Kazuyuki Kage

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 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.

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.

Numerical Study of Adjusting Shock Waves Produced in Choking Process of Flows.

In this paper, two kinds of choking processes of flows were numerically investigated. One is the choking process of the flow generated by the shock wave passing over the wedge in a shock tube, and the other is the choking process of the uniform flow produced by sudden reduction of cross-sectional area in a duct. The computations were carried out by solving the two-dimensional Euler-type equations by means of the TVD method. The numerical results agree well with experimental results of the choking process in a shock tube, and clarify the developing process of the sonic line and the effects of choking on the shape and the behavior of the adjusting shock wave produced in the choking process. This shows that the reflected shock wave from the wedge in a shock tube and the shock wave generated at the thoat in the uniform flow develop into adjusting shock wave in the choking process.

Investigations of Transonic Ludwieg Tubes : Part3 Effects of Plenum Exhaust System on Starting Process of Tunnel Test Section

The starting time of a transonic Ludwieg tube is dependent on the timing of opening the main tunnel valve and the plenum exhaust valve, as well as the plenum chamber volume, the exhaust rate, the opening times of the main and the exhaust valves, and so on. In the previous paper, the starting process of the transonic Ludwieg tube with a main valve downstream of the transonic test section was studied in the case that the main and the exhaust valves started to open simultaneously. In the present paper, starting to open the plenum exhaust valve was delayed or advanced from the opening of the main valve, and the effect of plenum exhaust delays on the staring time of the transonic test section was discussed. Further, the effect of the orifice position in the plenum exhaust system on the starting time was experimentally investigated. The starting time becomes a little smaller by locating the orifice at the downstream section of the exhaust valve.