Yukio Ishibashi

Analysis of Submerged Water Jets by Visualization Method: Flow Pattern and Self-Induced Vibration of Jet

This paper is concerned with an experimental investigation on plane submerged water jets discharged into quiescent water in an open channel. Flows are visualized by using hydrogen bubbles, solid particles and dye. The results show that the jets attaching to the water surface by the Coanda effect are classified into six types according to their behavior after issuing from the nozzle, and that the self-induced vibration of the jet, which is one of six flow patterns, occurs under the condition of the reduced Froude numberFr*≒0.7∼1.0. An additional analysis of the photographs reveals that the self-induced vibration of the jet is caused by attachment of the jet to the water surface and the ensuing bifurcation of the jet at an attachment point, and that the frequency of vibration is independent of the water level.

Ferromagnetic fluid flows in a rectangular channel with travelling magnetic fields

Abstract Experiments were made on the laminar flow of a water-based ferromagnetic fluid with alternating, travelling magnetic field from 3 to 50 Hz. The pressure difference was found to be induced in the opposite direction to the field, but it was so small to be appreciable at high Reynolds numbers.

Experimental studies of viscoelastic fluid flow

Abstract The extruded flow of polymer solutions from a reservoir through a capillary with a sharp-edged entrance is studied experimentally, and the following results are obtained. (1) It has been reported that the viscoelastic fluid flow through a capillary is unstable above a critical shear rate. However, when a shear rate exceeds the critical shear rate by a factor of ten, or so, the extruded polymer solution does not show the “Barus effect” at the exit of the capillary. The extruded polymer solution begins to swell at some distance from the exit of the capillary and this distance changes periodically. (2) the jet ejected from a capillary swings periodically in an electrostatic field.

Interfacial waves of the magnetic fluid in vertical alternating magnetic fields

Abstract The stability of the surface of a magnetic fluid layer under the influences of vertical alternating magnetic fields was investigated experimentally and analytically. Two kinds of waves were excited on the surface and the critical conditions for the onset and the wavelength of these waves were obtained.

Resonance of Circular Shock Wave

In supersonic centrifugal compressors or disc MHD power generators, oscillation modes of the circular shock wave can be caused by the static change or the dynamic change of the back pressure. While previous studies, which included only the former effects, were carried out both experimentally and theoretically, the latter effects of forced oscillation are considered here. The excitation of the back pressure fluctuation in a downstream stagnation chamber was accomplished by rotating a butterfly valve. The pressure fluctuation was measured to investigate the resonance of the circular shock wave at concentric positions in the vicinity of the first shock and in the downstream stagnation chamber. A-D-converted signals were statistically correlated to extract the spacial oscillation modes. Resonance was confirmed to occur when the excitation frequency was near the natural frequency of mode 0. Furthermore, the small pertubation of the higher harmonic modes in the downstream stagnation chamber influenced the oscillation modes of the circular shock wave.

Instability of Magnetic Fluid Surface under Horizontal Non-Uniform Alternating Magnetic Field.

Stability of the surface of a magnetic fluid under a horizontal non-uniform alternating magnetic field is investigated experimentally and analytically. Several modes of interfacial waves of the same frequency as that of the applied magnetic field are observed, and the critical strength of the magnetic field at each frequency were obtained. The linear stability theory shows that the system is destabilized with the increase in the magnetic susceptibility and the gradient of the magnetic field, which is in accord with the experimental result. The iron nitride magnetic fluid, which is newly developed and has very high susceptibility and magnetization, was tested under the same condition as W-35 and HC-50. The small disturbance occurred even at very weak magnetic field, and the steady wave was formed in the uniform magnetic field.