Katsuya Ishimatsu

A Comparative Study of Navier-Stokes Calculations and Experiments for the Savonius Rotor

This note compares the numerical calculations from the two-dimensional Navier-Stokes equations with experimental streakline and pressure distribution data for an operating rotor at maximum power conditions

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 Shock Waves Propagating in Bmanched Ducts. The Generating and Diminishing Process of the Nonuniformity of the Shock Front.

In this paper, the generating process and the diminishing process of the nonuniformity regarding the strength and the shape of the shock wave front propagating through branched ducts were explored by numerical simulation. Computations were carried out by solving the two-dimensional compressible Navier-Stokes equations by using the total variation diminishing (TVD) scheme. Computations were performed for six types of branch (90° branch, 1/2 size 90° branch, T-shape (1/1, 1/2, 1/3 size) branch, 45° branch) and two incident shock Mach numbers (Ms=1.3, 2.0). The flow field were numerically visualized by the pressure and vorticity contours, velocity vectors, pressure distributions on the walls and time histories of the pressure contours on the walls. The mechanism of the generating process and the diminishing process of the nonuniformity of propagating shock front was clarified.

Numerical Study of Shock Waves Propagating in an Elbow. Effects of Elbow Angle.

In this paper, the shock wave propagating in an elbow and the transient flow induced by the shock were investigated numerically in order to clarify how the shock wave transmitted past the elbow is stabilized to uniformity by the effects of the elbow angle. Computations were carried out by solving the two-dimensional compressible Navier-Stokes equations using the total variation diminishing (TVD) scheme. Calculations were performed for six elbow angles between 5° to 120°, and the flow fields were numerically visualized by the contour lines of pressure, sonic lines, pressure distributions and wave diagrams. The numerical results showed that the distance for which the nonuniformity of the transmitted shock continued became longer with increasing elbow angle and the attenuation of the transmitted shock was very small.

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.