The focused ultrasound wave attracts attention in the medical field in various applications such as High Intensity Focused Ultrasound (HIFU). An amount of sound energy is generated by focused ultrasound in the body of narrow area. Present HIFU treatment cannot be applied to the part surrounded by bones, such as brain, because focal point is changed by refraction and reflection of ultrasound. In this research three-dimensional transskull ultrasound propagation is analyzed by finite difference method for HIFU treatment to brain. Assumption of isentropy and small disturbance of Euler equation gives the governing equation. The density and speed of sound of each medium are given at the center of Cartesian grid cells so as to model arbitrary human body from Computerized Tomography scan images.

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The unsteady noise related to bubbles in a drain pipe connected to a water tank was investigated experimentally. The noise consisted of two different characteristics noises, that is, the noises due to separation of bubbles from air column and formation of a large cavity on upper surface of the drain pipe. These two types of bubbles were investigated by flow visualization by using a high speed camera and noise was measured by a directional microphone. These results are presented in this paper.

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Temperature distribution visualized by liquid crystal suspension method indicates the heat diffusion process in a rotating drum filled with fluid heated with the rotating center shaft. When the flow is governed by a heat convection generated by a buoyant force acting on the heated fluid, the high temperature fluid raises up and piles up in the upper area of the drum. When the flow is governed by a forced convection by shear force from the wall of the rotating drum, the fluid motion becomes rigid rotation fully or approximately, and the heat radially spreads only by the heat conduction. In the case that the heat convection and the forced convection balance each other and both convection flows are appear, the heated fluid raises up by the buoyant force and is rotated by the rotation inertia force; as the result, the heated fluid is diffused around the drum. These characteristics of the heat diffusion process depend on the Taylor number, the Prandtl number and the heat flux released from the heating shaft.

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To improve efficiency and service life of a fuel cell, it is important to understand dynamic behavior of oxygen molecules in the cell. In other words, we need to know oxygen concentration distribution over electrode planes and inside diffused layers and its time variation. We applied Pressure-Sensitive Paint technique to this problem, attempting to measure distribution of partial pressure of oxygen along micro channels of a fuel cell. To prevent the effect of water produced by power generation process, we developed a water-repellant PSP that can withstand heat and humidity produced by power generation. Using this paint, partial oxygen distributions along the micro channels were successfully visualized, although there were noticeable effects of local temperature distribution on the absolute accuracy for the conditions with higher current densities.

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Yawing moment and side force affect behavior of an automobile in crosswind. In wind tunnel testing, these aerodynamic forces are usually measured using a strain-gage balance. However, using Pressure-Sensitive Paint (PSP), we can measure surface pressure and obtain the force acting on each surface. In the present study, pressure distribution on top and four side surfaces of a simplified car model (1/10 scale Ahmed model) was measured using PSP at yaw angle ψ= 0 and 20[deg]. As a result, we could correlate the negative pressure regions appeared in the PSP images with separated regions and vortices shown in oil flow. In the case of ψ= 20[deg], it was shown that pressure difference between the leeward side and the windward side produced unstable yawing moment.

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Pulsating jets are very common and sometimes useful in industrial fields, due to some differences in basic characteristics from steady jets. In this research, the authors reveal the frequency effect of pulsation on a jet. Experiments are conducted at a Reynolds number of 5,000, Strouhal numbers of 0.13, 0.20 and 0.27 a velocity-amplitude ratio of 0.5. Using an olive-oil smoke, the authors visualize the flow through a nozzle exit and get qualintitative information by PIV technique. As a result, the authors successfully define the locations of main and sub ring vortices. In addition, the authors show the advection manner at 3 frequencies.

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Wind tunnel experiments were conducted to investigate the flow-induced vibrations of a flexibly-mounted rigid cylinder in the free stream exposed to local and periodic turbulence. The turbulence was introduced by a slender rod forced to oscillate in the transverse flow direction upstream of the test cylinder. Results show that the amplitude of the test cylinder increased remarkably as the reduced velocity increased, when the velocity fluctuation with the frequency close to the natural frequency of the test cylinder was introduced to the free stream.

