difference between the backward surface and the forward surface of the rotor. With the increase of the temperature difference, the torque of rotation increases. To increase the torque of rotation, it is important to make the selective optical absorber-plates to absorb more laser light. The selective optical absorber-plates are made of an aluminium plate deposited thin films. To determine an ideal film thickness, the influence of the film thickness on the temperature increase of the surface by the laser heating is experimentally clarified. According to the experiment data, the thin film of 800Å silicon oxide and 300 Å germanium in thickness is effective for heating by laser irradiation.
Gas molecular motion around laser opto-microengines are numerically simulated by the Direct Simulation Monte Carlo method. The flow model for simulation is that four blades rotor of the engines is installed, without rotation, in a computational domain. The domain, a square cavity, is enclosed by solid surfaces with diffused reflection. The backward surface temperature of the rotor is lower than the forward surface temperature by 2 times. It is revealed that the maximum macroscopic velocity around the rotor is dependent on the blade thickness.
In order to clarify the metering characteristics of fluidic flowmeters employing self-sustained oscillation, the oscillating jets of these flowmeters were visualized and the differential pressures across the jets were measured. The experiments clarified that, the oscillation of the target oscillator is influenced and synchronised with the pulsation since the strength of the recirculation vortex flow is affected directly with the pulsation of the jet, then the frequency of the oscillation is matched with that of the pulsation of jet flow.
We examined numerically and experimentally self-sustained oscillation and fluid mixing in a grooved channel for steady flow. Oscillatory flow arises from Tollmien-Schlichting waves triggered by a shear layer between channel and groove flows. Vortex dynamics within the groove lead to efficient fluid exchange between both flows.
The experimental study of the dynamic characteristics of the elastically vibrating flat plate has been conducted in air loading, and a numerical calculation about this problem was performed. In particular the distribution of the air flow velocity near the trailing edge of vibrating flat plate (L=20mm, f0=60Hz) was measured by using LDV, and was calculated by a new method used moving grid code. So we could find the presented calculational method has a potential to solve some Fluid-Structure correlated problems.
To date, flow visualization of the logarithmic spiral curved diffusers have been carried out under various conditions in order to clarify their flow patterns. In this study, the effects of the existence of a rear duct connected at each outlet of the curved diffuser with different spiral angle on the flow pattern are clarified by the flow visualization using the dye-streak method and the condensed-milk method, and their results are compared with the numerical solutions obtained by the finite element method. As a result of this study, it was found that the flow pattern in a curved diffuser was affected considerably by connecting rear duct of a suitable length at the outlet of a curved diffuser, and the flow pattern in a curved diffuser was improved by connecting a rear duct in any logarithmic spiral angle.
The purpose of this study is to clarify the internal flow pattern in several curved diffusers with the different logarithmic spiral angle. The flow visualizations were carried out by smoke wire method using High Speed Video Camera, and their results were compared with the data obtained by the wind tunnel experiment. In this study, the effects of the existence of the rear duct connected at the outlet of the curved diffuser on the flow patterns were clarified by the flow visualization. As a result of this study, it was found that the performance of the curved diffuser was improved considerably by the existence of a guide vane and a rear duct of suitable length, and was affected by the difference of logarithmic spiral angle, and the flow patterns obtained by the flow visualization agreed comparatively with the wind tunnel experiment.
In this study, experiments in two intersecting ducts with a perforated zone inclusive of a splitter are performed to investigate the secondary flow in the perforated zone and the flow rates in the left and right downstream ducts when changing the conditions of the shapes of perforated zone, the intersecting angles and the upper water levels. The flow pattern in the perforated zone is visualized by the particle tracing method. The velocity distribution in the perforated zone is measured by the two-dimensional Laser Doppler velocimetry. The secondary flow and the flow characteristics in the perforated zone are clarified.
A visual experiment of cyclonic and anticyclonic vortices in a rotating frame were carried out. After working fluid was in rigid-body rotation, the vortices were induced by a rotating disk which had different rotation to the container and flushed with an upper lid. The vortices showed two-dimensional columnar motion due to Taylor-Proudman theorem. In our experiment as Kloosterziel et al. and Heijst et al. described, monopolar and tripolar vortices merged, however, as Rossby number increased the vortices lost its symmetry, and vortex structures were found to depend on Rossby number Ro = |Ω-ω| /2Ω and Ekman number Ek =ν / (2 Ω R 2), here ν was kinematic viscosity of working fluid, Ω and ω respectively angular velocities of the container and rotating disk reference to stationary frame, and R a radius of the rotating disk.
