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首页> 外文期刊>International Journal of Heat and Fluid Flow >A DNS/URANS approach for simulating rough-wall turbulent flows
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A DNS/URANS approach for simulating rough-wall turbulent flows

机译：用于模拟粗糙壁湍流流动的DNS / urans方法

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摘要

A novel hybrid method combining direct numerical simulation (DNS) and the Reynolds-averaged Navier Stokes (RANS), denoted as a stress-blended method (SBM), has been developed. The SBM is targeted at simulating turbulent flows over arbitrary rough surfaces in which computational savings can be achieved by making the DNS domain as small as possible. Within the SBM framework, a RANS model is enforced above the roughness layer to prevent the momentum build-up which arises in simulations where the computational domain is too small to represent the largest eddies. The SBM is validated for turbulent channel flow, both for smooth wall turbulence and using a parametric forcing approach to mimic roughness effects, with a computational cost that scales linearly with Re-tau. The method is then applied to selected subsets of a scanned grit-blasted surface. For the same subset, the roughness function is found to be within 1% of available DNS. Comparisons of small and large subsets showed differences of over a factor of two in equivalent sand grain roughness, indicating the importance of choosing representative surface samples. Simulations in the fully rough regime are carried out using one to two orders of magnitude fewer points than in a typical DNS. Since no assumptions on the roughness properties or the flow structure (such as outer layer similarity) are made, we expect the SBM to be applicable to non-equilibrium turbulent boundary layer flows.
机译：已经开发了一种新颖的混合方法，结合了直接数值模拟（DNS）和雷诺平均的Navier Stokes（RANS），其表示为应力混合方法（SBM）。 SBM在模拟湍流上瞄准任意粗糙表面，其中可以通过使DNS域尽可能小来实现计算节省。在SBM框架内，RAN模型在粗糙度层上方强制执行，以防止在计算域太小以代表最大漩涡的模拟中产生的动量积累。 SBM验证用于湍流通道流，用于光滑的壁湍流，并使用参数化强制方法来模拟粗糙度效应，具有与RE-TAU线性缩放的计算成本。然后将该方法施加到扫描的砂砾表面的选择子集。对于相同的子集，发现粗糙度函数在可用DNS的1％范围内。小型和大亚群的比较显示出在等效​​砂粒粗糙度中两倍的差异，表明选择代表性表面样品的重要性。完全粗糙的制度中的模拟是使用比典型DNS中的一个到两个数量级的数量级进行。由于没有对粗糙度性能或流动结构（例如外层相似性）的假设，因此我们希望SBM适用于非平衡湍流边界层流动。

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