The structure of wall-pressure fluctuations in turbulent boundary layers with adverse pressure gradient and separation
The structure of wall-pressure fluctuations in turbulent boundary layers with adverse pressure gradient and separation
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DOI：
10.1017/s0022112098003218
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发表时间：
1998-12
影响因子：
3.7
通讯作者：
Y. Na;P. Moin
中科院分区：
文献类型：
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作者：
Y. Na;P. Moin
通过对直接数值模拟得到的壁压脉动的时空关联和频谱分析，揭示了压力梯度和分离度对壁压脉动特性的影响。在受逆压梯度作用的附面边界层中，壁面压力脉动的两点恒定空间相关的等高线在展向上更加拉长。壁面压力波动的对流速度随时间和空间分离的函数被逆压梯度降低。在分离的湍流边界层中，分离气泡内部的壁压脉动减小，再附着区下游的壁压脉动增强，这是雷诺应力最大的地方。在分离气泡内部，局部最大雷诺切应力归一化的壁压脉动频谱与自由流动压归一化的壁压脉动频谱具有较好的相关性，表明局部雷诺切应力对壁压谱有更直接的影响。壁压波动的两点相关等高线在分离气泡内沿跨向高度拉长，表明存在较大的二维滚柱型结构。由壁面压力脉动的时空相关性确定的对流速度在分离区内低至0.33U0(U0为最大入口速度)，并在再附着后向下游增加。
Space–time correlations and frequency spectra of wall-pressure fluctuations, obtained from direct numerical simulation, are examined to reveal the effects of pressure gradient and separation on the characteristics of wall-pressure fluctuations. In the attached boundary layer subjected to adverse pressure gradient, contours of constant two-point spatial correlation of wall-pressure fluctuations are more elongated in the spanwise direction. Convection velocities of wall-pressure fluctuations as a function of spatial and temporal separations are reduced by the adverse pressure gradient. In the separated turbulent boundary layer, wall-pressure fluctuations are reduced inside the separation bubble, and enhanced downstream of the reattachment region where maximum Reynolds stresses occur. Inside the separation bubble, the frequency spectra of wall-pressure fluctuations normalized by the local maximum Reynolds shear stress correlate well compared to those normalized by free-stream dynamic pressure, indicating that local Reynolds shear stress has more direct influence on the wall-pressure spectra. Contour plots of two-point correlation of wall-pressure fluctuations are highly elongated in the spanwise direction inside the separation bubble, implying the presence of large two-dimensional roller-type structures. The convection velocity determined from the space–time correlation of wall-pressure fluctuations is as low as 0.33U0 (U0 is the maximum inlet velocity) in the separated zone, and increases downstream of reattachment.