Fluid force acting on a rigid sphere in the streamwise oscillating uniform flow

Drag and lift forces acting on a rigid sphere in a uniform streamwise oscillating flow were numerically investigated by means of a three-dimensional direct numerical simulation (DNS) based on a marker and cell (MAC) method. To clarify the effects of the oscillation of the ambient flow and particle Reynolds number on drag force acting on a rigid sphere, numerical results of drag force were compared with the conventional formula of drag force in an oscillating flow. The results show that the time-averaged drag force acting on a rigid sphere in a uniform oscillating flow increases due to the strong fluctuation. The behavior of the drag force on a rigid sphere is in good agreement with the conventional formula of fluid force taking into account the standard drag, the added mass force, force caused by pressure gradient and history force in the particle Reynolds number region of 1 ≤ Re_p ≤100. For Re _p≥300, .A=0.5 and St=0.2, the periodic axisymmetric wakes behind a sphere are found, and the conventional formula of fluid force has the difference from DNS result.