| Budget Amount *help |
¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1995: ¥300,000 (Direct Cost: ¥300,000)
Fiscal Year 1994: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
Unsteady behavior of a tip leakage vortex affected by periodic gust, and the one generated from an oscillating blade, were experimentally studied with a three-sensor hot-wire anemometer.The experiment was conducted in a low-speed wind tunnel in which a blade was set with a clearance between its tip and the tunnel wall.The periodic gust from rotating cylinders was introduced to the blade, and the three dimensional flow velocities were measured at downstream positions.When the wake reached the blade leading edge, the tip vortex was observed to diminish, and then it gradually regained the vorticity.The vortex center was found to oscillate with a large amplitude in the direction of blade thickness.It was thus clarified that the tip vortex was quite strongly affected by the incoming gust.The tip vortex generated from an oscillating blade was then detected by the hot-wire anemometry.The in-phase oscillation of the tip vortex with the blade oscillation was clearly observed.The change in the phase of the vortex oscillation in the downstream direction could be explained by the convection of the vortex due to mean flow.In the final stage, the unsteady pressure distributions were measured on a flat plate set at a downstream position of the oscillating blade, The surface pressure substantially decreased due to the passage of the oscillating tip vortex, and, thereby, the unsteady aerodynamic force on the flat plate was significantly changed.When the tip vortex moved across the flat plate, its position changed widely in the spanwise direction.The unsteady pressure field was accordingly changed in a wide area in the spanwise direction.A theoretical study was performed at the same time, in which a new singularity method was developed to estimate the induced unsteady aerodynamic force by the unsteady tip vortex with arbitrary vorticity and position.
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