The vortex flows in the wake of a circular cylinder were visualized by hydrogen bubble techniques. The images of the flow past a bubble generating-wire frozen by a flashing light were consecutively exposed on a moving roll-film in a camera to save the waiting time for the next exposure. A method of image processing for the automatic measurement of the temporal velocity profiles crossing the generating-wire was developed in the digital-images of the flow captured in a micro computer. The successive data of the temporal velocity profiles were transformed into the data in space domain by use of Taylor-hypothesis, and the procedure to determine space derivative of the velocity, i.e., the velocity gradient tensor was established to investigate the kinematic structure of the vortices in the wake.

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Thermo images and heat transfer characteristics downstream of a backward-facing step were measured varying separation distances between pairs vortex generators which were set upstream of an entrance of step in order to control the heat transfer. The pair of vortex generators is made of two rectangular blades widening downstream. Addition of the longitudinal vortex which is produced by the vortex generators to the main shear layer flow separated from step entrance caused the reattachment point of main flow to move upstream, suppressed the fluctuation of reattachment flow, and the heat transfer consequently was improved in the recirculation region.

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The inertial force that acts to a two-dimensional flat plate is able to estimate rationally by considering the capacity of adhesive wake. The adhesive wake progresses to about 2.2 times of the width(B) of the flat plate and able to evaluate the process uniformly by non-dimensional number Ft. Ft--u/(B·du/dt)1/2 and u is the time dependent velocity of principal flow. In oscillatory flow, non-dimensional number Ft can express a characteristic of the wake in detail than KC number.

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Experimental study was performed to investigate flow characteristics near a shear layer in intersecting region of diverging streams in multiple diamond-shaped islands. The wake flow in intersecting region were visualized using the fluorescein dye illuminated by a laser light sheet. The velocity variations in flow field were measured using two-dimensinal laser Doppler velocimetry. It is found that the difference of flow patterns depends on the arrangement of the diamond-shaped islands, the Reynolds number and the existence of the turbulence mesh. The characteristics of velocity variations in the intersecting region are also clarified.

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The behavior of interface between a water droplet dyed red to make dear its boundary and silicone oil surface on which the droplet falls was observed by using a high speed video recorder with 500 frames per second. Eleven kinds of silicone oil whose kinetic viscosity νT is 1 mm2/s to 105 mm2/s were used as the target liquid A droplet having 3.1 mm diameter falls freely from a micropipet whose height was varied between 100 mm and 1000 mm.
The configuration of silicone oil cavity at its deepest state and that of deformed droplet at its maximum spread were classified into seven and five respectively based on their observation results. Under some conditions disintegration of droplet were observed, which accompanied remarkable deformation of oil surface at lower viscosity νT<102 mm2/s, while it occurred on the plane oil surface at higher viscosity of νT>5×103 mm2/s.

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Surface shape of a magnetic fluid droplet under homogeneous and uniform magnetic field has been discussed by several researchers. However, the deformation of a magnetic fluid droplet under non-uniform magnetic field is not clear. In this paper, behaviors of a magnetic fluid droplet under non-uniform magnetic field are studied. The surface deformation of the droplet is investigated using CCD camera before and after its impact on the solid surface. It is shown that non-uniform magnetic field breaks axisymmetry of the droplet shape. After the impact on the solid surface, the magnetic fluid droplet forms a thin disk and then several spike-like cusps appears.

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Air bubbles in liquid are one of the most important objects to be studied in many engineering fields. And they have been pictured in many occasions. But it is also well known that their boundary regions are the most difficult objects to observe, because of strong reflection and refraction.
Authors start experiments with developing techniques to observe a liquid ball. Their appearance varies not only according to their behaviors but also illuminations. In this paper, authors show several features of water balls in oil such bubble behaviors as sinking fast, neutrally buoyant, or bubble appearances as transparent, fluorescent and so on.

