Blowing snow is highly significant for both engineering and climatological reasons. In this presentation, firstly, a systematic measurement of blowing snow conducted at Mizuho station, Antarctica is introduced. A blowing snow observation system including snow particle counters (SPC) which can sense not only the number of snow particles but also their diameters, was situated on a 30 m tower. All instruments worked properly and the data obtained revealed profiles of mass flux and particle size distributions as a function of the friction velocity. Measurements were compared with the computations by means of a numerical blowing snow model which incorporated aerodynamic entrainment, grain/bed collision, wind modification, particle size distribution and turbulent fluctuations on the particle trajectories.

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R&D study of Mitsubishi Regional Jet (MRJ) has been conducted since 2003, under the auspice from NEDO. In this study, various fundamental research items for aircraft development including advanced aerodynamics, noise study and multidisciplinary design optimization (MDO) have applied to the design of MRJ. In these R&D activities, state-of-the-art technology developments have been pursued by strong university-government-industry cooperation. This report presents application of CFD and MDO technologies to MRJ design as an example of R&D activities.

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The amplification rate of azimuthal waves of a vortex ring due to the Widnall instability is reduced by means of the axial flow along a vortex core called a "swirl", so that the vortex ring with swirl increases its movable distance. On the other hand, it leaves a part of circulation with its fluid particles in helical shape on the path just after the formation stage. A successive 3-D flow visualization images are reconstructed from a stack of parallel imaged planes obtained by using the laser scanning technique for the purpose to investigate the complicated 3-D structure of vortices. And we examine the early stage of a vortex ring with swirl and helical streak structures which are the main cause of the circulation decrease.

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In the application of vortex rings for material transportation, the collapse of the ring structure resulting from the Widnall instability of a vortex ring decreases its movable distance. The axial flow along a vortex ring core called a "swirl" is numerically superimposed on the normal vortex ring in order to reduce the amplification rate of circumferential waves, and the appearances of vortex structures are observed by means of the iso-vorticity surface. Independent of the thickness of a vortex core, the movable distance of the ring increases once with the axial flow rate enhancement, and then decreases. In addition, the effective factors determining the movable distance are discussed.

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An air jet, which remains laminar and axisymmetric in the single-phase flow, is simulated in the particle-laden condition. The vortex method proposed by the authors is employed. An air issues with velocity U_0 from a nozzle into the air co-flowing with velocity U_a. The Reynolds number based on U_0 is 1333, the velocity ratio U_a/U_0 is 0.4. Glass particles with diameter 65μm are loaded at the mass loading ratio 0.025. The particles impose disturbances on the air and induce the three-dimensional flow, resulting in the transition from the axisymmetric flow to the non-axisymmetric one. As the particles make the air velocity fluctuation increase, the air momentum diffuses more in the radial direction, and accordingly the spread of the jet becomes larger. The abovementioned results agree well with the trend of the existing experiments. The vortex method can capture the flow transition caused by the particles laden on an axisymmetric air jet.

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Turbulence characteristics in the spatially developing turbulent plane jet with scalar transport is investigated by means of the direct numerical simulation (DNS). The Reynolds number based on the slit width d and exit mean velocity U_J, Re_d=U_Jd/ν, is 1,500. DNS results are in good agreement with the previous experiments. The coherent structure of plane jet is visualized.

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A hand dryer, used to dry wet hands with high-speed jets, has the conventional nozzles that spout in the fixed direction. Because the jets from those nozzles can't reach all area of hands, some water remains partially and the drying time becomes longer. To shorten the drying time, we have studied the reciprocated jet that removes the water on hands effectively. The behavior of the water separation was observed by high speed camera, and the mechanism of water removal was modeled. As a result, the developed product improves the drying time from 8 seconds of the previous product to 3 seconds.

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This study was focused on the nature of fluctuation in an atmospheric microwave plasma jet. The plasma jet is issued into the ambient air. Two kinds gases were used : nitrogen and argon. It was clarified that the detailed behavior of the plasma jet is mainly dependent on the gas being used, and also observed that the argon plasma jet heaves for large flow rate although the nitrogen plasma jet has no fluctuation. The heaving frequency increases approximately linearly with gas flow rate. Moreover, the velocity measurement of gas flow with no microwave supply was conducted by PIV, then the each velocity field is remarkably different for Q=2 1/min by the difference in density of the gases.

