Evaluation of pressure field and fluid forces on a circular cylinder with and without rotational oscillation using velocity data from PIV measurement

An experimental method for evaluating pressure field and fluid forces on a bluff body structure is studied using instantaneous velocity data measured by particle image velocimetry (PIV). This method solves a pressure Poisson equation numerically with the experimental velocity data by PIV. The measurement of the velocity field around a circular cylinder is carried out using two CCD cameras placed side by side, which allows simultaneous measurement of velocity near and far field around the circular cylinder. The pressure and fluid forces on the stationary cylinder evaluated by this method agree closely with those in the literature, suggesting the validity of this technique. The present technique is also applied to a circular cylinder with rotational oscillation at Reynolds number 2000. It is found that the drag force on a circular cylinder is magnified at low-frequency oscillation and reduced at high-frequency oscillation. The drag coefficient at high-frequency oscillation is reduced by 30% with respect to the stationary cylinder, while the fluctuating lift is slightly increased due to the generation of synchronized vortex shedding at high-frequency oscillation.