非线性波作用下非对称沙纹床面流场特性数值分析

Numerical analysis of characteristics of fluid field over asymmetric rippled bed under nonlinear wave

海床上的沙纹对泥沙输运和波浪衰减有着重要的影响.通过数值波浪水槽研究了非线性波作用下非对称沙纹床面底层的流动特性.控制方程为雷诺时均方程和k-ε紊流模型.入射波为椭圆余弦波,采用PLIC-VOF法追踪自由表面.通过数值模拟得到了不同波浪条件下的瞬时速度场和涡量场.计算结果表明:非线性波作用下,非对称沙纹床面两侧的涡动强度不相等,涡量值与波浪参数密切相关;波浪非线性增强,涡量值增大,最大涡量值对应的相位角减小;涡量值大小的变化与外流场速度变化不同步达到最大,随着Ursell数增大,涡量值在小相角下达到最大值.

Ripples are dumping and sediment common features in offshore coastal transport. The distributions of the areas, and they are flow fields induced important for wave by nonlinear water waves near a natural asymmetric rippled bed are investigated by absorbed numerical wave tank. The gover wave ning mak equations are Reynolds time-averaged equations and two equation κ-ε model. A piston-type er is set up in the computational domain to produce incident cnoidal waves and the free surface is traced through the PLIC-VOF （piecewise linear interface construction-volume of fluid）. A complete process of vortex formation, evolvement and disappearance was observed by the numerical model. By analyzing the circulation and trajectory of vortices with varied phases, the influences of wave characteristics on the flow closed to the asymmetric ripple beds have been carried out. The numerical results indicate that the wave parameters determine the characteristics of vortex field. With the nonlinearity improved, the vortex intensity becomes stronger. It reaches their maximum value shortly after the free stream velocity begins to decelerate. The vortex and the wave velocity reach their maximum values at different time. With the increasing of Ursell number, vortex value reaches its maximum value at small phase angle.