The major purpose of the present study is first to propose the definition of the wavelet Reynolds stress using the wavelet transform, in order to study the characteristics of Reynolds stress in frequency space. Then, the fluctuating velocities at various positions in a bounded turbulent jet are analyzed by the wavelet transform and wavelet Reynolds stress analysis. The wavelet Reynolds stress analysis reveals the contributions of the different frequency to the Reynolds stress, which is directly related to coherent structure of various scale eddies
The honeycomb catalysts were used for the de-NOx of diesel engine. The flow uniformity of exhausted gas in the de-NOx reactor effectuates the high de-NOx efficiency and the long life time of honeycomb catalysts. Therefore, it is important to make clear the flow distribution of exhausted gas from the diesel engine. In this report, the flow of inside the de-NOx reactor was studied experimentally by using the smoke method and the smoke wire method for visualization. A baffle was equipped in our deNOx reactor to regulate the flow distribution in honeycombs. As a result, it was made clear that the vortex produced after the baffle had an important roll for flow distribution and mixing.
In scientific visualization, it is necessary to take into consideration the characteristic of human perception. A multisensory data sensualization environment was developed in which visual, acoustic, and touch sensation could be used to display scientific data. This paper describes the calibration method of the sense displays based on psychological magnitude and the intuitive data sensualization methods, based on real world metaphor, augmented reality, and real time simulation techniques.
Unsteady flows around a door mirror mounted on a passenger car were computed using a third-order upwind-difference scheme and an overset grid technique. Aerodynamic noises in far field, emitted from the mirror, were calculated from pressure fluctuation on the surface using Curle's equation. They were synthesized by an Apple Macintosh. Flow were separately visualized on a graphic workstation. Rendered images were transferred to the Macintosh. Those images and the synthesized sounds were edited into a video tape. We could evaluate the aerodynamic noise by our own ears without any physical model and investigate the relationship between flows and sounds in detail.
Higher dimensional space enhances intellectual activity of human beings. 3D graphics contains much more information than 2D graphics. We proposed visual and haptic representation of five-dimensional space. Our 5D space is generated by scanning 3D cube. The user's hand can essentially move in 3D space. We therefor use rotational motion of the hand for scanning 3D cube in 5D cube. The 3D cube is cutting volume of the 5D cube. The cutting volume moves by rotational motion around roll and pitch axis of the user's hand. Force display presents potential field which indicates axis of rotation. The user can easily separate rotational motion from translational motion by force feedback. Usability of the 5D cube is examined through recognition performance tests and we applied the 5D cube to CT data of human brain.
When designing and developing huge software system, developers are required to fully understand the many intricate functions and vast amounts of data which are involved. However, difficulties arise due to the large size and complexity of the software which is necessary for such a system. To address this problem, a software visualization tool was created in a virtual reality environment. This tool helped to facilitate the tasks involving when programming, testing, and debugging software by enabling the direct manipulation of graphical elements representing the structure and code of the software. This paper describes how methods for software development support are achieved using this tool.
A transient flow analysis accompanied by the formation of a liquid droplet using the fluid dynamic program FLOW-3D and the use of an animation display technique are described. The numerical example includes the inkjet analysis and the transient flow analysis of the melting solder to fasten the leads of LSI chips to the printed wires. FLOW-3D has the feature of giving a precise numerical solution scheme to solve the transient flow considering the complex free surface motion which is based on a Volume of Fluid (VOF) algorithm. Especially the VOF is effective for the transient analysis of the dynamic process in the formation of a liquid droplet from continuos liquid. Each picture of the numerical results displayed on the screen of an EWS using the graphic program FLIPS is converted into a bitmap file. The animation display of the bitmap files is performed using an animation program on a PC.
We developed a new type of flow visualization system. In this system, we can check a state of flow fields during calculation. With respect to visualization, Open GL, which is provided in Windows NT system, is employed. Furthermore, combining this system with Perception, we can readily record image data of the visualization for video movie.
