輸砂公式對多方式特性法數值模擬之影響

Abstract

本模式屬於結合演算(coupled)模式，可同時求解水流及輸砂方程式；係以李氏(1992)、Yeh et al.(1995)所發展之非均勻質多方式特性法模式為基礎，再加以改良者。本模式採用較具物理意義之特性法(method of characteristics)，引進緩衝段法(buffer reach method)之概念，考慮護甲(armor)作用及交換層(mixing layer)厚度之改變，修正遮蔽因子(hiding factor)或顯露因子(exposure factor)之效應；為了檢驗模式之準確性與適用性，採用Suryanarayana(1969)實驗與台大水工試驗所顏等(1988、1990)之A組實驗案例，選擇不同輸砂公式計算輸砂量，探討淤積及沖刷情況下，底床高程及特性擾動波之變化情形，並加以比較分析。根據模擬結果，選用不同輸砂公式對底床沖淤量及床質粒徑篩分波速有頗大之影響。

The proposed model is a coupled model in which the flow and sediment transport equations are solved simultaneously. It is an extension of the non-uniform sediment multimode characteristics model developed by Lee(1992) and Yeh et al. (1995). In the model, several features are considered: physics-based method of characteristics, buffer reach concept, armor effect, change of mixing layer, and hiding or exposure factor. To verify the accuracy and the applicability of the model, Suryanarayana’s (1969) and Yen et al.’s (1988 & 1990) experimental data are adopted. Several sediment transport formulas are selected to test their effects on the bed evolution and characteristics waves for flows in aggrading and degrading channels. According to the numerical results, selection of different sediment transport formulas will significantly affect the amount of scour or deposition and the associated sorting waves of the bed material.