Phase lag between vortex shedding from two tandem bluff bodies

This paper presents a work on the phase lag (φ) between vortex sheddings from two tandem cylinders of various shapes and its influence on fluctuating lift on the upstream cylinder. A differential equation of φ, dφ=[4πfs/(2Vc−dVc)] dx, is derived, where fs is the vortex shedding frequency, Vc is the convective velocity of vortices, and x is the downstream distance from the upstream cylinder. Applying the condition φ=2π   at L*=Lc*, as obtained from experimental data, the equation yields φ=2.44π St(L*-Lc*)+2π  , where St is the Strouhal number, L*L* is the normalized cylinder center-to-center spacing and Lc* is the critical spacing defined as the minimum L*L* at which the upstream cylinder could shed vortices in the gap between the cylinders. This relationship agrees well with experimental data previously reported as well as presently measured.