非定常運動翼後流の渦流れと非定常推進力(流体工学,流体機械)  [in Japanese] Vortex Flow and Dynamic Thrust of an Unsteady Airfoil(Fluids Engineering)  [in Japanese]

In order to clarify the vortex flow behind a pitching/heaving airfoil and the characteristics of dynamic thrust acting on them at low Reynolds number region, we have carried out PIV measurement behind both airfoils and have measured the dynamic thrust acting on them. Increasing the nondimensional velocity in pitching/heaving motion, the thrust producing vortex street is clearly formed behind both airfoils. The averaged dynamic thrust acting on them increased as the non-dimensional velocity increased. The hysteresis loops of dynamic thrust acting on a pitching/heaving airfoil had concavity/convexity shape characteristics, respectively. The behaviors of the dynamic thrusts strongly depend on the non-dimensional trailing edge velocity and the non-dimensional heaving velocity. The thrust efficiency of a pitching airfoil increased up to V_p=Q. 7 and the maximum thrust efficiency was 0.34. On the other hand, the thrust efficiency of a heaving airfoil increased up to V_h=0.4 and the maximum thrust efficiency was 0.20.