分层环境中异重流运动问题的直接数值模拟

为了研究线性分层环境下的开闸式异重流运动过程的问题，采用改进的高精度直接数值模拟（DNS）模型，在正交坐标系下，以DNS为基本求解器，实现物质运输方程和Navier-Stokes方程同步求解.采用距离函数平滑初始状态的不连续运输方程，利用具有六阶精度的迎风紧致差分格式（UCCD）改进原模型，更准确地求解物质输运方程.通过求解一维对流方程和入侵重力流的模拟结果验证了模型的可靠性.开展泥沙异重流与线性分层环境掺混过程的研究，并获得了高精度数值结果，可以更好地捕捉中间入侵的异重流产生的内波效果.结果表明：该模型不仅可以准确模拟入侵异重流卷吸分层环境水体的过程，还可以准确模拟头部运动位置、异重流卷吸沉降以及能量转换等问题.
Abstract: The improved direct numerical simulations (DNS) with high-resolution numerical model was employed to simulate lock-exchange gravity current in a linearly stratified ambient fluid. The model was established in the Cartesian coordinate system, using DNS as the base solver to make material transport equation and the Navier-Stokes equation solved simultaneously. The distance function was used to smooth the initial discontinuous transport equation. The upwind compact difference scheme (UCCD) with the sixth-order accuracy was used to improve the original model and solve material transport equation more accurately. The reliability of the model was verified by solving the simulation results of the one-dimensional convection equation and the invasion gravity current. The process of mixing the sediment gravity current and linear stratification ambient fluid was studied. High-precision numerical results are obtained and internal wave generated by intrusion of gravity current is better captured.Results show that the model can accurately simulate stratification ambient fluid entrained by invasion gravity current and thefront movementlocation of turbidity currents. Sedimentation rates and energy conversion are embodied excellently.