The study of Karman vortex shedding for elliptical and rectangular cylinders

Vortex shedding frequencies were measured experimentally with a hot film anemometer behind elliptical and rectangular cylinders at 0, 30, 60, and 90 deg angles of attack between Reynolds number of approximately 2000 and 23000. The ellipses were of eccentricity 0.650, 0.866, and 0.950 with the rectangles cross section width to length ratio of 0.760, 0.500, and 0.312. Vortex shedding frequencies in the near wake of these cylinders were analyzed by means of the non-dimensional Strouhal number. The Strouhal number was presented in terms of a reference length based upon the cylinders projected frontal width and a near wake formation region length and compared to the accepted Strouhal number of 0.21 for circular cylinders in the irregular Reynolds number range. A near wake formation region reference length was extracted from flow visualization measurements in a water tunnel and used to calculate a universal Strouhal number for the elliptical cylinders between Reynolds number 2200 and 7200 and rectangular cylinders between Reynolds number 2200 and 8900. Obtaining a universal Strouhal number for the rectangular cylinders was unsuccessful, but a universal Strouhal number of approximately 0.3 was determined for the elliptical cylinders.