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Motion of bubbles and flow in a vertical cylindrical liquid column are measured applying image analysis techniques. Bubbles, which are generated sequentially at a bottom nozzle, travel upward with a regular interval, then a pair of bubbles coalesce. Characteristic quantities of bubbles are measured from video pictures, which are taken with a homogeneous illumination from behind. Motions of the bubbles are measured from same pictures using PTV. Flows are visualized using dispersed small particles illuminated by a light-sheet, and velocity distributions are measured using PIV. The Reynolds number based on a bubble diameter is 0.8 to 1.5 with a diameter ratio to the experimental pipe being 0.25.

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Ignition and combustion processes in a prechamber combustor by a flame jet are experimentally investigated using schlieren photography. The effects of the nozzle diameter on the structure of flame jet, ignition process, and subsequent combustion process in the main chamber are examined by combining schlieren observations and main chamber pressure histories. The structure of flame jet is found to be greatly influenced by the nozzle diameter, and can be classified into four types; a high speed jet of hot combustion products without flame kernels, one including a small amount of flame kernels and rich active species, a relatively high speed jet containing with flame kernels, and a low speed flame column. Depending on these flame jet properties, the ignition and combustion processes in the main chamber are also divided into four types; extinction of a flame jet, extremely rapid explosion after a long ignition delay time, relatively rapid turbulent combustion with fine wrinkles, and spherically propagating slow wrinkled laminar combustion.

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It is well-known that turbulent wake flow behind the grating which consists of fine cylindrical rods has many eddies with a uniform scale particular to the rod diameter, and exhibits a dominant peak in the frequency spectrum of the velocity fluctuation. In this investigation the behavior of the turbulent premixed flame propagating in such a intense turbulent wake flow without mean, which is produced by a high speed motion of the grating of about lOm/s in stagnant premixed gas, are optically examined using tomography technique. It is first shown that, in the case without motion of the grating, a smooth and spherically-propagating laminar flame is observed in the stagnant mixture. In the intense turbulent wake flow without combustion, many eddies with a uniform scale are clearly distinguished, and a corrugated flame front propagating radially is clearly observed in the case with combustion. Keywords: Combustion, Turbulent Premixed Flame, Flame Structure, Tomography Diagnostics, Fine and Intense Turbulence

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Interaction of a strong vortex ring with a premixed flame was experimentally studied in order to understand how the flame is affected by an element of intensive turbulence. The interaction of a vortex ring with a flame in our experiments could be observed by six sequential schlieren pictures, OH-LIPF and CH-LIF images. As a result, Two types of interacting behavior have been observed in our experiments, i.e., Type 1 and Type 2.

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Combustion with highly preheated and low oxygen concentration air is utilized for development of high performance industrial furnace. And this combustion have been researched by various method. This paper describes visualized analysis of the flame properties in the furnace which can generate highly preheated and low oxygen concentration air. By a high speed UV video camera and a CCD camera, we measured the spatial distributions of emissions from radical species in the flame under three conditions which were different in terms of preheated temperature and oxygen concentration, and calculated the spatial distributions of fluctuation and vibrational temperature. Flame fluctuation was calculated by Fourier transform, and vibrational temperature was calculated from emission intensity distributions, based on the Boltzmann distribution low. In addition, temperature distributions in the furnace were also measured by thermocouples. As a result, it is indicated that preheating air can stabilize the flame and diluting oxygen concentration can uniform the flame temperature.

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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 were recorded by two-frame CCD camera with dual YAG Laser. The analysis of the diesel spray velocity vectors were conducted using PIV analyzer with cross-correlation method. The PIV results show the three-dimensional spray patterns of the VON in the part load range.

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Abstract : This study deals with aerodynamics phenomena in the wake of a flameholder in a high speed air flow. The Particle Image Velocimetry (PIV) technique has been used to get the velocity fields. The flameholder has a simple V-gutter shape and allows the injection of fuel gas by a pipe with a row of small holes. We observed in the high speed air flow the same kind of phenomena as in the water flow : some vortices are shed alternately from either edge of the flameholder. But in the air flow, some small vortexes appear on the outline of the main eddies as a result of much greater Reynolds number. When the fuel gas is injected, the flow pattern changes drastically and the vortex shedding doesn't occur anymore. A mixing zone between fuel and air appears in the wake of the flameholder. The better understanding of the mixing process resulting from this study should be useful for the design of the ram combustor.

