A circular cylinder is tested in crossflow over the subsonic speed range. Time-resolved pressure distributions give\udinformation on surface pressure fluctuations; the corresponding drag and base drag coefficients are provided.\udMeasured base pressure fluctuations at low Mach numbers are in agreement with the findings of other researchers.\udFlowchanges at higher subsonic velocitiesandinto the transonic range are described. Illustrations aredrawnfrom the\udobservations of other researchers, enabling physical explanations to be given to assist toward amoregeneral modeling\udof theproblem.AtMachnumbersabove0.6 thechangingstrength of the vortices reduces thebase dragcoefficientupto\udaMachnumber of 0.9, at which the onset of sonicflowincreases the drag. Strouhal numbervariation is compared with\udthe measurements of other authors. The paper concentrates on providing reliable measurements of vortex shedding\udand base pressure over the subsonic speed range rather than attempting to provide universal correlations.
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