Impulsively-started flow about rectangular cylinders

Impulsively-started flow about sharp-edged rectangular cylinders has been investigated experimentally. The forces acting on the bodies have been determined, as a function of the relative displacement of the fluid at a subcritical Reynolds number, for various angles of attack. The results have shown that the shedding of the first two or three vortices and the manner in which they are generated have profound effects on all the characteristics of resistance. The results have also shown that the drag force in the transient state is always larger than that in the asymptotic steady state, pointing out the importance of the understanding of impulsively-started flow about bluff bodies. The data presented here are expected to form the basis of future numerical analyses of similar time-dependent flows. At present, accurate analytical and numerical data, for comparison with those presented herein, do not exist, save for the later stages of motion where the behavior of flow becomes nearly identical to that of steady flow. http://archive.org/details/impulsivelystart1094519845 Lieutenant Commander, United States Navy Approved for public release; distribution is unlimited.