周期流の圧力勾配が振動翼の剥離と揚力に与える影響

抄録

We investigate the effects of pressure gradient by a periodic flow on the separation and lift of an oscillating wing. The periodic flow is a freestream velocity changing sinusoidally in the mainstream direction. We conduct an experiment on the oscillating wing using a water tunnel at Reynolds number 3800. Velocity fields are obtained by particle image velocimetry (PIV), and lift coefficient acting on the wing is directly measured using a load cell. The lift coefficient is greater in freestream acceleration than its deceleration. The velocity data from PIV shows that the separated flow becomes attached due to the negative pressure gradient in the range of freestream acceleration, and the evolution of separated flow occurs near the trailing edge due to the positive pressure gradient in the range of freestream deceleration. A numerical simulation is carried out to investigate the velocity fields on the wing surface in more detail. It is found that the flow separation occurs near the leading edge as well as the trailing edge during freestream deceleration. These separated flows probably affect the lift coefficient of the oscillating wing.