Coherent Structures in Turbulent Boundary Layer with Adverse Pressure Gradients
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摘要: 利用流动稳定性理论中一般共振三波的概念对4种定常逆压梯度以及两种变逆压梯度湍流边界层的相干结构进行研究.其中2种变逆压梯度分别为压力梯度由小变大和由大变小,变化的终了具有相同的压力梯度.通过计算得出逆压梯度能够激励相干结构的生成和发展,而且逆压梯度越大作用越强.在变压力梯度流动中,压力梯度由大变小的情况对相干结构的激励最强.此外,逆压梯度使相干结构的流向尺度变小,而展向间距基本在100个粘性长度左右,这些变化趋势与实验以及直接数值模拟结果一致.Abstract: By using the idea of resonant triad of the theory of hydrodynamic stability, the coherent structures in a turbulent boundary layer were investigated as a function of steady-adverse-pressure-gradient(SAPG) and changing-adverse-pressure-gradient(CAPG) flow cases. It was found that the adverse pressure gradient enhanced the growth rate of the resonant triads, enlarged the parameter range for the growing cases, and reduced the streamwise dimension, while the spanwise spacing of the streaky structures in all four cases remained approximately the same. And the greater the adverse pressure gradient, the stronger the above effects. For CAPG flows, the case with reducing pressure gradient produced the strongest effect on the coherent structures, though the same pressure gradient was remained in the end of evolution.
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Key words:
- turbulent boundary layer /
- pressure gradients /
- waves
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