Author(s): Wang Lingling; Zhong Na; Zheng Shengyi
Linked Author(s): Lingling Wang
Keywords: Large eddy simulation; Momentum jet; Multi-grid method
Abstract: Many industrial and environmental effluent discharges into water environment can be categorized as jets in the ambient water. It is important to study and quantify the mixing of the discharge so that an accurate environmental impact assessment can be made for such discharge condition. In the paper, plane jet in environment with unsteady flows and wave motion is studied by using multi-grid method. Numerical model based on the full Navier- Stokes equations is developed under the concept of large eddy simulation. The operator splitting method developed by Li and Lin (2001, 2003) is employed to solve the modified NSE. Multi-grid method with four-color Gauss-Seidel relaxation combining with 7-point finite difference scheme is adopted to solve the propagation step. Convergence rate of multi-grid is about 0. 42 for the jet with wave and 0. 49 for pure jet. The numerical results show wave enhances the mixing of the jet with the ambient fluid, and cause a periodic deflection of jet. The spreading characterize constant α are 0. 105 and 0. 147 for pure jet and jet in wave respectively, the result is in good agreements with the data obtained by Andreoppulos et al. (1986) and Kuang and Hsu (1998). Numerical results are compared to that obtained by Gauss-Seidel iteration method and Jacobi iteration. The CPU time needed by multi-grid method is only around 76% and 54% of the time needed by previous two iteration methods respectively. The model is verified high efficiency with satisfied convergence speed.
Year: 2005