Investigation Of The Vegetation Flow Using Porous Medium Model

Flow through and around vegetation,seen as the flow through porous medium,can be described by a porous flow model which has been verified applicable and efficient in simulating the flow affected by vegetation.This research focuses on simulating vegetation flow by specifying spatial varying solid volume fraction using house in codes CFD model coupled with porous medium model.The CFD model is based on the shallow water model with hydrostatic pressure assumption.The free surface is captured by the vertical coordinate transformation method.The vegetation domain is treated as porous medium by specifying the spatial variable porosity.The simulation results are in good agreement with experiments in the literature in terms of turbulence intensity and velocity distribution,which verifies the accuracy of the porous medium model.The comparisons indicate that the model works well for the macroscopic simulation of vegetation flow including the flow characteristics in the wake.Furthermore,compared with the multi-body model,the porous medium model shows higher computational efficiency with the simulation accuracy being guaranteed,therefore can be further applied to investigate the large-scale vegetation flows.On this basis,the model is applied to study the flow around single porous obstruction and two porous obstructions arranged in tandem.The analysis of flow around the single porous obstruction focus on the distribution about lateral velocity and flow velocity,and instantaneous fluctuating velocity,wake structures and bed shear stress.The results of the two porous obstructions arranged in tandem mainly involve the lateral velocity and flow velocity,the instantaneous fluctuating velocity,the wake structures,and the vortex frequency.It is shown that the distance between the two porous obstructions and the solid volume fraction have an impact on the hydrodynamic characteristics of the flow field.In addition,only a dominant vortex frequency can be detected in the flow field,so that there is only one Strouhal number.