The dynamic behavior of a sports ball has a close relationship with fluid dynamics. The seams and/or dimples on the ball surface affect the lift and side forces as well as the drag as it flies through air. This often causes erratic flight paths. In the case of baseball, a slowly rotating ball also manifests this behavior. It is believed that this is caused by the flow separation that occurs asymmetrically over the baseball. In the present experiment, the characteristic of the force acting on a baseball is measured with a load cell and the flow field at and behind the seams of the baseball is visualized with a smoke-wire technique. Three-dimensional wake patterns associated with various ball and seam orientations were identified.

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In order to reduce the noise level in super sonic wind tunnel, a laminarization of the boundary layer in wind tunnel constraction is essential. Detailed measurements were conducted in the wind tunnel equipped at National Aerospace Laboratory (NAL) and Institute of fluid Science Tohoku Univ (IFS). Spanwise wavenumber of the disturbance of some streamwise potitions are computed by using the maximum entropy method (MEM). Results show that downstream spanwise wavenumber generated via Gortler vortices is smaller than upstream one.

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This paper describes a prediction of the laminar-turbulent transition on a swept wing using linear PSE (Parabolized Stability Equations). The linear PSE includes the effects of nonparallel mean flow, body curvature and streamline curvature which have been ignored in the classical analysis based on Orr-Sommerfeld equation. The result shows that the wall curvature has significant effect on the growth rate of the unstable disturbances. The comparison with experimental shows fairly good agreement in the wavelength of the most unstable mode.

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Cavitating water jets have been successfully applied in fields of engineering, such as cutting, cleaning, peenings and so on. The erosion ability of the jets is considerably affected by the nozzle geometry. Thus, clarification of the behavior of cavities formed by submerged water jets is considered to be one of the most useful methods for clarifying the mechanism of erosion for the nozzle geometry. We systematically analyzed the cavity area and the cavity width with respect to time and standoff distance for two nozzle geometry, i. e. a cylindrical nozzle and a conical nozzle. The cavity changes successively markedly in length, in area, in width in the periodic process of the cavity, such as the growth, the shedding and the collapse. The fluctuating amplitude of the cavity length for the cylindrical nozzle is higher than that for the conical nozzle. In short, the erosion ability depends greatly on the unsteady behavior resulting from the nozzle geometry, and for the cylindrical nozzle, the ability is comparatively high.

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This paper deals with thermal characteristics of aluminium as phase change material. Aluminium releases latent heat of 320 kJ/kg at melting point 660℃. It is clarified by experiment that heat release amount of aluminium is large about 20〜40% than prior magnesia heat storage material of sensible heat type.

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This paper presents an experimental study of the fluid dynamics during the impingement of a liquid droplet upon a rough solid surface. Sample liquids used in the experiments were dyed water with black ink and kerosene-based ferricolloid HC-50. The impact process was observed using a three dimensional motion analysis system. The target was a piece of sand paper that was bonded to the hard rubber mat. Particular attention has been paid to the comparison of the water drop impacts with the magnetic fluid drop impacts. Effects of the surface roughness and magnetic fields on the impact phenomena were revealed.

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Heart treatments with an ultrasonic vibration has been carried out for microstructural control in solid state materials. Post 60% cold-rolled aluminum specimens were subjected to the ultrasonic heat treatment at 573K, and changes of microstructures were analyzed by a FE-SEM/EBSP/OIM. The condition of the ultrasonic vibration used here was 48.5kHz in frequency, 1.5μm in displacement amplitude and 5.8MPa in stress amplitude. We found that the application of an ultrasonic vibration could enhance the recrystallization. Of particular interest is that the higher was vibration stress amplitude, the more occurred recrystallization. The OIM observation revealed that as the stress amplitude was increased, the recrystallized grains tended to be refined and to have a texture. The frequency of low energy boundaries increased as well. From the analogy of microstructural change by fatigue, the ultrasonic vibration stress would encourage the formation of dislocation cell structures. The rearrangement of dislocation structure by the ultrasonic vibration should contribute to enhancement of recrystallization.

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Experimental studies of the aerodynamic characteristics of insect wing gliders have been performed. In the first place, the curved surfaces of insect wings were measured with a three-dimensional curved shape measuring system. The experimental apparatus consisted of the light microscope system, laser displacement detector system, automatic scanning XY stage system and automatic focusing system. The surface roughness of insect wings can be measured with μ m order accuracy. In the next place, gliders were made using insect wings. Gliding performance of insect wing gliders was examined with a high speed video camera. The morphological and gliding characteristics were revealed for some insect wings.

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