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This study investigates active control of self-sustained oscillating flow past an open cavity by using suction and blowing. The incompressible Navier-Stokes equations are solved for the two-dimensional cavity with laminar boundary layer upstream. We use suction and blowing with the velocity ranging from 0.05 to 0.1 and the angle ranging from 15 degrees to 90 degrees. It is found that the effect of suction and blowing changes the characteristics of recalculating flow in the cavity. When the suction and blowing velocity is 0.1 and the angle is 45 degrees, a clockwise recalculating flow exists in the cavity, then the self-excited oscillation is completely suppressed.

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Jets diffusion were controlled by the film flow which was given acoustic excitation. First, the preferred mode frequency of a jet was measured by the hot wire anemometry to investigate the excitation frequency. A change of the potential core was analyzed by visualization and velocity measurement by LDV. For the mainstream, Air, CO_2, and He were used. Momentum ratio of a jet to the air film flow was changed MR=Mf/Mm=0.1〜1.0, and a suitable velocity fluctuation was given to a film flow by the acoustic excitation. Those effects change the average velocity distribution and turbulence on the central axis. These show the detailed relationship of the diffusion effect by the acoustic excitation and suppression effect by the film flow.

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In this study, to promote the jet diffusion is mixed to give a lot of confusion on the basis of the frequency of the preferred frequency occur early region jet column mode. First, the variation of velocity of a jet was measured by the hot wire anemometry to investigate the preferred frequency. The preferred frequency was the result of the FFT analysis of the variation of velocity. For the jet, Air, CO_2, and He were used. Next, to visualize a cross section of vortex ring to use the Laser Light Sheet Technique. These show the detailed the relationship between jet density and diffusion.

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This experimental study aims at measuring concentration of jet diffusion. Hot-wire concentration sensor to measure the concentration of the components in a binary mixture of gases is described. The concentration sensor consists of a concentration probe, a vacuum pump, a hot-wire amplifier. And the concentration probe consists of a brass sonic nozzle, a brass tube, a tungsten hot-wire to measure gas thermal conductivity of gas mixture. There are two main parameter in King's equation which are velocity and thermal conductivity. The sonic nozzle decreases the effect of velocity. The new probe calibrated with helium jet. The calibration curve was made with helium-air mixture. And the time constant was 0.9 ms. Contour of velocity and concentration of helium jet diffusion was measured.

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Effect of density difference on dynamic behavior of swirling jets has been experimentally investigated in this work. When the density of inner jet is heavier than that of outer jet, stagnating flow becomes easier to be formed compared with that of iso-density flow, similarly to that reported in our previous work[3]. The location of stagnation point is lower than that of iso-density flow, which is clearly shown by velocity profile along the centerline of inner burner tube.

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In order to improve the heat transfer on the wall, impinging jets is used in various industrial applications, and has been investigated experimentally and numerically so far. However, it is not enough to make clear the detail of vortical structure contributing to the heat transfer. In the present paper, DNS (direct numerical simulation) of the impinging jet is conducted to investigate the heat transfer through the nozzle vector control. The discretization in space are performed with hybrid scheme in which Fourier spectral and 6th order compact scheme are adopted. From instantaneou view of flow structures, it is found that the vortex structure is changed significantly on the wall. In addition, From the statistical it is found that flow properties and the heat transfer are improved using the vector control.

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In order to develop a new mixing procedure, we conduct DNS (direct numerical simulation) of vector control for free jet. The nozzle is periodically oscillated by vector control. From view of instaneous vortex structures, it is found that the structures are modulate, compared with the case of the free jet. In contours of ensemble averaged streamwise velocity and turbulence kinetic energy, the jet diffuses largely in the oscillating direction. While, the jet shrinks in the perpendicular to this direction. As a result, the vector control can be expected for the improvement of mixing efficiency.

