A numerical study of stably stratified flows past spheres at Reynolds numbers $Re=200$ and $Re=300$ is reported. In these flow regimes, a neutrally stratified laminar flow induces distinctly different near-wake features. However, the flow behaviour changes significantly as the stratification increases and suppresses the scale of vertical displacements of fluid parcels. Computations for a range of Froude numbers $Fr\in [0.1,\infty ]$ show that as Froude number decreases, the flow patterns for both Reynolds numbers become similar. The representative simulations of the lee-wave instability at $Fr=0.625$ and the two-dimensional vortex shedding at $Fr=0.25$ regimes are illustrated for flows past single and tandem spheres, thereby providing further insight into the dynamics of stratified flows past bluff bodies. In particular, the reported study examines the relative influence of viscosity and stratification on the dividing streamline elevation, wake structure and flow separation. The solutions of the Navier-Stokes equations in the incompressible Boussinesq limit are obtained on unstructured meshes suitable for simulations involving multiple bodies. Computations are accomplished using the finite volume, non-oscillatory forward-in-time (NFT) Multidimensional Positive Definite Transport Algorithm (MPDATA) based solver. The impact and validity of the numerical approximations, especially for the cases exhibiting strong stratification, are also discussed. Qualitative and quantitative comparisons with available laboratory experiments and prior numerical studies confirm the validity of the numerical approach.

雷诺数下流过球体的稳定分层流的数值研究 $\mathrm{[R}Ë=200$ 和 $\mathrm{[R}Ë=300$被报道。在这些流动状态下，中性分层的层流引起明显不同的近流特征。但是，流动行为会随着分层的增加而发生显着变化，并抑制流体包裹的垂直位移规模。一系列Froude数的计算$F\mathrm{[R}\in [0.1，\infty ]$结果表明，随着弗洛德数的减少，两个雷诺数的流型变得相似。雷电波不稳定性的典型模拟$F\mathrm{[R}=0.625$ 和二维涡流在 $F\mathrm{[R}=0.25$说明了流过单个球体和串联球体的流态，从而提供了对通过钝体的分层流动力学的进一步了解。特别是，已报道的研究检查了粘度和分层对分流线高程，尾流结构和流动分离的相对影响。不可压缩的Boussinesq极限中的Navier-Stokes方程的解是在适用于涉及多个物体的模拟的非结构化网格上获得的。计算是使用基于有限体积，无振荡的时间前向（NFT）多维正定传输算法（MPDATA）的求解器完成的。还讨论了数值近似的影响和有效性，尤其是对于表现出强烈分层的情况。