Vortex Shedding from Rectangular Plates

摘要

Experimental studies of vortex shedding from a rectangular elongated plate, when the cord length parallel to the flow (c) is much greater than its height (t), show that the Strouhal number Sr(c) increases stepwise with c/t increasing from 3 to 12. Investigating a flow phenomenon described by a frequency f, one can consider a Strouhal number Sr = f l/u as a nondimensional frequency when l and u are characteristic length and velocity, respectively. For a phenomenon considered in this Note, l = c/m and u ≈ 0.5-0.6U are a natural choice for characteristic parameters, when m and U are the number of vortices (bubbles) formed on the plate's side and the freestream velocity, respectively. This was confirmed numerically for Reynolds numbers Re = Ut / v > 300. Assuming that vortex shedding has a traveling-wave nature, we suggest simple considerations for explaining the trend of the Strouhal number to increase stepwise.