Title: A sensor-restrained artificial shear diffusivity for large-eddy simulations of vortex-dominated compressible flows Show Chinese title

Title: 针对旋涡主导的可压缩流动的大涡模拟的传感器限制的人工剪切扩散性

Abstract: We propose a sensor-restrained model for the shear viscosity term within the localized artificial diffusivity (LAD) scheme to stabilize compressible large-eddy simulations with low-pressure-core vortical structures. LAD methods are used in numerical solvers based on spectral-like compact finite-difference schemes. While high-order-accurate numerical schemes with proper discretization guarantees physical fidelity, the LAD role is to suppress non-physical oscillations arising in compressible flow simulations near shock waves and other sharp gradients. LAD is a cost-effective approach which adds artificial shear and bulk viscosities, and thermal conductivity to their physical counterparts. However, an unrestricted added diffusivity may lead to poorly-resolved coherent structures and undesirable turbulence statistics. In order to prevent excessive numerical diffusion in compressible shear flows, the artificial shear viscosity term can be disabled in cases where the simulation is already stable. However, in flow simulations where vortices emerge within a low-pressure region, a strong pressure decay may lead to instabilities that make the simulation unstable. For such cases, adding artificial shear viscosity is necessary to maintain numerical stability, as this issue is unaddressed by the artificial bulk viscosity and thermal conductivity alone. Our approach integrates a sensor into the standard LAD formulation, particularly in the artificial shear viscosity, that reduces the added diffusivity while preserving numerical stability. This advancement is possible by adding the shear diffusivity only in localized flow regions consisting of low-pressure-core vortices, and it enables stable and accurate large-eddy simulations (LES) of compressible vortex-dominated flows, such as those encountered in separated flows and bluff-body wakes. Show Chinese abstract

Abstract: 我们提出了一种传感器限制模型来处理局部人工扩散（LAD）方案中的剪切粘度项，以稳定具有低压核心涡旋结构的可压缩大涡模拟。 LAD方法被用于基于谱类紧致有限差分方案的数值求解器中。 尽管高精度数值格式在适当的离散化下保证了物理保真度，但LAD的作用是抑制可压缩流模拟中激波和其他陡峭梯度附近出现的非物理振荡。 LAD是一种成本效益高的方法，它向物理粘度和热导率添加了人工剪切粘度和体积粘度。 然而，无限制地添加扩散可能会导致分辨率较差的相干结构和不理想的湍流统计。 为了防止可压缩剪切流中过多的数值扩散，在模拟已经稳定的情况下可以禁用人工剪切粘度项。 然而，在流动模拟中，当涡旋出现在低压区域时，强烈的压力衰减可能导致使模拟变得不稳定的不稳定性。 对于这种情况，需要添加人工剪切粘度以维持数值稳定性，因为仅靠人工体积粘度和热导率无法解决这个问题。 我们的方法将一个传感器集成到标准LAD公式中，特别是在人工剪切粘度中，这减少了添加的扩散同时保持数值稳定性。 通过仅在包含低压核心涡旋的局部流动区域内添加剪切扩散，这一进展成为可能，并且能够实现可压缩涡旋主导流的大涡模拟（LES），例如在分离流和钝体尾流中遇到的情况。