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Vortex generator can produce a turbulence and longitudinal vortices and control the separation point on the tube surface, and then augment an impinging area of the flow on the fin surface. In order to determine the best configuration of vortex generator, it is necessary to know the effects of vortex generator on the flow and heat transfer characteristics over the tube and fin surface. In this study, we used louver-type vortex generator and tried to find out the effect of vortex generator on the flow and heat transfer characteristics. As a result, using a vortex generator, the separation point on the tube moved to downstream up to 130° from the front stagnation point and the dead water region was decreased. Then, the heat transfer characteristics behind the cylinder were improved significantly. The mean Nusselt number on the tube with vortex generator was increased up to maximum 57% than the plane fin.

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The fluid force on a sphere with dimples has been investigated in Reynolds number range from 0.4×10^5 to 1.7×10^5. Two spheres of diameter 42.6 and 100mm were studied with 328 dimples on their surfaces. In the present study, the dimples in the form of circular are were used. The depth ratio of dimple (k/d)(k:the depth of dimple, d:the diameter of sphere) was changed from 0.0079 to 0.0188. The drag on a sphere with dimples was measured using a three components load cell with a strain gage. The pressure distribution around a sphere with dimples was measured using a semiconductor pressure transducer. The velocity distribution near the sphere surface was measured using a hot wire probe. From these results, the relation between the drag and the flow pattern around a sphere with dimples became clear.

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This paper reports on numerical simulations of the flow around an accelerating circular cylinder by means of Large Eddy Simulation in a noninertial boundary fitted coordinate system. Simulations with different acceleration patterns were performed. twin vortex was observed in the cylinder wake during acceleration for all the cases. This twin voltex is not obserrved for the corresponding Reynolds numbers under the steady state without acceleration Time evolution of drag coefficient is different from that predicted by the quasi-steady assumption. Under a high acceleration, the drag coefficient shows a time evolution similar to the coefficient predicted by added mass, which is not the case when the cylinder acceleration is relatively low.

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The aim of this study is to investigate on vortex behavior behind a circular cylinder by introducing jet with dielectric barrier discharge (DBD) plasma. The electrode of DBD plasma was mounted on the circular cylinder. A constant AC wave with voltage of 2kV and frequency of 10kHz is applied to the electrode. The forward and backward jets to the main flow direction were induced by electrode arrangements. The flow behavior behind a circular cylinder is visualized by a high speed video camera at Reynolds number of 1.0×10^3. We discussed on the wake and vortex behavior with forward and backward jets by DBD plasma.

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This paper describes a work of practical application of an advanced vortex method for the moving and deforming boundary problems. In this study, a fully coupled methodology is developed for calculation of moving and deforming boundary problems including the flow-structure interaction problems. In order to confirm the applicability of our code, flow simulations around a sprinter and a flexible cantilever circular cylinder were performed. As results of the present study, vortical and unsteady flow features around a sprinter and a flexible cantilever circular cylinder are understood, and unsteady variation of fluid forces corresponding to deformation of body configuration due to the motion are calculated. From the results of the present study, it has been confirmed that the vortex method is available and useful for research of the moving and deforming boundary problems.

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Periodic vortex shedding behind a circular cylinder is investigated by the DSMC method with an improved new collision scheme. The new collision scheme (U-system 3) that can deal with large cell dimensions conserves the total energy of each collision pair precisely during an intermolecular collision and the stability of the scheme improves furthermore. The lock-in phenomena in which a frequency of vortex production is synchronized with the frequency of the cylinder vibration are confirmed in the DSMC calculation.

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An array of usual blunt bodies placed in uniform flow may generate a considerable level of SPL under limited, narrow flow conditions. The sound emission is strongly connected with the interaction of vortices generated and the solid wall downstream. A fairing in the leading edge of blunt body might lead to an unexpected generation of sound.

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To investigate the dynamic behavior of vortex shedding from a discoid airfoil, which simulates a hand of swimmer, we made an experiment using a wind tunnel. The structure of flow under the pitching motion is measured by particle image velocimetry (PIV). It was cleared that the reduced frequency and the amplitude of pitching motion affect the flow structure. The amplitude of pitching motion gave more prominent effect on the velocity profiles near the back surface of airfoil rather than the reduced frequency. It was shown that the generation of vortices was dependent on the reduced frequency and the growth of vortices was dependent on the amplitude of pitching motion. In addition, it was shown the existence of the suitable range of the reduced frequency and the amplitude for the growth of vortices.