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Anumerical study is performed on control of jet attachment by parallel controlling jet in asymmetric channel. The analysis of this study was carried out for the several combination models in the width of controlling jet nozzle over a wide range of the flow rate ratio between main jet and controlling jet. The k-ε turbulence model was chosen to calculate the velocity The results obtained were as follows; the attachment distance of jet was increase with increasing flow ratio and flow direction changed discontinuously, and attachment distance decreased in high flow rate ratio.region with increasing flow ratio. The switch of flow direction occurred less flow rate ratio by extended controlling nozzle.

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The mixing, diffusion or absorption of a gas into a liquid is used widely in various kinds of industries. In this study, a small oscillatory jet type gas-liquid reactor is proposed and its oscillatory and flow characteristics are made clear using flow visualization and image processing techniques.

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This paper is concerned with the cooling unit which applies the flow mechanism of fluidics called the vortex chamber oscillation device. The water jet issuing from this cooling device impinges on the heated plate with swinging by itself. The flow aspect in the cooling device and the impinging patterns of the water jet have been studied by means of the high speed digital video camera and the image processing system. As a result, the oscillating period is estimated by the sequential frames from this camera. The large scale vortex is recognized from the vector diagram obtained by the PIV system. Explanation about the oscillating mechanism has been tried by using this large vortex. Moreover, the cooling process by this device is also visualized by using the temperature-sensitive liquid crystal film. The effects and the strong point of this cooling device have been discussed.

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To investigate the unsteady structure of secondary flow of a turbulent bounded jet in both Fourier and physical spaces, the wavelet auto-correlation analysis was used to analyze the fluctuating velocities at various positions in a bounded jet. The wavelet auto-correlation analysis provides the auto-correlation characteristics of signals in terms of period and time delay. From the wavelet auto-correlation analysis, the branching structures in WR(a, τ) reveal that a periodic large eddy motion contains the periodic small eddy motions. In the shear layer near the wall at x/b₀=8, y/b₀=1 and z/b₀=1.87, the wavelet Auto-correlation analysis may determine the period and the location of the large-scale structure and the secondary flows.

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In order to reveal structure of secondary flow of a turbulent bounded jet in terms of period and time delay, the wavelet cross-correlation analysis was employed to analyze cross-correlation relationships between xcomponents of the fluctuation velocities at two different points near the wall in the near field. From the distributions of the wavelet cross-correlation coefficients, similar structures of eddy motions with various scales were shown and branching of eddy structures was observed. The period of eddy can be easily determined in terms of period and time delay.

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The aerodynamic interference between two circular cylinders in a tandem arrangement has been examined over the Reynolds number range 10⁵to 5 × 10⁵. The static pressure distributions around the circumference of each cylinder were measured and the drag and lift forces were obtained for each cylinder. Over a small range of Reynolds number at the critical regime, a laminar separation bubble is formed on one side only of the upstream cylinder and both cylinders experience the lift forces. The Reynolds number range where a bubble is formed on one side only of the upstream cylinder becomes large with decrease of the spacing between two cylinders.

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Today, high class swimming race is competed in the range of 1/100 second. It is important to develop a swimming suit with low drag. This paper describes the relationship between fluid drag and flow pattern around body. The experiment is carried out in water channel by using a woman's artificial model. The model set under the carriage is pulled from 0.75 m/s to 2.02 m/s in water channel. The drag by the difference of water depth and velocity in swimming is explained by flow visualization around the model. Also the drag by the difference of swimming suit in swimming is explained by flow visualization around breast.

