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Analysis of Withdrawal Condition and Equilibrium Depth of Stratified Flow by 2-D Vertical Numerical Model

Author(s): Chien-Jung Liu; Shaohua Marko Hsu; Ching-Biao Liao

Linked Author(s): Shaohua Marko Hsu

Keywords: Bottom density currents; 2nd order upwind scheme; Equilibrium thickness

Abstract: In Taiwan, intensive rainfall by Typhoon brings large portion of eroded sediment from watershed into reservoirs and forms turbidity currents. Peak discharge and high concentration provides turbidity currents with energy to reach the dam site and forms muddy lake afterward. For obtaining clear water from a reservoir, the equilibrium height of the muddy lake surface could be used to evaluate the quantity of muddy water withdrew from outlet. In this study, a vertical two-dimensional model using finite-difference method with MAC staggered-grid system, large eddy Simulation method (LES), and 2nd order upwind scheme is used to simulate the withdrawal phenomenon of bottom density currents. By comparison in variation of outflow concentration and lower-layer equilibrium thickness between numerical and experimental results, the model is verified and numerical experiments were performed. The numerical critical Richardson number calculated by numerical result is larger than our experimental results (Yu, 2004) but closer to other authors’ previous study.


Year: 2007

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