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In recent years, the flow field around moving elastic airfoil has attracted significant attentions. A flow around an elastic body is treated as a coupled problem of a fluid and a structure and it has been studied mainly by numerical analyses so far. The purpose of the present study is to perform the fluid-structure interaction analysis using ANSYS 11.0 and ANSYS CFX 11.0 and is to clarify the wake structure and characteristics of dynamic thrust. The clear thrust producing vortex street is formed in the wake of the heaving airfoils. The dynamic thrusts acting on heaving airfoils are strongly dependent on the Strouhal number based on the trailing edge amplitude regardless of elastic deformations.

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Many studies on unsteady flow at low Reynolds number regions have been carried out with experimental and numerical approaches. Especially, the flow field behind unsteady airfoil has attracted significant attentions in bio-hydrodynamics for the need to understand the propulsion mechanisms of aquatic animals, birds and insects in recent years. Moreover, Micro-Air-Vehicle (MAV) and micro flight robots with these mechanisms are also being developed actively. We have visualized detailed wake structures behind rigid and elastic unsteady airfoils using PIV measurements. However, impacts of elasticity on a flow field and differences from a flow field in the wake of a rigid airfoil have not been clarified yet. The purpose of the present study is to clarify the detailed vortex flow structure near the wall of the heaving airfoil, NACA0010. The vortex flow developed near the wall of the heaving airfoil was clarified using particular airfoil with some pinholes.

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In recent years, small flap flying objects and Micro Air Vehicle (MAV) are developed actively at home and abroad. Until now, a number of researchers have attempted to develop small flap flying objects and MAV with various actuators and devices however they have not reached practical use at the present time. One of the reasons is that flying mechanism of insects has not been clarified sufficiently. It is well known that a butterfly combines flapping motion of its wing with gliding to fly and the figure of flying is very beautiful. However, the details of flying mechanism have not been understood sufficiently. In this study, the vortex flow structure developed on the butterfly wing has been clarified by using PIV measurement.

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Many studies on unsteady flow at low Reynolds number regions have been carried out with experimental and numerical approaches. The flow field around an elastic body has attracted significant attentions in recent years. A flow around an elastic body is treated as a coupled problem of a fluid and a structure and it has been studied mainly by numerical analyses so far. The purpose of the present study is to clarify the characteristics of dynamic thrust acting on an unsteady elastic airfoil, NACA0010, with pitching and heaving motions. The dynamic thrusts acting on the rigid and elastic airfoils are strongly dependent on the Strouhal number based on the trailing edge amplitude regardless of elastic deformations. However, the thrust efficiency of the elastic airfoil is higher than that of the rigid airfoil.

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As a first step of the study on the diffusion control and the direction control of the jet, the basic characteristics of the jet flows, issuing from the pentagonal duct and the circular pipe, were investigated experimentally. The velocity distributions of the jet flow have been investigated using the hot wire sensor and the CTA system. By using the velocity distribution, the velocity decays, the half value widths of the jet and the turbulent intensities have been obtained. As a result, it has been found that there exists the difference of the flow structure between the pentagonal jet and the circular one.

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We study the influence of the flow induced by a plasma actuator on the wing-tip vortex generation. A wing model with the plasma actuator is set inside the wind tunnel and the velocity components are measured by using a PIV system. The plasma actuator is set on the suction side of the wing model. By changing the induced flow direction, i.e., either blowing or suction, the starting position of the wing-tip vortex generation and the position of the vortex core are changed. Especially, in the case of blowing, the plasma actuator has a significant impact on the wing-tip vortex generation: its starting position is shifted downstream.

