Towards Modelling the Downstream Development of a Turbulent Boundary Layer Following a Rough-to-Smooth Step Change in Surface Condition
Towards Modelling the Downstream Development of a Turbulent Boundary Layer Following a Rough-to-Smooth Step Change in Surface Condition
复制标题
模拟表面条件从粗糙到平滑的阶跃变化后湍流边界层的下游发展
DOI：
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发表时间：
2019
期刊：
影响因子：
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通讯作者：
P. Fatt
中科院分区：
文献类型：
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作者：
G. Falk;P. Fatt
- 在这项研究中，我们研究了摩擦雷诺数Re（cid：28）和粗糙度雷诺数k + s在湍流边界层上的效果后，表面条件沿着湍流方向的粗糙到光滑的阶跃变化。为了研究Re（cid：28）的效应，在k + s = 160时进行了一组风洞实验，而Re（cid：28）从7100变化到21000。类似地，为了检查对k + s的依赖性，在Re（cid：28）= 14000处进行一组测量，其中k + s范围从110到230。热线剖面是在阶梯变化下游边界层厚度为120的几何间隔网格上获得的，局部壁面剪应力是直接使用油膜干涉测量法测量的。利用这些数据，我们提出了一个新的恢复平均速度分布模型，该模型解释了众所周知的内层非平衡行为。然后，使用积分流向动量方程，在阶跃变化的下游演化出该平均速度分布，以实现平均湍流恢复的完整预测。
— In this study we examine the effect of both the friction Reynolds number Re (cid:28) and the roughness Reynolds number k + s on a turbulent boundary layer following a rough-to-smooth step change in surface condition along the flow direction. To investigate the effect of Re (cid:28) , a set of wind-tunnel experiments is conducted at k + s = 160 while Re (cid:28) is varied from 7100 to 21000. Sim-ilarly, to examine the dependence on k + s , a set of measurements is conducted at Re (cid:28) = 14000 with k + s ranging from 110 to 230. Hot-wire profiles are obtained on a logarithmically spaced grid up to 120 boundary-layer thicknesses downstream of the step change, and the local wall-shear stress is measured directly using oil-film interferometry. Using these data, we propose a new model of the recovering mean velocity profile which accounts for the well-known non-equilibrium behaviour of the internal layer. This mean velocity distribution is then evolved downstream of the step change using the integrated streamwise momentum equation to achieve a full prediction of the mean flow recovery.