Numerical study on turbulent flow and honami in and above flexible plant canopy

Abstract The waving of flexible plant termed honami is caused by large-scale vortices which are induced by inflectional instability of flow field. The movement of plant in turn may affect the turbulent flow field via resistance to flow, turbulence production and dissipation. The present study treats the interaction of turbulent flow and honami employing 2D-LES, in which a concept of “plant grid” is used to treat the movement of plant in addition to the ordinary LES grid. The drag due to the plant is formulated in proportion to the square of the relative velocity between flow and motion of plant in momentum equations for turbulent flow field. In transport equation of turbulent energy, the additional terms of turbulent production and dissipation due to motion of plant are included. The computational result indicates that the honami reduces the periodicity of vortex generation, and the velocity fluctuation, therefore, becomes irregular if compared with the case for which the plant is assumed to be rigid. It was also found that the honami repeats generation and disappearance.