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Side jets, which are radial ejections, are formed at a near field in the low-density jet, such as a helium gas jet. Mixing of fluids between the jet and the ambient is enhanced at vicinity of the nozzle exit by the side jets. When the side jets are generated in a helium gas jet, the jet has periodically large velocity fluctuation in the potential core. The side jets were produced in uniform density jets by inputting periodic pulsation with a loudspeaker. The side jets in the pulsed air jets were visualized by using planar laser Mie scattering(PLMS), and the condition for generation of side jets was shown by the turbulent intensity, Reynolds number and non-dimensional frequency. Power spectra of velocity fluctuation in the pulsed air jet are similar to those in the helium gas jet if the side jets are generated.

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The condition of the optimal vortex ring formation induced by pulsating jet flow is investigated experimentally by PIV to estimate the vortex core circulation and size. The waveform of a pulsating jet flow is performed by cosine curves. In the pulsating jet flow conditions, the formation condition of the optimal vortex ring is changed widely from the condition proposed by Gharib, so it is difficult to apply Gharib's condition to pulsating vortex ring. The formation time of the optimal vortex ring can be estimated independent of the pulsating conditions if using the condition, proposed in this paper, which the optimal vortex ring is formed when the propagation velocity of vortex core is equal to the convection velocity of shear layer of jet flow.

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Backward-facing step flow, which is one of typical separated-reattachment flows, is controlled with a synthetic jet. The jet is added at the vicinity of the step edge. The flow is measured with laser-Doppler velocimetry, hot-wire anemometry and particle image velocimetry, and results obtained with these methods are compared. Details of flow field structure including the reverse flow region are clarified with time averaged and phase locked averaged technique. Mixture of fluids in the mainstream and the reverse flow region, which is considered as a cause of displacement of reattaching point, is stimulated by random component of the velocity fluctuation rather than periodic component.

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To clear the time-dependent feature of the cavity in a submerged water jet, we study the high-speed behavior of the cavity development process from the freesurface to the surface of the test spacemen, by means of a high-speed video camera and the VOF-simulation method. It is found that after the waterjet impacts on the surface of the test spacemen, the cavity formes as a cylindrical boundary, whose surface consists of a string-like configuration, within a limited time, and the time series of the cavity behavior well correspond to those simulated by VOF method.

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Sandblast techniques that gas-solid jet impinges on surface of the work are known to process a work surface. Many cases gas is air in general and solid particles are metal, plastics and ceramics etc. The solid particles are accelerated by gas flow and impacts on the work and process it's surface. However the solid particles stream out with gas flow without an impact for fine particles because of large viscosity. For fine processing by means of fine solid particles the viscosity resistance becomes serious obstacle to process surface of the work. When ultrasonic is radiated on the solid particles ultrasonic radiation pressure acts on the solid particles and accelerates it. The radiation pressure is determined by a medium, an acoustic intensity and frequency of the ultrasonic.

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The promotion of jet-stream diffusion may enhance the efficiency of mechanical performance in various industrial devices such as fluid machinery and combustion equipments. Both active and passive means were applied for the control of jet streams. Our previous studies disclosed that diamond-shaped cylinder bundles produce a self-excited oscillating jet-stream flow field having multiple uniform flow-rate groups. The present visualization work deals with flip-flop flow oscillation from a diamond-shaped cylinder bundle with wall concavity. It is disclosed in the efflux jet streak-lines that flip-flop flow oscillations occur with the appearance of large dispersion of the left-and right-ward jet streams.

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The flow separation on a flat plate under adverse pressure gradient was investigated by flow visualization. The strength of pressure gradient was adjusted by changing the angle of the ceiling plate. The results showed that the location of the separation bubble moved upstream by the increase in the adverse pressure gradient.

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The present paper describes the results of numerical and experimental studies of the flow pattern and the displacement efficiency of old water in a cylindrical water supply tank. In the present study a three-dimensional turbulent flow calculation was carried out using FLUENT to solve the flow in the tank. The calculated results for flow patterns and the mean residual concentration of old water were compared with the experimental results and showed good quantitative agreement. The displacement efficiency of old water in the tank having an inlet pipe with a diverging nozzle and an outlet pipe with a circular baffle plate is better than those of the other tanks. The decrease in the displacement efficiency of old water in a tank that has inlet and outlet pipes the center of the tank without a diverging nozzle and a baffle plate is related to the large fluctuation and the recirculation of flow in the tank.

