The Effects of Turbulence and Unsteadiness on Vortex Shedding from Sharp-Edged Bluff Bodies

Motivated by a desire to evaluate vortex shedding flow meters for measuring velocity in unsteady turbulent flow applications, the objective of our work was to study the effects of flow disturbances on vortex shedding from sharp-edged bluff bodies. In particular, the combined effects of turbulence and unsteadiness were examined, as well as their separate effects using controlled wind tunnel tests. After I Introduction The phenomenon of vortex shedding from bluff bodies has been studied since the pioneering work of Strouhal (1878) and Von where / is the vortex shedding frequency, D is the bluff body diameter, and U is the mean free-stream velocity. Over a wide range of Reynolds numbers, the Strouhal number is constant, implying a linear relationship between shedding frequency and mean velocity. The idea of building a flow meter based on the assumption of a constant Strouhal number was first proposed by Vortex shedding flow meters have been used in steady flows for over two decades and have proven themselves to be reliable and accurate. The benefits of this type of flow meter include high accuracy, linearity, wide dynamic range, and high reliability (no moving parts). However, in many potential applications, disturbances in the form of free stream turbulence and periodic unsteadiness may degrade meter performance by changing the Strouhal number, decreasing signal-to-noise ratio, or forcing the shed vortices to "lock-on" to the periodic disturbance frequency. Hot-wire measurements by Motivated by the desire to use vortex shedding flow meters to monitor velocity in unsteady turbulent flow applications, the objective of our work was to study the individual and combined effects of these disturbances on vortex shedding from sharp- 1