Mechanisms of surface pressure distribution within a laminar separation bubble at different Reynolds numbers
Mechanisms of surface pressure distribution within a laminar separation bubble at different Reynolds numbers
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DOI：
10.1063/1.4913500
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发表时间：
2015-02
影响因子：
4.6
通讯作者：
Donghwi Lee;S. Kawai;T. Nonomura;M. Anyoji;H. Aono;A. Oyama;K. Asai;K. Fujii
中科院分区：
文献类型：
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作者：
Donghwi Lee;S. Kawai;T. Nonomura;M. Anyoji;H. Aono;A. Oyama;K. Asai;K. Fujii
采用基于弦长雷诺数5.0 × 103、6.1 × 103、1.1 × 104和2.0 × 104的大涡模拟方法，研究了层流分离泡（LSB）内部压力分布和表面摩擦的机制。LSB内部的特性随雷诺数的变化而变化；一个雷诺数为5.0 × 103和6.1 × 103的稳定层流分离泡（LSB_S）和一个雷诺数为1.1 × 104和2.0 × 104的稳定波动层流分离泡（LSB_SF）。通过增加雷诺数，观察到压力和摩擦分布的不同特征，使得LSB_S内的压力恢复逐渐单调，而LSB_SF内的压力分布呈平台分布，随后进入快速恢复区。通过推导雷诺平均压力梯度方程，讨论了不同雷诺数下压力分布特征不同的原因。证实了近地表的粘性应力分布对不同压力分布的形成起着重要的决定作用。根据雷诺数的不同，表面附近的粘性应力分布受到分离的层流剪切层的发展或雷诺剪切应力的影响。此外，我们表明，同样的分析可以应用到流动周围的NACA0012翼型。
Mechanisms behind the pressure distribution and skin friction within a laminar separation bubble (LSB) are investigated by large-eddy simulations around a 5% thickness blunt flat plate at the chord length based Reynolds number 5.0 × 103, 6.1 × 103, 1.1 × 104, and 2.0 × 104. The characteristics inside the LSB change with the Reynolds number; a steady laminar separation bubble (LSB_S) at the Reynolds number 5.0 × 103 and 6.1 × 103, and a steady-fluctuating laminar separation bubble (LSB_SF) at the Reynolds number 1.1 × 104, and 2.0 × 104. Different characteristics of pressure and skin friction distributions are observed by increasing the Reynolds number, such that a gradual monotonous pressure recovery in the LSB_S and a plateau pressure distribution followed by a rapid pressure recovery region in the LSB_SF. The reasons behind the different characteristics of pressure distributions at different Reynolds numbers are discussed by deriving the Reynolds averaged pressure gradient equation. It is confirmed that the viscous stress distributions near the surface play an important role in determining the formation of different pressure distributions. Depending on the Reynolds numbers, the viscous stress distributions near the surface are affected by the development of a separated laminar shear layer or the Reynolds shear stress. In addition, we show that the same analyses can be applied to the flows around a NACA0012 airfoil.