Estimation of the turbulent kinetic energy in vegetated channels from the perspective of vortex dynamics

Abstract

Turbulence has been recognized as the main driver of sediment incipient motion in vegetated regions, where the turbulent kinetic energy (TKE) linked to stem wakes exceeds that associated with bed shear and the classical bed shear-based model is no longer valid. Presently, the vegetation-generated turbulence within the emergent canopy of rigid cylinders is described from the perspective of vortex dynamics (i.e., how plant-induced eddies drain kinetic energy from the mean flow and feed it directly into turbulence), instead of the TKE budget balance generally in use. A few theoretical hypotheses on stem wake flow (including the volume, turbulence density, and turbulent energy of Karman vortices) are proposed, based on which a new model is proposed to predict the TKE in vegetated regions. The reasonable performance of this new model, compared with previous research data, indicates the feasibility of the new formula and associated theoretical hypotheses.