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The drag reduction of a circular cylinder with small grooves was investigated. The positions of upstream and downstream sides of the grooves on the cylinder, θ_f and θ_r, were 50-70°, 55-74° and 60-78° from the stagnation point of the cylinder. Experiments were performed for the above three models and smooth cylinder varying the attack angle α = 0 to 30° in the range of Reynolds number Re = 10^4〜10^5. The Strouhal number of the cylinder with grooves increases from 0.20 to 0.28〜0.30. The surface oil-flow patterns show that the shear layers separated from the front groove of the cylinder reattach on the rear groove of the cylinder. This phenomenon caused by the turbulent transition and turbulent separation. From the previous correlations between drag coefficient and Strouhal number of a circular cylinder with tripping wires, it is expected that the drag coefficient of the circular cylinders with small grooves decreases to about half of that of a smooth cylinder at α + θ_f<80°, in the range of Re >4×10^4.

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The flow around and unsteady fluid dynamic forces acting on a rotating flat plate in an uniform flow were calculated by discrete vortex method. Free flight experiment of flat plate was carried out to determine the falling velocity and rotation number which were used as uniform flow velocity and rotation number in the calculation. The validity of the calculation were comfirmed by comparison with the potential flow theory and visualiation using wind tunnel. Comparison between the result in the case that point vortices were shed and one in the case that no point vortices were shed showed that the effect of vortex shedding on fluid dynamic force become maximum at θ = -90° for drag and at θ = -45° for lift.

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Taylor vortices generated between eccentric and/or concentric rotating cylinders were investigated by experiments and also by three-dimensional incompressible Navier-Stokes simulation. The focus of the research is applied on the control of Taylor vortex cells by the jet injection from the outer cylinder wall. In the present case, 6 stable Taylor vortex cells can be controlled and the number of cells decreased to 4, so that the driving torque applied on the inner cylinder can be reduced dramatically. Furthermore, unsteady behavior of the vortex cells was discussed. These experimental results as well as obtained unsteady flow fields agreed well with those of the numerical results, so that control and reduction of Taylor vortex cells expected by numerical analyses were confirmed in the experiment

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The detailed vortex flow structure behind a combination airfoil at a low Reynolds number region was measured by PIV. Moreover, the dynamic thrust acting on a combination airfoil was measured by a six-axes sensor in water tunnel. The combination airfoil can form clear thrust producing vortex street behind airfoil even at low non-dimensional trailing edge velocity and non-dimensional heaving velocity. Especially, it is possible to form the thrust producing vortex street with high vorticity at ψ= π/2 and π. The jet velocity behind combination airfoil at ψ = π/2 and π becomes over 2.0. The averaged dynamic thrust acting on a combination airfoil increases as the non-dimensional trailing edge velocity and non-dimensional heaving velocity increases, same as case in pitching and heaving airfoils. Moreover, the averaged dynamic thrust acting on combination airfoil at ψ = π/2 and π is much larger than that on pitching and heaving airfoils. However, the maximum thrust efficiency of a combination airfoil at ψ = π/2 was approximately 0.42 and was slightly higher than that on a pitching airfoil.

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Numerical simulation of nonequilibrium shock-layer flows was performed for the reentry conditions of MUSES-C with carbonaceous ablation effects by an extended merged shock-layer theory based on a 4-temperature and 16 chemical species model. The numerical calculations assumed a continuum approach and the system of governing equations constituted a two-point boundary value problem on a stagnation-point streamline, which was solved numerically by the SAR method. The effects of ablation on temperatures and flowfields were discussed in detail. It was found that the ablation from a body surface had significantly influence on various physico-chemical values in the merged shock-layer.

