Non-Hydrostatic Modeling of Vegetation Effects on Wave and Flow Motions

A three-dimensional, non-hydrostatic model is developed to study the effects of aquatic vegetations on wave and flow motions. Vegetation is modeled as resistance that is introduced as drag force in the momentum equations and drag-induced turbulence production in the turbulence equations. In addition effects of vegetation are incorporated into the model with a generic turbulence length scale approach to allow for conversion among several popular turbulence schemes. The model is first applied to examine dispersive waves through emergent vegetation. Consistent with previous studies, it is found that wave height decays as density of vegetation increases. The model is then applied to examine flows through submerged and emergent vegetations. In the case of one-dimensional flow over submerged vegetation, model results show that the flow is retarded inside the vegetation layer and a maximum turbulent intensity occurs at the top of vegetation. For the case of emergent vegetation in a 2-D open channel flow, the model results successfully capture the lateral variation of mean flow, turbulence, and free-surface fluctuations, in comparison with observations. Moreover, the horizontal large eddies (HLEs), responsible for intense lateral momentum exchanges, are apparent at the lateral boundary between the vegetation zone and free stream zone. The period of HLEs predicted by the model matches the one using the linear stability analysis. Overall this new non-hydrostatic model allows for simulating both wave and flow motions affected by vegetation. In particular non-hydrostatic modeling provides a framework to study dispersive wave over vegetations in the future.