Particle capture by a circular cylinder in the vortex-shedding regime

Particle capture, whereby suspended particles contact and adhere to a solid surface (a 'collector'), is an important mechanism for a range of environmental processes including suspension feeding by corals and 'filtering' by aquatic vegetation. In this paper, we use two-and three-dimensional direct numerical simulations to quantify the capture efficiency (eta) of low-inertia particles by a circular cylindrical collector at intermediate Reynolds numbers in the vortex-shedding regime (i.e. for 47 < Re <= 1000, where Re is the collector Reynolds number). We demonstrate that vortex shedding induces oscillations near the leading face of the collector which greatly affect the quantity and distribution of captured particles. Unlike in steady, low-Re flow, particles directly upstream of the collector are not the most likely to be captured. Our results demonstrate the dependence of the time-averaged capture efficiency on Re and particle size, improving the predictive capability for the capture of particles by aquatic collectors. The transition to theoretical high-Reynolds-number behaviour (i.e. eta similar to Re-1/2) is complex due to comparatively rapid changes in wake conditions in this Reynolds number range.