Velocity Analysis of a Flow Passing over a Vegetated Slope

A sheet flow or overland flow is simulated by the theory of laminar flow passing over a grassed slope with wood. The flow region is divided into two layers (vegetation layer & soil layer) or three layers (wood layer, vegetation layer & soil layer) according to the water depth. The Navier-Stokes equations are employed to govern the flow in the wood layer, and the Biot's theory of poro-elasticity is applied to delineate the flow in the vegetation and soil layers. These equations are simplified, modified and nondimensionalized under different vegetation situations, and then solved analytically. As a result, the velocity distributions are derived by a semi-analytical approach to understand the flow mechanism.一般坡地上除了草地以外，尚有木本植物，因此模擬植生坡面上之薄層流 (或稱為漫地流)，需同時探討種植木本植物與草本植物之植生坡面，本研究依水深將流場劃分為兩層或三層，分別為植生層、土層兩層，或木本層、植生層和土層三層。木本層之控制方程式是以Navier-Stokes 方程式加上木本植物對水流造成的阻力來描述；植生層與土層之控制方程式則以Biot孔彈性介質理論為基礎，依不同的植生狀態加以修正、無因次化和以半解析的方式針對垂直流速分布進行求解