The motion of kelp blades and the surface renewal model

Abstract

We consider how the flapping of kelp blades may enhance the flux of nutrients to a blade, by stripping away the diffusive sub-layer and renewing the fluid at the blade surface. The surface renewal model explains the degree of flux enhancement observed in previous studies under different flow and flapping conditions. We measured the motion of real kelp blades of Laminaria saccharina, Macrocystis pyrifera, and Nereocystis luetkeana under uni-directional current in a laboratory flume. Observed flapping frequencies coupled with the renewal model, suggest that the flapping of blades in the field has the potential to significantly enhance flux to the blade surface at low current speed, but has little effect on flux at high current speeds.