海底大弯曲渠道中浊流的三维数值模拟

Three-dimensional Numerical Simulation of Turbidity Current in the High Sinuous Submarine Channel

因和海洋油气资源的密切关系,对浊流在海底弯曲渠道中的流动及沉积的研究一直为研究热点之一。本研究采用内插法产生正交性高的网格和基于雷诺平均的Navier-Stokes方程及浮力项修正的湍流k-ε模型对高弯曲度梯形渠道内及漫滩的浊流进行了三维数值模拟,得到大弯曲度渠道中浊流流动、沉积及二次流的如下特征:周围流体的夹带作用强,弯道顶点断面处的密度等值面的倾斜度随着弯曲度的增加而增加;浊流多次流动后内岸处有较多侵蚀,渠道内沉积呈现由内岸向外岸的波状倾斜;从紧贴弯曲渠道边缘的纵剖面上观察的沉积比低弯曲度的更加波状起伏;从切过渠道内部及堤坝的纵剖面上观察的沉积比低弯曲度渠道更呈明显的由上游向下游方向倾斜及厚度减低的特征;渠道底部的外岸处存在受较大压缩的类似河流的二次流。

Research on the flow and deposition of turbidity currents in submarine channels is one of the hot topics due to its close relation with hydrocarbon resources. It is presented here a three-dimensional numerical simutation of turbidity currents within a trapezoidal channel with high sinuosity based on Reynolds-averaged Navier-Stokes equations and buoyancy modified k-ε turbulence model. A high orthogonal of grid is generated by interpolation to avoid too much skew from the sinuosity of the channel. The following characteristics concerning the flow, and sedimentation of turbidity currents in high sinuous channel are found: strong entrainment of surrounding fluid, incline of isosurface of density at the bend apex increases with sinuosity; at bend apex cross section, erosion appears at the inner bank and bed deposits present a wavy tilt to the outer bank; the longitudinal profile by the edge of bend apex is more wavy than that for low sinuous channels; the longitudinal profile cutting through part of the channel shows that thicker channel bed deposit is intersected by arch-shapered thinner bank deposit and the profile dips more to the downstream; river- like secondary flow is more pressed at the outer bed corner of channel bend apex.