Base Pressure Measurements on a Circular Cylinder in Subsonic Cross Flow.

A circular cylinder was tested in cross flow over the subsonic speed range. Timeresolved pressure distributions give information on surface pressure fluctuations and the corresponding drag and base drag coefficients are provided. The Strouhal number variation is compared with the measurements of other authors. Flow changes at higher subsonic velocities and into the transonic range are described. At Mach numbers above 0.6 the changing strength of the vortices reduces the base drag coefficient up to a Mach number of 0.9, where the onset of sonic flow increases the drag. Time-resolved base pressure fluctuations at low Mach numbers are in agreement with the findings of other researchers with regard to the relative time spent in vortex formation and shedding. As the Mach number increases the time spent in vortex formation becomes equal to that spent in shedding. The paper concentrates on providing detailed base pressure data rather than attempting to produce universal correlations. Physical explanations have been given, where possible, to assist toward a more general modeling of the problem.