Structure of blower fan unit is very simple and gets good performance in respect of high flow rate and moderate pressure gain. But it is noisy especially in high back pressure. Parametrical analysises have been tried to control noise generations, but we cannot cut down noise drastically in such manners for lack of the informations of noise generating mechanisms in the unit. We investigate the noise sources by sound visualization methods and get some hints of noise generation where and how they are in the unit under fluid flow.
Ultrasound is applied to observation to get the structural information in the field of medicine and oceanography. Ray acoustics is helpful to estimate the behavior of emitted ultrasound directly. At present, ray acoustics has assumptions such as infinite frequency. Some considerations on generalizing ray acoustics to lower frequency is introduced here.
Image analysis techniques are now widely applied to measurement for scientific and engineering studies. It has a great advantage in that simultaneous aerial measurement is possible. One disadvantage is that, as the aspect ratio of a TV display is about 5 : 3, it is difficult to visualize the whole span of an object with high aspect-ratio such as cables, bridges, etc. Three techniques are proposed to overcome the difficulty : (1) Employment of a cylindrical lens system, (2) Development of a proper computer algorithm, and (3) Development of a special video camera. The combination of all these three will accomplish simultaneous measurement of whole span of linear objects with satisfactory accuracy.
Acoustic holography method is applied to moving noise sources detection. A noise emitted from a driven car is measured using 64 small microphones array which is set in a lattice state, parallel to the driven direction. Noise source images are calculated from the measured data taking the Doppler effect into consideration. The measurement was carried out to detect noise sources of a driven car. As a result, the obtained distribution showed clearly noises from tires and an exhaust pipe.
As an alternative of microphone array measurement for locating noise sources of machines, a new method to visualize noise sources is proposed in this paper The method is based upon non contacting laser Dopplor vibro-velocimetry applied to the surface of a thin and light film placed closely in front of expected source region. The laser shoots all over the surface by the aid of 2-D scanning mirrors one point by next. This research provides a fundamental characteristics of the proposed method by practical measurements done for two speaker sources as a multiple source model. Regardless of phase relationship between two coherent sources, it was found that the method is applicable with small insertion effect upon sound field and with high resolution ability to multiple sources.
Laser differential interferometry using two laser beams of perpendicular polarization is applied to sound pressure measurements. The weak density difference due to the sound wave no more than 70dB between the two beams is measurable in proportional to the differential output signal of the two photo detecters. Both steady and transient sound wave signals are obtained by our interferometer as clearly as by microphone. Acoustic vibration of the optical systems and the way of sound visualization in future are also discussed.
Our present knowledge of the sounding mechanism in flue organ pipes seems to be well founded and fully evolved through a long history of the research originated by Helmholtz and Rayleigh. However, if we define the sound excitation as the initial change from a nonsonic to a sonic fluid motion, there is no ab initio theory of the sounding mechanism based on such a definition. From this viewpoint a smoked jet in organ pipes is observed by a digital high-speed video camera when the blowing pressure varies from null to a final steady value. The jet displays complicated transfigurations until it reaches to the periodic orderly back-and-forth deflection. During this process some acoustic spectral components are organized in harmonic relation via mode locking in nonlinear systems. Also, the phase speed and amplification factor of the spatially growing wave on the jet are estimated from the visualized shape in the steady-state oscillation.
Aerodynamic pure tone generated from the cross-flow over grooves are studied experimentally. The Strouhal number of the tone frequency is found to be nearly unity based on the free stream velocity and the groove width. Coherence between the generated sound and the velocity turbulence over the two-dimensional groove are analysed by FFT analyser and Personal-Computer for making sources of this pure tone clear. It is found that the center of the source region is in the shear flow layer over the groove, near the downstream edge of the groove.
A preliminary study was made for the development of a new type rain gauge which can estimate the rainfall intensity with a fine time resolution by measuring the intensity of rain sound. A visualization experiment was carried out in order to relate the size of a rain drop to the intensity of rain sound emitted from a tinplate can when the drop hits its roof : Motion of a falling water drop irradiated by stroboscopes from different two angles was recorded by a CCD camera. From the CCD image, in which, the drop appears as a series of a couple of bright points, the drop size and the falling velocity just before it hits the can were estimated. The results showed that the sound intensity was proportional to the kinetic energy of a water drop. Because a natural rain drop falls with the terminal velocity which is determined by its size, the above relation enables us to estimate a volume of a rain drop from the rain sound intensity. The rainfall intensity can be calculated by summing up the volume of rain drops during a unit time.
