234 はく離直前の流れ場変動(G05-3 剥離制御・抵抗低減,G05 流体工学)  [in Japanese] 234 Flow Fluctuations before the Onset of Separation  [in Japanese]

Jets issuing through small holes in a wall into a freestream have proven effective in the control of flow separation. This technique is known as the vortex generator jet method (VGJ). If a precursor signal of separation is found, the separation control system using VGJ can be operated just before the onset of separation. Therefore, flow field with no separation is always attained. In this study, to generate managed separation, the divergence angle of the diffuser was controlled by a stepping motor. Flow separation occurs when the divergence angle reaches at 20 degrees in our experimental condition. The distributions of the velocity and turbulence intensity of the air flow were measured by using an X-type hot wire probe. The vertical turbulent intensity at the upstream location of the divergent portion is enhanced before the onset of separation.