Most studies of vortex shedding from a circular cylinder in a gas flow have explicitly or implicitly assumed that the no-slip condition applies on the cylinder surface. To investigate the effect of slip, vortex shedding is simulated using molecular gas dynamics (the direct simulation Monte Carlo method) and computational fluid dynamics (the incompressible Navier-Stokes equations with a slip boundary condition). A Reynolds number of 100, a Mach number of 0.3, and a corresponding Knudsen number of 0.0048 are examined. For these conditions, compressibility effects are small, and periodic laminar vortex shedding is obtained. Slip on the cylinder is varied using combinations of diffuse and specular molecular reflections with accommodation coefficients from zero (maximum slip) to unity (minimum slip). Although unrealistic, bounce-back molecular reflections are also examined because they approximate the no-slip boundary condition (zero slip). The results from both methods are in reasonable agreement. The shedding frequency increases slightly as the accommodation coefficient is decreased, and shedding ceases at low accommodation coefficients (large slip). The streamwise and transverse forces decrease as the accommodation coefficient is decreased. Based on the good agreement between the two methods, computational fluid dynamics is used to determine the critical accommodation coefficient below which vortex shedding ceases for Reynolds numbers of 60–100 at a Mach number of 0.3. Conditions to observe the effect of slip on vortex shedding appear to be experimentally realizable, although challenging.

中文翻译：

---

滑移对气流中圆柱体涡旋脱落的影响

大多数关于气流中圆柱体涡旋脱落的研究都明确或隐含地假设无滑移条件适用于圆柱体表面。为了研究滑移的影响，使用分子气体动力学（直接模拟 Monte Carlo 方法）和计算流体动力学（具有滑移边界条件的不可压缩 Navier-Stokes 方程）来模拟涡旋脱落。雷诺数为 100，马赫数为 0.3，相应的克努森数为 0.0048。对于这些条件，可压缩性影响很小，并且会获得周期性层流涡旋脱落。圆柱体上的滑移使用漫反射和镜面分子反射的组合变化，调节系数从零（最大滑移）到统一（最小滑移）。虽然不切实际，还检查了反弹分子反射，因为它们近似于无滑移边界条件（零滑移）。两种方法的结果都具有合理的一致性。随着调节系数的降低，脱落频率略有增加，并且在低调节系数（大滑动）时脱落停止。顺向力和横向力随着调节系数的减小而减小。基于两种方法之间的良好一致性，计算流体动力学用于确定临界调节系数，低于该系数时，雷诺数为 60-100，马赫数为 0.3 时涡旋脱落停止。观察滑移对涡旋脱落影响的条件似乎可以通过实验实现，尽管具有挑战性。