基于SCHISM模型的三维两相浑水模型研究

Development of three-dimensional two-phase mixture model based on SCHISM

传统水沙模型多采用雷诺平均方程结合含沙量对流扩散方程,并用纯水紊流模型进行封闭。这类模型无法考虑固、液相间作用,在含沙量较大、颗粒粒径较粗时会产生误差。文章采用两相浑水紊流模型对两相浑水基本方程进行封闭。两相浑水理论将固、液两相流看作一个整体,但考虑了固、液相间作用和颗粒碰撞等微观物理机理,而且偏微分方程的数量和形式与传统水沙模型中的基本方程相同,方便将两相浑水理论嵌入至已有的水沙模型中,并应用于河流、湖泊和河口等大尺度水沙流动模拟。首先对两相浑水理论进行梳理,将其转化为三维水动力学模型SCHISM控制方程的形式并嵌入至SCHISM模型中,最终将其应用在经典的二维明渠恒定、均匀流实验、深槽实验和2012年黄河花园口至艾山段洪水过程的三维数值模拟。

Classical fluvial models usually describe suspended sediment-laden flows by directly borrowing the Reynolds equations from the fluid dynamics that are limited to single-phase flows and adding an advection-diffusion equation to calculate suspended load transport. Such models lack the capability of modeling the complicated mechanisms of interphase interaction and particle collisions, thereby suffering from too large prediction errors in the case of large particle sizes or high concentration. A two-phase mixture model is adopted in this study to investigate sediment-laden flows, consider solidliquid flows as an integrity, and simulate interphase interactions and particle collisions. This new model takes a form very similar to the classical fluvial model, and hence it is easy to insert it in an existing code and apply to practical cases. This paper first summarizes its basic equations, and then recasts them in the form of the SCHISM governing equations for 3 D hydrodynamic modeling. Finally, we apply our twophase mixture model to simulations of fully-developed steady uniform open channel flows, trench observations, and a 2012 real flood event in the Huayuankou-Aishan reach of the Yellow.