Toyoyasu Okubayashi

Numerical Study of the Effects of the Rupture Process of a Secondary Diaphragm in Expansion Tubes

AbsractThe results of a numerical study are described in which the interactions of a primary shock wave with a secondary diaphragm in expansion tubes are taken into account. The developing wave pattern in the interacting process of the shock with a secondary diaphragm are visualized by many kinds of figures (e.g., the time-distance diagrams of the wave phenomena on the axis, the acoustic impedance contours, and the time histories of the pitot pressure on the axis), and the influences of the shape and rupture process of the diaphragm on the quality of the test gas are explored.

Numerical Study of Entry Waves Produced by High-Speed Trains Entering a Tunnel. Effects of Nose Shape of Train.

In this study, entry waves produced by high-speed trains which enter a tunnel were numerically investigated. The equations of the one-dimensional, unsteady and compressible flow with mass removal in which the area of a tunnel is dependent on the time and distance were numerically solved by the method of characteristics. The calculations were performed for trains with various nose shapes in the case in which the speed of the train was 300km/h, and the effects of the nose shape of the train on the entry waves were quantitatively clarified. As a result, the optimum condition of the nose shape which forms the entry wave with minimum pressure gradient was shown.

Visualization of Flow Around a Savonius Rotor Blades

The Savonius rotor with two semicylindrical blades is known as a dragtype wind turbine of vertical axis operation. The visualization of the flow fields around the Savonius rotor blades were observed by the tracer method using aluminum powder suspended in the water stream. The flow visualization was carried out for the absolute and relative flows with rigid and rotation camera devices.In the case of stationary rotor, the effect of flow through the overlapping section decreases of a minus torque acting on the returning blade. The torque and power performances of rotating rotor were considerably improved by Coanda-like flow on the convex side of the advancing blade.