AI 中文总结
研究钝体尾流全局稳定性分析，用基于有限差分离散化的矩阵形成方法，评估多种流出边界条件，发现罗宾条件能在截断域内实现全局模态稳健收敛，提高分析效率，凸显该方法在复杂稳定性分析中的适用性。
AI 中文摘要
使用基于有限差分离散化的矩阵形成方法对钝体尾流进行全局线性稳定性分析。特别强调流出边界条件的影响，目的是在不降低精度或在出口附近产生虚假振荡的情况下最小化所需的计算域大小。本研究聚焦于圆柱和大攻角翼型等钝体后的不可压缩尾流，特别是在全局模态呈现下游空间放大的区域。结果表明，在临界雷诺数以下，即使尾流几乎不存在，显著的空间增长仍可在下游持续很远。这凸显了在出口处施加物理边界条件的重要性。评估了几种常用的流出边界条件，结果表明，对于不同的雷诺数情况，罗宾条件能在大幅截断的域内实现全局模态的稳健收敛，从而提高全局稳定性分析的效率。这些发现突出了矩阵形成方法在复杂稳定性分析中的更广泛适用性。
英文摘要
Global linear stability analysis of bluff body wake flows is performed using the matrix-forming method based on finite-difference discretization. Particular emphasis is placed on the influence of outflow boundary conditions, with the aim of minimizing the required computational domain size without degrading accuracy or inducing spurious oscillations near the outlet. This study focuses on incompressible wakes behind bluff bodies such as cylinders and airfoils at high angle of attack, especially in regimes where global modes exhibit downstream spatial amplification. It is shown that below the critical Reynolds number -- where the global mode remains linearly stable -- significant spatial growth can persist far downstream, even when the wake is nearly absent. This behavior underscores the importance of imposing a physical boundary condition at the outlet. Several commonly used outflow boundary conditions are evaluated, including Dirichlet, Neumann, extrapolation, stress-free, sponge layer, and the Robin condition that incorporates predictions from local linear stability analysis at the outlet. The results demonstrate that, for different $Re$ cases, the Robin condition enables robust convergence of global modes within substantially truncated domains, thereby improving the efficiency of global stability analysis. These findings highlight the broader applicability of the matrix-forming approach for complex stability analyses, including Floquet analysis of time-periodic flows and extensions to compressible configurations.
Journal refJ. Comput. Phys., 565, 115191 (2026)