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The purpose of this study is to clarify the influence of interaction between deformable surface and flow field. Generally speaking, Dolphin could swim fast because of oscillated stomach skin. Cylinder models having an elasto-flexible surface were used to simulate the skin of marine animal. These cylinders were placed in water tunnel, and using laser light sheet method to visualize deformation of its cross sectional form, pattern of vortex shedding from the model, flow separation point. Vorticity and hydrodynamical forces were measured. As a result, three different patterns of travelling wave generation on the surface of elasto-flexible cylinder were observed. Separation points moved to downward more compared with the rigid one. And streak line in the vicinity of the wave is broken by new generated wave and small vortexes shed simultaneously from the surface. Distribution of vorticity around the cylinder was clearly different from that of the rigid one. The cylinder, on which travelling waves appear on the surface, has shown about 10% smaller hydrodynamical drag than the rigid cylinder.

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Three dimensional separated flow visualization over axisymmetric paraboloid is conducted using smoke method. Laser light sheet is used for visualizing the detailed structure of the vortices in cross-sectional flow. The variations of streamwise vortices in each section of the body are visualized. Then three dimensional images around the body are obtained by reconstructing a series of cross-sectional images.

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Limiting streamlines on blades of a highly skewed controllable pitch propeller (HSCPP) model (MP.NO. 94-1) are visualized by the oil film method over wide operating conditions including reverse pitch angle. Experiments are carried out at the circulating water channel. Observations were done at advance ratio J=0.0, =0.4, 0.6 and 0.8 at design pitch angle (θ=0 degree), and J=-0.2, 0.0, 0.2 and 0.4 at near zero pitch angle (θ=-20 degree) and full reverse pitch angle (θ=-40 degree). The Model propeller diameter is 250 mm, and Reynold's number was around 4.6×10⁵ to 6.1×10⁵. No serious stall nor turbulent separation was observed in the experiments. Therefore, it can be concluded that for HSCPP the boundary layer assumption is approved as well for conventional CPP even at off-design conditions.

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The results of a smoke tunnel flow visualization study are presented for a non-cambered symmetric laminar airfoil NACA 631A012 with and without the miniature trailing-edge flap. The flap height and the angle of attack are changed in winder range than in the previous investigations. The smoke line patterns along the airfoil are significantly changed in terms of the variation of flap height. Flow around the specially designed complex airfoil is also investigated.

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An visualizing investigation of vortex flow structure on thin delta wings with apex fence ( Fence is attached at angles of 90 and 135 degrees. ) is presented. Smoke flow visualization and the light sheet technique are being used to obtain cross sectional views of the leading-edge vortices. Total pressure distribution is measured by traversing total-pressure rake and visualized by computer graphics. A combination of total-pressure distribution maps and lateral cross sectional views provides information on the three dimensional nature of the vortex structure induced apex fence.

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This paper describes both the flow field around an airfoil and the aerodynamical properties of the airfoil subjected to the ground effect. The Reynolds number was 1.2×10⁴. Our attention was primarily focussed on pressure measurement on a ground plate. Some specific features of the pressure distribution were clarified. We attempted to evaluate lift acting on the airfoil by performing surface integral of the pressure on the ground. Two types of end plates were tested as a preliminary experiment. The results obtained were anticipated: the pressure tends to become higher as an end plate has such shape as to decrease the spanwise velocity component over the airfoil. The results of the measured pressure distribution were found, in general, to reflect strongly enough the features of the flow field visualized by the smoke wire method.

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Particle tracking velocimetry (PTV) is one of the methods to measure flow velocity fields which is considered to be essential and useful for analyzing complex flow fields. This paper proposes a temporally particle pairing method using genetic algorithms and a flow velocity field estimation method using neural networks. The particle pairing method is based on spatial pattern relationship between pair-candidate particles with their respective neighbour particles in two exposures taken over a small time interval. If two particles are paired correctly, the spatial patterns of their pair-candidate particles are to be similar. The method finds correct pairs by applying a genetic algorithm. A potential problem of the method is that it can't measure velocity vectors at the points where no particles exist. The flow velocity field estimation method proposed in this paper solves it, which uses neural networks. The neural network is trained by using measured velocity vectors as teaching data so that the derivatives of a certain scholar function agree well with the measured data. The continuity equation of flow is consequently satisfied in the estimated vector fields and the scholar function gives the stream function.

