潮流数值模拟中紊动粘性系数的研究

A Study on Eddy Viscosity Coefficient in Numerical Tidal Simulation

从流体运动基本方程出发 ,对Boussinesq假设的合理性进行了初步探讨 ,阐述了紊动粘性系数的物理含义及其在数值计算中所起的作用 .就一内设正交丁坝的半封闭海域中的平面紊动粘性系数对二维潮流数值计算结果的影响进行了讨论 .结果表明 ,平面紊动粘性系数对潮位和平均流速的影响较小 ;随着紊动粘性系数的增加 ,丁坝背流侧回流的强度和影响范围均明显增大 .就风生流和环岛水流两个理论算例中的垂向紊动粘性系数对三维潮流数值计算结果的影响进行了讨论 .结果表明 ,垂向紊动粘性系数越大 ,流速分层越不明显 ,流速的绝对值也越小 ;垂向紊动粘性系数的梯度变化则对水平流速的垂向分布起着决定性的作用 .综合理论分析和数值试验的成果 ,垂向紊动粘性系数宜采用抛物线分布的结构型式 .

On the basis of fluid motion equations,the rationality of the Boussinesq hypothesis is discussed,and the physical meaning of the eddy viscosity coefficient and its function in numerical simulation are described.A semi enclosed rectangular sea area,with an orthogonal spur dike is designed for the analysis of the effect of horizontal eddy viscosity coefficient( A H ) on 2 D numerical tidal simulation.The calculated results show that A H has little influence on the tidal level and the average flow velocity;however,with the increase of A H ,the intensity of return flow near the spur dike and its affecting range increase correspondingly.The calculation of a wind induced current and an annular current are taken as examples for analysis of the influence of the vertical eddy viscosity coefficient( A V ) on 3 D numerical tidal simulation.The calculated results show that the absolute value of A V is inversely proportional to that of horizontal velocity,and the vertical gradient value of A V determines the vertical distribution of horizontal velocity.According to numerical tests and theoretical analysis,the parabolic pattern of distribution of A V is recommended.