Air change rates in a house were measured from decay curves of video image signals assuming that pollutant gas could be completely diffused inside a house immediately after the emission of tracer gas. The experiments were conducted using both wind tunnel and actual house. From the wind tunnel experiments, it was found that if the wind speed of oncoming flow were less than 1 m/s, the results of air change rates measured by video images could have good agreements with those derived from decay curves of gas concentrations that were measured by the high-speed hydrocarbon analyzer. For the field tests in a house with shed-roof, the tracer was emitted by smoke tubes, and the decay of particle concentrations were measured by four sets of aerosol monitors. It was achieved that the video image techniques could prove the validity of being capable of measuring air change rates with almost same precious accuracy as the aerosol monitors.
Turbid water intruding into a stratified reservoir was visualized by two kinds of equipment mounted on a boat; Precise Echo Sounder (PES) and Acoustic Doppler Current Profiler (ADCP). By PES, a cloud of fine solids suspended in the water was clearly visualized even if the turbidity was less than 20 ppm. On the other hand, the velocity measurements by ADCP contained a lot of error because of the trembling of the sensor caused by wind waves. The order of the velocity fluctuation at each cell was 5 cm/s while the order of the current was 10 cm/s. However, the resultant picture shows the flow pattern and the velocity distribution in a section fairly well : The turbid water flowed down on the bottom slope as an inclined plume with the maximum velocity of 15cm/s, took off the bottom at the depth of 16 meters, and intruded into the reservoir horizontally along the thermocline with the velocity of 10 cm/s. It is noteworthy that the horizontal stream along the thermocline concentrated in a narrow region in the transverse section although the reservoir water was highly stratified.
We show the results obtained by analyzing the image data of the water surface observed in the water in order to measure the wave heights distribution in a plane. We consider about the relationships between the wave heights measured by a wave meter and the brightness (AD converted values, such as R, G and B values). The light source is the natural lights.
In this paper, the flow generated around the cylinder which is at rest and rotates slowly is visualized by using the smoke.The continual time of this smoke using cigarette (Japanese short piece) is comparatively long and its white is deep.The cylinder is initially attached to a side wall (a flat plate) and detached slightly from the plate latter. The experimental results are summarized as follows, 1) Vortices stretched in a row are observed at the lower part of the front of the cylinder. 2) If the clearance between the cylinder and plate is very small, the radius of vortices is large in the case of a counterclockwise rotation compared with a clockwise one.
The vortex street model proposed by Th.v.Kirmin Is a well known mathematical model for describing the unsteady wake Induced by a columnar body advancing with uniform velocity in a still fluid. Also, the growth and decay of microperturbation generated in the wake have been studied using the linearapporoximation model of a unsteady wake, as an object of application of the stability theeorem to the field of flow. Each of the two models are made up of different numerical expression for analyses of a same wake induced by a body, nevertheless little attention has been given to the relationship between them. On the assumption a perfect fluid and two-dimensional flow in the two models, this paper is intended as an Investigation of the relationship between the two models. It was found that although the mathmatical description of the two models are different, their qualitative characteristics in terms of the field of flow are very similar.
The purpose of this study is to visualize the pedestrian flow with spacetime diagram model. In this model, the direction of walking is indicated with color and the location of pedestrian is shown on x-y plane and time is shown on Z-axis. The pedestrian behavior, which is hard to express with 2-dimentional model can be easily expressed with this model.In the computer, we construct a virtual 3D space and see the model rotating freely and interactively. We can understand the construction of pedestrian flow. We applied the model to a practical case and proved its properity.
Relative LIF (Laser-Induced Fluorescence) intensities and their temperature/pressure dependencies of ketones, aldehydes and toluene were investigated at the excitation wavelength of 248 and 266nm. LIF intensities of aldehydes were quite weak. Although the LIF intensity of toluene is very strong, it was affected by temperature and pressure severely. In contrast, both temperature and pressure dependencies of LIF intensity of acetone and diethyl ketone were quite small, especially at 266nm excitation. Taking account of boiling point (B.P.), the suitable fluorescent additive (fuel tracer) mixed with iso-octane (B.P.=99°C) and its excitation wavelength for quantitative measurement of fuel distribution in an engine are diethyl ketone (B.P.=102°C) and 266nm, respectively.