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With extremely improving computer performances, computer aided visualizations of numerically calculated data are strongly needed to be realized in easier operation and lower cost performance. This paper describes a newly constructed software for 3D computer graphics including animations of numerical calculation data. Several examples are clearly visualized using the present 3D animation software, which can well verify its usefulness and wide applicability.

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The purposes of this research are to analyze and visualize some properties of aesthetic surfaces and to construct the shapes, which satisfy designers' intentions. To extract and visualize the properties, surface edges of a free-form surface were introduced. The edges are loci of the points that have the extremum values for characteristics of the surfaces such as curvature, height, brightness and so on. By analyzing idea sketches drawn by styling designers, we find that the designers' intentions are closely related to the contour curves and the surface edges. The results of this research give fundamental technology not only to classify features of free-form surfaces but also to generate an aesthetic shape according to the styling designers' feelings.

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Ultrasonic CT has been applied to visualize the temperature field as a kind of nonintrusive method. This research tries to develop a new ultrasonic CT reoonstruction method based on inverse matrix transfer which differs itself from the ordinary CT reconstruction, known as FBP(Filtered Back Projection) with SL Filter, in the way of dealing with problems such as having not enough projection data due to limited projected angle. In current paper, 3 kinds of iterative CF reoonstruction algorithm are described. Computer simulations are oonducted to verify the above algorithm and the reoonstruction results are oompared. According to the simulation results, CGM (Conjugate Gradient Method) is confimied to be the most optimum iterative way and find will find its use in our further experimental stage.

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In this paper, we will propose a unified approach to ray tracing scattering colors of transparent optical systems. To attain that end, we will first present system theoretical modeling of transparent layered optical systems to obtain an efficient algorithm for computation of their total reflectivirie and transmittivities. Then, with the aid of these preparations, we will develope a new ray tracer to visualize wave optical scattering phenomena of a nested system of transparent objects coated with transparent thin layered media, such as dispersion colors of prisms, interference colors of soap bubbles and Newton rings, as well as optical tunnel effects and resonance scattering.

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In this study, a method for two-dimensional temperature measurement based on 02-LIPF (laser-induced predissociative fluorescence) using a broad band ArF excimer laser is proposed. In this method, temperature is measured by use of temperature dependence of ratios between fluorescence intensities integrated in two spectral region including peaks. To reduce the measurement time and improve the measurement accuracy, we develop a stereo-viewer which can put two images passed through two different filters on a picture frame. This method is applied to heated air jet, and radial temperature profile at x/D=6 (x: distance from nozzle; D: nozzle diameter) is compared with that obtained with a thermocouple. Two-dimensional temperature image of the jet is also measured successfully.

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The breakup process of a liquid drop plays an important role in the various engineering problems such as the gas atomization for the production of fine metal power, the ink jet printer and the fuel injector of the Diesel engine. The detailed mechanism of the breakup of liquid drops, however, is not well understood. In the present research, the diagnostic system based on the inline laser holography is constructed to clarify this process. This method determines the size and location of a small particle by comparing the hologram pattern obtained by the experiments with that by the theory. The method is proposed that uses the ultraviolet laser as a light source of the holography system. The distance between the target particles and the hologram plane can be made longer by using the light with a shorter wavelength. This will give a particular advantage to the practical applications in avoiding the holographic film or the lens system being wet by the droplets.

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An optically accessible small DI diesel engine has been developed, which enable the shadowgraph observation with an elongated piston under high speed and heavy load conditions. The tolerable maximum engine speed and in-cylinder pressure are 4000rpm and 12MPa, respectively. The key techniques of this engine are sapphire window, ceramic coated upper piston and seamless resin oil-scraper-rings. The sapphire window decreases the weight of the elongated piston while keeping the enough strength. The ceramic coating realizes non-lubricating operation for the upper piston. The seamless resin ring prevents the lube oil in the crank case from dispersing on the optical mirrors.

