论文标题
层流和过渡流的动力学在滑动表面上：对层流腹部分离的影响
Dynamics of laminar and transitional flows over slip surfaces: effects on the laminar-turbulent separatrix
论文作者
论文摘要
通过直接数值模拟研究了滑动表面对平面poiseuille流动流动层的层状分离的影响。湍流寿命是湍流的持续的可能性，研究了具有各种滑动长度的过渡流。与无滑动情况相比，滑动表面降低了持续湍流的可能性，并且随着滑动长度的增加，可能性进一步降低。对滑动表面对湍流过渡到湍流的影响的确定性分析是使用非线性行驶波解决方案对Navier-Stokes方程进行的，也称为精确的相干溶液。使用两个溶液家族，称为P3和P4，因为它们的下支流溶液嵌入了层流和湍流的吸引盆地的边界（Park＆Graham 2015）。此外，它们表现出不同的流量结构 - P3和P4分别表示为核心模式和临界层模式。滑动表面对溶液的明显影响通过皮肤摩擦的演化，线性生长速率和过渡轨迹的相位投影观察到。滑动表面对核心模式几乎没有修改过渡动力学，但对于临界层模式而言大多数。最重要的是，滑动表面促进了不同的过渡动力学 - 核心模式的早期和旁路样过渡以及临界层模式的延迟和h-/k型的过渡。基于时空和象限分析，发现滑动表面促进了靠近通道中心的涡流核心附近的强壁式运动（类似扫除事件）的普遍性，从而引起了早期过渡，而持续的弹射事件则在$λ$ - 所示的涡流核心的区域中存在于关键层接近延迟的延迟。
The effect of slip surfaces on the laminar-turbulent separatrix of plane Poiseuille flow is studied by direct numerical simulation. Turbulence lifetimes, the likelihood that turbulence is sustained, is investigated for transitional flows with various slip lengths. Slip surfaces decrease the likelihood of sustained turbulence compared to the no-slip case, and likelihood is further decreased as slip length is increased. A deterministic analysis of the effects of slip surfaces on transition to turbulence is performed using nonlinear traveling wave solutions to the Navier-Stokes equations, also known as exact coherent solutions. Two solution families, dubbed P3 and P4, are used since their lower-branch solutions are embedded on the boundary of the basin of attraction of laminar and turbulent flows (Park & Graham 2015). Additionally, they exhibit distinct flow structures -- the P3 and P4 are denoted as core mode and critical layer mode, respectively. Distinct effects of slip surfaces on the solutions are observed by the skin friction evolution, linear growth rate, and phase-space projection of transitional trajectories. The slip surface modifies transition dynamics little for the core mode, but considerably for the critical layer mode. Most importantly, the slip surface promotes different transition dynamics -- early and bypass-like transition for the core mode and delayed and H-/K-type-like transition for the critical layer mode. Based on spatiotemporal and quadrant analyses, it is found that slip surfaces promote the prevalence of strong wall-toward motions (sweep-like events) near vortex cores close to the channel centre, inducing an early transition, while sustained ejection events are present in the region of the $Λ$-shaped vortex cores close to the critical layer, resulting in a delayed transition.
