where Sr is the Strouhal number, f is the frequency of vortex shedding, D is the hydraulic diameter of the object in the fluid flow and V is the velocity of the fluid. The Strouhal number is a function of the Reynolds number Re and in the region 200<Re<200,000 it is assumed to be equal to 0.2.
See also: dimensionless number (which includes a listing of other dimensionless numbers)
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