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Using a novel optical system, simultaneous imaging of schlieren photography and laser induced predisociation fluorescence of OH radicals (OH-LIPF) have been carried out to examine combustion processes and flame structure in a two-dimensional and vertical type valveless pulse combuster. The combuster is fueled by propane/air mixture and operated at a pulsation frequency of f0=137.5Hz. The planar OH-LIPF imaging optical system used is composed of a tunable excimer laser tuned to a wavelength of 248.5nm and an image-intensified CCD camera system to detect the LIPF image at a wavelength of 308nm. According to the simultaneous imaging of shadowgraphs and OH-LIPF, it is found that OH-radicals never disappear in the combustion chamber during a period of pulsation, and that the intermittent ignition is due to the combined effects of the thermal and chain-reaction processes in the residual hot combustion products in the last cycle.

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We have proposed the paint erosion method for non-contact measurement of wall shear stress distribution. The basic principle of this method is based on the assumption that erosion of paint on the wall is mainly caused by wall shear stress. Therefore, wall shear stress is estimated by detecting the decrease in paint thickness which is measured by light transmission power instantaneously using image. The relationship between wall shear stress and decreasing rate of paint thickness was clarified with steady and unsteady flow in a pipe flow. The Reynolds number was set in ranged from 885 to 14147 in steady flow to examine under laminar flow and turbulent flow condition. Frequency of unsteady flow was set 0.67, 1, and 1.13 Hz to observe influence of pulsatile flow to the erosion speed. The velocity profiles of each flow were measured by laser dopplar velocimetry. A definite correlation between wall shear stress and decreasing rate of paint thickness existed independently of the flow pattern, initial thickness, an pattern of the paint. We concluded that the paint erosion method has great potential to measure the wall shear stress without probe.

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We propose a procedure to compose a image based on Taylor hypothesis from the video pictures of streak lines visualized by the electrolysis method in the wake of a circular cylinder. The Taylor-hypothesis images are intimately related to the vorticity distribution since the streak lines were visualized by dye issuing from the surface of the cylinder, i.e., the generation surface of the vorticity. In order to clarify the relation between the Taylor hypothesis image and vorticity distribution, the vorticity distribution based on Taylor hypothesis was obtained from the time series data of the velocity past a bubble-generating wire determined by hydrogen bubble techniques. Some misleadings of the vortex structure in interpreting the patterns of streak lines were reviewed.

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This paper describes an experimental investigation on unsteady thermal convection flow in a horizontal closed-duct combined with acoustic standing wave induced in the duct. As the amplitude of acoustic standing wave increases, steady circulating streaming caused by nonlinear effect of finite amplitude oscillatory flow appears within every 1/4 wavelength section. It is called acoustic streaming. On the other hand, the thermal convection flow is characterized by Rayleigh number. In the range of high Rayleigh number, the convection current changes to unsteady and turbulent. When a strong acoustic standing wave is combined to the unsteady or turbulent convection flow, the flow pattern of the convection quickly changes to steady circulating flow similar to the acoustic streaming. PIV technique is applied to quantitative analyses of the resultant flow depending on mode of standing wave, sound pressure, and Rayleigh number. The results show that the resultant flow becomes unstable according to increase of Rayleigh number and at lower mode of oscillation.

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Experimental investigations on pressure fluctuations generated in a flow through a circular pipe with an axi-symmetric cavity at high Reynolds number are described in this paper. Flow patterns in the cavity are visualized by illumination with laser-light-sheet, and recorded by using a still camera and a high speed CCD camera. Pressure fluctuations generated, in the cavity are measured by pressure transducer, and analyzed by FFT. The visualization results show that the fundamental feature of the flow in the cavity depends on the ratio of cavity depth (h) and length (L), a stationary ring vortex is produced in the axi-symmetric cavity in the case of h/L=1, and according as decrease of the ration the vortex developed at up-steam side moves toward down-stream side and is emitted to main stream. The results of frequency spectrum obtained by FFT analyses on pressure fluctuation in the cavity show that the peak indicating the fluctuation becomes discrete and higher as the value of h/L decreases.