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Radiation of micro-air plasma-jets was measured at low pressure with high spatial resolution, and temperatures were estimated. Radiation measurement was made spectroscopically in the wavelength region of 200 to 900 nm. In the region of 280 to 480 nm, the bands of N_2^+ and N_2 molecules were predominant. Some atomic lines of N and O were observed in the infrared region of 700 to 900 nm. Temperatures of the plasma-jet were estimated with a spectral matching method for N_2^+ 1- bands and Boltzmann plot method for the atomic lines. Rotational temperatures were estimated 5,000 to 8,000 K, and vibrational temperatures 34,000 to 70,000 K, both with some axial variations. Electronic excitation temperatures of oxygen atomic lines were estimated 5,000 to 9,300 K. It was found that the rotational temperatures had large difference from the gas temperature based on an empirical formula for a supersonic free-jet, but decreased downstream in the expansion flow region, and also the vibrational temperatures were much higher than those expected.

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In this paper, the airplane performs a 2-dimensional loop flight. The motion calculation and the fluid calculation are coupled for the investigation of the airplane motion due to the surrounding fluid. In the case of (non-coupled) motion calculation, existing data from experimental values and the steady fluid calculation around wing are used for the coefficients of the aerodynamics force. In the coupled calculation, the fluid calculation is performed for every step of the motion calculation. In the fluid calculation, the grid of wing model rotates corresponding to the pitching angle θ for every step of the fluid calculation. For loop flight, the pitching moment coefficient C_M is corrected by correction value decided by the pitch angle θ. Trajectories of the airplane by the motion calculation and the coupled calculation are compared.

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IFEM (Immersed Finite Element Method) is an extended method from Immersed Boundary Method which is familiar as Finite Difference Method. In IFEM, the motion of structure is described as Lagrangian while that of fluid as Eulerian, and then the fluidstructure interaction force is added to the equations of motion for fluid using Dirac delta function. Therefore the reproduction of fluid meshes is not necessary. In the present paper, the conventional IFEM that is frequently utilized for fluid and flexible elastic structure interaction problems is applied to fluid-rigid bodies system by introducing the simple evaluation of internal force as zero and the reassignment of average velocity to rigid body.

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Recent years, developments of a computer have enabled to analyze a complicated problem in the area of fluid dynamics. Flows with moving boundaries can be encountered in many practical situations; among those in which considerable research interest are in-cylinder flows in positive displacement pump, flows in blood vessels, etc. However many numerical methods of unsteady flow have been presented, numerical analyses with moving boundary have been considered by few papers. In this study, arbitrary-Lagrangian-Eulerian method is employed to analyze the in-cylinder flow that has moving piston. To validate computational accuracy, we carried out measurement of the flow by Particle Image Velocimetry method. Computational results are in good agreement with experiments, but there were some difference of vortex structure.

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The purpose of this work is to know the fluid flow of an oil damper by numerical simulation, so as to obtain the exact values of the damping coefficient of the oil damper. The Finite Difference Method (FDM) was used for solving the flow formation caused by the moving piston. Each time step proceeded in the Fractional Step method, and the Arbitrary Lagarangian-Eulerian (ALE) method was used for the moving boundary. In order to stabilize the computation in the moving boundary problem, we employed the masking method with single block grid system. That is, the algebraic grid generation using stretching function was used for moving piston. The time dependent coordinate system in physical domain which coincides with a contour of moving boundary is transformed into a fixed rectangular coordinate system in computational domain. The computational result was compared with the experimental one and the approximate solution. The results of present analysis show good agreement with the experimental results of wide range of piston diameter.

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In these years, a variety of numerical simulations are performed under the favor of computational performance and the progress of computational methods. Especially in FSI(Fluid-Structure Interaction) Analysis, flow is analysed in consideration of object's transformation by flow force. The objective of this research is FSI inverse analysis. In FSI inverse analysis, stress distribution is calculated from displacement of the object, and flow is calculated from the stress distribution. Here, the two dimensional FSI analysis was done for flow around the elastic square cylinder. The change of flow by the object's transformation in consideration of flow force was ascertained. The two dimensional FSI inverse analysis was done for flow around the elastic square cylinder. The computational result of FSI inverse analysis is verified by FSI analysis.

