Abstract
It is interesting to study flow field around a moving body and flow force acting on it. Studies on vortex flow and vortex structure have been conducted actively. Here are introductions on two kinds of vortex flows around moving boundaries, one of which is experimental results on motion of vorticies around an elastic airfoil surface and the its wake flow as an example of external flow. Another of which is an example of internal flow that is an effective usage of vorticity as a parameter to characterize flow condition. Simulation results on internal flow in a piston head chamber of an oil-hydraulic cylinder show that there are characteristic two kinds of flow patterns, three-dimensional vortex flow pattern and one-dimensional parallel flow pattern.
