Transition and Strouhal Number for the Incompressible Wake of Various Bodies

Incompressible wakes behind three-dimensional bluff bodies have been studied in order to gain information about the effects of body geometry. The results of Magarvey and Bishop achieved by dropping liquid droplets through another liquid were duplicated using solid spheres, and observations were made of the wakes of bodies of various shapes, particularly cones. It was found that wake transition, defined as the first occurrence of finite unsteadiness, could be approximately correlated for a range of spheres and cones by a Reynolds number based on the total wake momentum thickness, θ2 = CDA/2π, Reθt ≈ 95. The cases of the teardrop and the disc deviate from this correlation, and explanations are discussed. It was also found that for regular vortex shedding the data for spheres and cones could be correlated with the Rayleigh-Strouhal formula based on θ; Sθ=0.305 [1−(95/Reθ)].Constraining the body to travel along a wire, thus reducing body-fluid interactions, produced an aperiodicity in the shedding phenomenon but left the value of the Strouhal number effectively unchanged.