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Three-dimensional large-scale numerical simulations were carried out to predict the complicated two-phase flow characteristics in a fuel bundle of an advanced light water reactor. Conventional analysis methods with a two-fluid model need composition equations and empirical correlations based on the experimental data. Therefore, it is difficult to obtain high prediction accuracy when experimental data are nothing. Then, a new two-phase flow analysis method was proposed and the TPFIT code was developed. This paper describes the predicted two-phase flow behavior in the simulated fuel channels with the TPFIT code, and the predicted liquid film behavior around a curved fuel rod with the FLUENT code which is one of the most famous commercial codes. In addition, flow visualization experiments were carried out to understand the liquid film behavior on the curved fuel rod. These results reflect the thermal design of the advanced light water reactor core.

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The distortion process of the compression wave in a ballast-tracked tunnel was investigated by field measurement and numerical simulation. The field measurement was conducted in an actual Shinkansen ballast-tracked tunnel of about 4 km. The numerical simulation corresponding to the field measurement was carried out on the basis of a one-dimensional compressible flow analysis in which the effects of steady and unsteady friction were included and of an acoustic analysis on the effect of side branches. The results of the numerical simulation agreed well with those of the field measurement. It indicates that the ballast is effective for reducing pressure gradient of the compression wave generated by a high-speed exceeding 350km/h.

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Unsteady RANS simulations were performed to clarify unsteady aerodynamic interaction in a turbine stage performance. Blade-count ratio is almost the same as that of the real turbine concerned. The flow fields are measured for three axial spacings between rotor and stator using five-hole pitot probe downstream of the blade row, and we have compared experimental time-averaged pneumatic pressure data with the corresponding numerical results. Detailed comparisons are then made to elucidate the effect of the axial spacing especially on the stage performance from a time-averaged and unsteady point of view.

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Cooling fan in PCs or small vacuum pumps is generally used in narrow space. In such cases the fan performance and flow field are quite different compared to these in design usage. In this study, we measure the flow field and performance of the fan used under realistic conditions. We use slant-type hot-wire probe for a measurement and performed a detailed measurement about a three dimensional unsteady flow field. Furthermore, we compare calculated results with the experiment result.

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This paper deals with experimental and numerical studies of a low-pressure turbine blade whose solidity is changeable. The purpose of this study is to clarify the effects of imcoming wakes upon the aerodynamic loss of the cascade, in particular, under low Reynols number conditions and reduced solidity condition. Cylindrical bars move in front of cascade to introduce wakes. Pneumatic probe mesurement is made to obtain total pressure loss distributions downstream of the cascade. Surface pressure distributions around cascade are measured to investigate flow field around the surface. Besides, LES simulation is also executed to investigate the ef fects of imcoming wakes for the aerodynamic loss and the boundary layer.

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This paper deals with experimental and numerical simulation of boundary layer on a low pressure turbine blade. The purpose of our study is to maintain or increase the effeciency even for reduced solidity by taking advantage of wake from upstream cascade to suppress separation bubble on the sucssion surface. Therefore it is very important to clarify sepalation-bubble transition with and without wake-passing. Boundary layer mesurement is first conducted used of hot-wire-anemometer followed by large-eddy-simulation, in paticular, focused on unsteady phenomena in the sepalation-bubble transition process.

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Effects of air separators on the improvement of stalling characteristics of axial flow compressors were investigated on a lowspeed single-stage fan. The best arrangement of the air separator has proved to be able to eliminate completely the stall zone of the original solid-wall characteristics with almost no loss in the stage efficiency. The effective relative axial location of the device against the rotor blade tip suggested that the improvement has been achieved by the separator continuously removing deteriorated flow around the blade tips.

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