水深对沙波紊流特性影响的数值分析

Numerical analysis of water depth effect on turbulence over dunes

运用FLUENT软件雷诺应力紊流模型(RSM)及SIMPLEC算法,对不同水深下沙波紊流特性进行数值模拟分析,模拟结果与实测结果吻合良好。在此基础上对4种不同相对水深下纵、垂向流速、压强及雷诺切应力分布规律进行研究。研究结果表明:相对水深较大时紊流特性受沙波地形影响较小,只有近底水体受沙波作用;相对水深较小时整个水体都会受到影响。在沙波尺度不变的条件下,紊流强度一般随水深的增加而减小,不同位置处的沙波紊流特性受水深影响程度及变化规律均不同。最大压强水平位置受水深影响的变化规律与再附点基本一致,可将最大压强作为再附点位置的判断依据。

The objective of this paper is to study the effect of water depth on the flow over a train of two-dimen-sional dunes, focused on vertical velocity, Reynolds stress and turbulent kinetic energy distribution. A mathematicalmodel based on the Reynolds-Averaged Navier-Stokes（RANS） equations, Reynolds stress turbulence（RSM） closureand SIMPLEC algorithm is adopted to describe this complex phenomenon, with simulated results agreed well withmeasured ones. The numerical results show that turbulence parameters are affected by the relative depth： the pro-files of turbulence parameters collapse onto a single curve in the outer region, with the near-bed affected by thedunes at larger depths; dune topography governs the entire water at a shallower depth. It is obvious that the turbu-lence intensity decreases with increasing water depth and flow characteristics affected by water depth are differentdue to positions. Location of maximum pressure affected by depth is consistent with the reattachment point, indicat-ing that maximum pressure can be treated as the criterion of reattachment length.