论文标题
在湍流通道流动中壁压波动的波数频谱上
On the wavenumber-frequency spectra of the wall pressure fluctuations in turbulent channel flow
论文作者
论文摘要
进行湍流通道的直接数值模拟（DNS）流动到$re_τ\ the the的三维（由流向波数，跨度波数和频率）的三维（由壁压力波动）进行研究。为了开发来自波数光谱的波数频谱光谱的预测模型，研究了壁压波动的时间去相关机理。人们发现，使用类似的流向速度波动的类似随机扫描模型可以很好地预测壁压波动的波数波动的能量部分。为了完善研究，我们进一步将总壁压波动的光谱分解为快速和缓慢压力波动的自动光谱，以及它们之间的跨频谱。我们专注于评估许多预测模型中应用的假设，即横谱的大小明显很小。目前的DNS表明，对于所有正在测试的Reynolds数字，忽略跨频谱会导致亚对照区的最大误差高达4.7dB。我们的分析表明，忽略跨频谱的假设需要仔细应用于低马赫数的声学研究，其中壁压波动的亚对立组件对辐射的声学能力做出了重要贡献。
Direct numerical simulations (DNS) of turbulent channel flows up to $Re_τ \approx 1000$ are conducted to investigate the three-dimensional (consisting of streamwise wavenumber, spanwise wavenumber and frequency) spectrum of wall pressure fluctuations. To develop a predictive model of the wavenumber-frequency spectrum from the wavenumber spectrum, the time decorrelation mechanisms of wall pressure fluctuations are investigated. It is discovered that the energy-containing part of the wavenumber-frequency spectrum of wall pressure fluctuations can be well predicted using a similar random sweeping model for streamwise velocity fluctuations. To refine the investigation, we further decompose the spectrum of the total wall pressure fluctuations into the auto spectra of rapid and slow pressure fluctuations, and the cross spectrum between them. We focus on evaluating the assumption applied in many predictive models, that is, the magnitude of the cross spectrum is negligibly small. The present DNS shows that neglecting the cross spectrum causes a maximum error up to 4.7dB in the sub-convective region for all Reynolds numbers under test. Our analyses indicate that the assumption of neglecting the cross spectrum needs to be applied carefully in the investigations of acoustics at low Mach numbers, in which the sub-convective components of wall pressure fluctuations make important contributions to the radiated acoustic power.
