RESED3D模式在水庫泥砂運移模擬應用之探討

Abstract

本研究之主要目的係擬探討RESED3D在水庫泥砂運移的模擬應用上可能存在之關鍵問題。 RESED3D模式係架構在垂直水平分離演算(VHS)之概念，在座標系統上，水平方向與垂直方向分別採用正交曲線座標系統與 座標系統，水理模式先由深度平均控制方程式求解水平二維每個計算格點之水面高程以及水深平均流速，將之代入流速差異量方程式，求得三維每個計算格點相對於水深平均流速之流速差異量，求解出三維空間上每個計算格點之流速分佈。沉滓運移模式分為三維質量傳輸方程式、作用層連續方程式及底床載連續方程式。依據該架構，數值上邊界條件之設定會是問題之一；泥沙運移機制上，沉降速度及擴散係數會是另一項關鍵，針對此議題，研選實驗與石門水庫案例作為測試對象，並加以解析探討其影響。

This study aims to investigate the key issues that the RESED3D model might pose in the reservoir sediment transport applications. The RESED3D model is developed based on a vertical-horizontal splitting (VHS) method used in this study. By following the vertical and horizontal splitting concept, the shallow water flow governing equations were split into two parts including the depth-averaged 2D equations and velocity defect equation in vertical direction. The depth-averaged 2D equations were transformed into orthogonal curvilinear coordinate system to solve the elevation of every water column and depth-averaged velocities. The velocity defect equations can be derived by subtracting the 2D depth-averaged equations from the 3D Navier-Stokes equations. Incorporated with the continuity equation, the three-dimensional velocity field can therefore be solved.; the empirical suspended-load, active-layer and bed-load formulae with concentrated for the sediment transport computation. According to this structure, the setting of boundary conditions will be one of the key issues. Moreover, in sediment transport mechanisms , settling velocity and diffusion coefficient will be another key issue. Several experiments of the Shihmen Reservoir physical model are selected as test cases and to investigate their influences on the key parameters.