For the pulse tube refrigerators, it is difficult to understand the refrigeration phenomena in experimental approach because the gas condition in pulse tube refrigerators is high pressure and low temperature which arc fluctuating. To measure the temperature under the above condition, we adopted Planar Laser Rayleigh Scattering Method (PLRS method) using excimer laser (wavelength 193nm). It is possible to measure the gas temperature field without contact with the gas. In order to evaluate the possibility using PLRS method, we took the following basic approach. We measured the Rayleigh scattering intensity in the metal tube with quartz glass windows for several static pressure (0.1, 0.2, 0.4, 0.7MPa). The linearity error between Rayleigh scattering intensity and pressure is 15.4% in a laser shot measurement, 1.3% in the average of 10 laser shots.
A new calibration technique of liquid crystal thermometry has been introduced to the quantitative temperature measurements in a thermal flow and is applied to volumetric temperature measurements in a thermal convection experiment to investigate the three-dimensional thermal structure. It is proved that the present calibration technique improves the accuracy of temperature measurements as a factor of 2 in comparison with a clasical calibration technique with hue. The volumetric temperature measurement is carried out by scanning a light sheet and capturing a number of two-dimensional visualized thermal images. The results demonstrate a three-dimensional and cross-sectional view of the thermal plume developing into a cold fluid by buoyancy force, indicating the usefulness of this technique.
The infrared thermography near ambient conditions is proposed to estimate a temperature field of heated air jet quantitatively. We insert a wire or net into the flow field firstly, and then the temperature field is measure and visualize by observing the wire or net using an infrared camera. The true temperature distribution is finally acquired after calibrating a surface temperature of the wire or net. We also estimate the buoyant effect by increasing temperature of air jet. The measurement error is further estimated using ANSI/ASME PTC 19.1-1985 measurement uncertainty to confirm the accuracy. It is revealed from a series of experiments that the proposed technique of measuring temperature is useful to estimate the temperature field of air jet quantitatively.
Recently the unit type air-conditioning device which is a small and efficient is required in industry and public welfare. In this research an experimental device is the airconditioning device introduced into the semiconductor manufacturing facilities. The purpose of our research is improving this device small and high performance.For the purpose we paid attention to the fin-tube heat exchanger in this device. As the aircondition device is miniaturized. the heat exchanger inclines in the current of air. As a result the current of air doesn't have the same velocity distribution in the heat exchanger.In this research we thought the analysis of the influence which the inflow condition on the heat transfer performance.
Heat transfer by natural convection and radiation in participating fluids enclosed in a square enclosure is numerically simulated. The continuity, momentum and energy equations are solved by the control volume method while the radiative heat transfer is analyzed by the Monte Carlo simulation. The Monte Carlo simulation is linked with the SIMPLE algorithm for solving the Navier-Stokes equations. therefore all variables such as U, V. and T are solved each time the radiative heat flux is updated. As the result, the influences of thermal radiation on the flow and temperature fields are found significant. The radiative heat transfer is dominant. The convection is also strengthened. These features become clear with higher optical thickness.
Subcooled Pool boiling heat transfer from a horizontal wire to distilled water is experimentally studied under an atmospheric pressure condition. The horizontal cylinder is made of platinum. Diameter an length of the wire are 0.8 mm and 59.7 mm respectively. The horizontal wire is heated by a D.C. electric power source. Vaper bubbles on horizontal cylinder is photographed by a frash (25μ s) of storoboscope.
In order to obtain density variations in axisymmetrical flow field, an image-processing system for analyzing interferograms is developed. The system consists of a Mach-Zehnder interferometer, a nitrogen pulse laser, and a CCD-camera. Images are processed by personal computers. Axisymmetrical flow fields are generated by shock waves, which are dischargedfrom an open end, and observed by using the present system of the image-processing. The gas is nitrogen, the intial pressures are 49 to 196 kPa, and the incident shock Mach numbers are 1.2 to 2.0. The observed density distributions are found to be in good agreements with the CFD ones.