Vortical structures and wakes of bluff bodies in homogenous and stratified environment are common and important in ocean engineering. Based on the Boussinesq approximation, a thermocline model is proposed to deal with the variable density stratified fluid, and implemented in the commercial software Simcenter STAR-CCM+ framework. The improved delayed detached eddy simulation (IDDES) modeling method is adopted to resolve the coherent vortical structures and turbulent wakes precisely and efficiently. Four conditions consisting of one homogenous and three stratified fluid cases with different density gradient past a sphere at Reynolds number 3 700 are investigated. Results show that density stratification has a great impact on the vortical structures, the vertical motion is suppressed and internal waves will be induced and propagated, which is very different with that of homogenous situation. With the stratification strength increases, the vortical structures are gradually flattened, the asymmetry and anisotropy between vertical and horizontal motions are enhanced.

在均匀和分层的环境中，虚张声势的漩涡结构和尾流在海洋工程中很常见，也很重要。基于Boussinesq近似，提出了一种用于处理变密度分层流体的温床模型，并在商业软件Simcenter STAR-CCM +框架中实现。采用改进的延迟分离涡模拟（IDDES）建模方法，可以精确高效地求解相干涡结构和湍流。研究了四个不同的条件，这些条件包括一个均匀的和三个分层的流体情况，这些情况通过雷诺数3 700的球体具有不同的密度梯度。结果表明，密度分层对旋涡结构有很大的影响，垂直运动受到抑制，内部波将被诱发和传播，这与同质情况大不相同。随着分层强度的增加，涡旋结构逐渐变平，垂直运动和水平运动之间的不对称性和各向异性得到增强。