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In this research, a mass transfer process of single rising bubbles is investigated by using PIV (Particle Image Velocimetry) and LIF (Laser Induced Fluorescence) measurement, focusing on a coupling mechanism between the mass transfer (from a bubble to liquid phase) and its surrounding liquid motion. First, both mass transfer process and wake of the single rising bubble were visualized via LIF. Next, the relationship between mass transfer and shape oscillations of the bubble interface is discussed. As a result, the shape oscillations are considered to play an important role in the mass transportation between bubbles and their surrounding liquid. Finally, the mass transportation during a collision of a pair of zigzagging bubbles was investigated. From the results, we conclude that the collision of the bubbles enhances the mass transportation of CO_2 to upward direction.

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We discuss the film flow of liquid lithium planned for the target and coolant of BNCT (Boron Neutron Capture Therapy) using accelerators which makes tumors curable with cell-level selections. The internal structure of the boundary layer in the film flowing down on a guide plate is analyzed assuming that the guide plate is flat. The object of our research is the thin film flow in a vacuum because of the ambiance using accelerators, and they serve both as a target of accelerators and as a coolant for the target itself. The latter role requires high-speed film flow for sufficient removals of proton beam heating. In this paper, we show the design condition to maintain the above thin film flow under these severe conditions.

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We discuss the film flow of liquid lithium planned for the target and coolant of BNCT (Boron Neutron Capture Therapy) using accelerators which makes tumors curable with cell-level selections. We treat of the centrifugal instability to be generated in the boundary layer of the film flowing down on a concave guide plate. The object of our research is the thin film flow in a vacuum because of the ambiance using accelerators, and they serve both as a target of accelerators and as a coolant for the target itself. The latter role requires high-speed film flow for sufficient removals of proton beam heating. In this paper, we predict that the above centrifugal instability will give rise to the transition to turbulent flow in the boundary layer of the film flow.

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In elbow pipe flow, flow-induced vibration is caused by separated flow which occurs at downstream of the elbow. To evaluate flow-induced vibration, it is necessary to accurately simulate pressure fluctuation for the large diameter elbow pipe adopted in the Japan Sodium-cooled Fast Reactor (JSFR). However, it is difficult because of the insufficiency of grid resolution near wall in high Reynolds number flow. Detached Eddy Simulation is applied to the elbow pipe flow of high Reynolds number (3.6×10^6) in this report. As a result, 10Hz peak of the power spectral density of pressure fluctuation and mean velocity distributions around separated region are in good agreement with the experiment. However, in the case which differs in inlet velocity distribution, 10Hz peak is not observed and mean velocity distributions are not agreement with the experiment.

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An experimental study of acoustic resonance generated by a submerged water jet has been carried out using various size of the nozzle and various jet velocities. Sound pressure level is measured by a hydrophone in a small water tank. It is found that the jet with water mixed and the jet without air mixed show higher SPL level than the conventional jet with air mixed. Furthermore, SPL level for the jet without air mixed persists in the downstream section. In addition, the optimum nozzle size and the optimum jet velocity are investigated.

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Recently, the secondary conservative finite difference scheme for the flow on moving grid has been proposed. In this study, we have carried out the direct numerical simulation (DNS) of oscillating grid turbulence subjected to system rotation using the scheme. Then, the effect of system rotation on the turbulent flow is considered with the DNS data. The present numerical simulation reproduced corresponding experimental observations for the flows with and without system rotation. The distribution of kinetic energy showed that the rotation inhibits the decay of kinetic energy in the region away from the oscillating grid. In the system without rotation, the turbulence intensity in the vertical direction produced by the oscillating grid becomes dominant in the region away from the grid, and the turbulence is anisotropic. On the other hand, the anisotropy is inhibited in the system with rotation.

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The turbulent characteristics of fractal-generated turbulence are investigated by using a hot wire anemometer. A fractal-grid is placed at the inlet of a wind tunnel and turbulent characteristics downstream of the grid are measured. The results are compared with turbulence characteristics generated by a classical regular grid at the same mesh Reynolds number.

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