Shock tube study of the drag coefficient of a sphere in a non-stationary flow

Abstract

A review of previous attempts to study the drag coefficient of a sphere in a non-stationary flow, experimentally, is given. Thereafter, a detailed account of the present study is presented. A shock tube facility was used for inducing relatively high acceleration in small spheres laid on the shock tube floor. The spheres acceleration resulted from the drag force imposed by the post shock wave flow. Using double exposure holography, the spheres trajectory could be constructed accurately. Based upon such trajectories, the spheres drag coefficient was evaluated for a relatively wide range of Reynolds number (6000 < Re <101000). It was found that the obtained values for the sphere drag coefficient were significantly larger than those obtained in a similar steady flow case.