The Effect of Collector Motion on Particle Capture Efficiency

Particle capture is central to many fundamental processes in aquatic systems including suspension feeding and submarine pollination. Our current model of understanding and predicting particle capture efficiencies (η) is through the application of rigid cylindrical collectors over a limited range of collector Reynolds number (Re_c), which does capture the full range of environmentally relevant flows or collector behaviors. Recent computational modelling efforts have advanced this model by examining the effect of collector motion on particle capture. Specifically, the models have predicted a difference in particle capture efficiencies between longitudinal motions of collectors caused by unsteady flow and transverse motions of collectors due to vortex shedding. This study examined the effects of collector motion in the transverse and longitudinal direction on capture efficiency using a cylindrical model in the lab and a wind-pollination grass (Phleum pratense) in the field. Results from the both experiments indicated that movement increased particle/pollen capture efficiency and distribution, especially at low Re_c. This effect was greatest for transversely moving collectors with large magnitudes of motion, which encountered more particles with higher relative momentum. Results provided helpful insight into controversies in the literature. Importantly, it showed that collector motion can lead to different particle capture efficiencies than those predicted by the standard (rigid) model indicating that collector motion should be considered when examining the aforementioned processes.