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This paper describes about the flow and temperature visualization in a partially divided vessel by thermosensitive liquid crystal suspension. Partitions were set vertically on the bottom heated plate. Scattered light from the liquid crystal" suspension was transformed by using regression equation of relative brightness (r, g, b). A partition controls the behavior of thermal plumes from heated section. It is supposed that the thermal diffusion is enhanced by changing the material. Effect of a partition was also examined on the rising velocity and the frequency of thermal plumes.

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The characteristics of the supply air flow from an air-conditioner affect to the room flow distribution. Heated air which Archimedes number is equivalent to an air-conditioner was supplied to chamber modeled of real resident space. The velocity in the flow of the model was analyzed by Particle Image Velocimetry(PIV). It became clear that the flow rose and never reached to floor in case of Archimedes number is larger than 0.02.

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Dust mobilization in a vacuum vessel (VV) of a fusion reactor during a loss-of-vacuum accident (LOVA) was studied numerically and experimentally from a viewpoint of the fusion safety research. After the LOVA occurred, air flows from the outside of the VV through a breach into the inside and the activated dust is blown up from the walls inside the VV, and then it can be considered that the dust is conveyed due to a buoyancy flow to the outside of the VV through the breach. The velocity, pressure and temperature distributions were obtained by the present numerical analyses and the dust mobilization behavior was predicted quantitatively. In addition, the dust transport characteristics from the inside of the VV through the breach to the outside due to the buoyancy effect was clarified by the visualization experiments.

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For reduction of dioxins in MSW (Municipal Solid Waste) incinerators, complete combustion by thorough mixing of combustion gas with oxygen supplied as primary and secondary air is important. So far we have realized a very low dioxins level with our unique mixing concept. However, as it is getting required to reduce dioxins concentration to further lower level, another effort had to be made to give a furnace configuration and air supply enabling better gas mixing.
In evaluating the gas flow in a furnace, CFD (Computer Fluid Dynamics) and/or flow visualization in a miniature are generally used. However, both approaches have such problems that the former could not give a precise turbulent pattern and the latter gives only qualitative solutions. Applying PTV (Particle Tracking Velocimetry) method to flow visualization, we found mean turbulence intensity in the mixing zone useful as a quantitative mixing indicator. By employing the indicator we have determined a furnace configuration including air injection which enables much enhanced gas mixing.

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When a solitary wave is running up to a slope (15°) obliquely at an angle of 30° to a shore line we can record the side view of this runup phenomenon on videotape by illuminating the water surface with a laser light sheet. The water has been mixed with the fluorescence. A solitary wave transforms while propagating to the slope. We get the wave profile by image processing the recorded images. Between these wave profile images we can calculate the cross correlation and decide the beginning point of transformation and know how the wave transforms and loses the symmetry.

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In this paper we calculate the two-particle diffusion in stationary homogeneous isotropic turbulence by direct numerical simulation (DNS). Using the second invariant of velocity gradient we visualize the turbulent structures. The two-particle diffusion of intermediate time is affected by those structures, so we refer to it as the structural diffusion. We indicate that the straining region plays an important role of the structural diffusion.

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Measurement of three-dimensional density distributions in a transient unstable stratified flow is important for the safety analysis on the advanced type nuclear power plant. Three-dimensional density distribution can be reconstructed using computer tomography technique from interferogram images. However, in the experiment, only a few interferogram images could be taken. Conventional tomography techniques have low accuracy with the limited interferogram images, since the information of the projection is not enough for the reconstruction. While, the transient interferogram images can be easily taken using the real-time holographic interferometer and/or Mach-Zehnder interferometer. That is, there are enough information for the temporal domain. In this study, a transient three-dimensional (4D) reconstruction technique was proposed. The four-dimensional density distribution was assumed to be expressed as the summation of Elementary Distribution Functions (EDFs). The EDFs were distributed not only in the spatial domain, but also in the temporal domain. The tomography was carried out as the optimization of the arrangement for EDFs, using the temporal projection information.

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