AI 中文总结
本研究探究零压力梯度湍流边界层下方壁面压力统计的雷诺数演化，揭示其与大尺度运动的关联，明确内尺度与中/大尺度的不同雷诺数特性及对应的相干结构。
AI 中文摘要
本研究探究零压力梯度湍流边界层（TBL）下方壁面压力统计的雷诺数（Re_τ）演化规律，并将其对数变化与对数区中日益活跃的大尺度运动关联起来。研究发现，壁面压力偏度随Re_τ增大而变得更负，原因在于大尺度壁面压力波动（具有负偏度）的贡献增加，以及其与统计不变的内尺度波动（具有正偏度）的非线性相互作用增强。分析基于墨尔本隧道中5000 < Re_τ < 11300范围内壁面压力与流向速度的新的高分辨率同步测量、Re_τ约为10^6的大气边界层测量，以及Re_τ约为10^3的已发表模拟数据集。特别关注影响壁面压力统计的主要实验限制因素：空间分辨率、亥姆霍兹共振、设备噪声和统计收敛性。结果表明，即使经过常规修正，亥姆霍兹共振仍会污染内尺度壁面压力贡献，而可靠的偏度估计需要采集时长达到约10^5个涡 turnover 时间或更长。内尺度缩放的壁面压力谱在小尺度范围内具有雷诺数不变性，这与湍流通道流和管流不同；而在中尺度和大尺度范围内，其随Re_τ显著增长，与这些内部流动一致。线性和二次速度-壁面压力相干性将这些中尺度和大尺度贡献分别与两种动态不同的相干结构关联：自相似附着涡层级和湍流超结构。这些分析建立了惯性区与壁面压力方差及偏度随Re_τ对数变化之间的联系。
英文摘要
This study investigates the Reynolds-number (Re_τ) evolution of wall-pressure statistics beneath zero-pressure-gradient TBLs, and links their logarithmic variation to the increasingly energetic large-scale motions in the logarithmic region. The wall-pressure skewness is found to become more negative with increasing Re_τ, owing to increasing contributions from large-scale wall-pressure fluctuations (that are negatively skewed) and their nonlinear interaction with the statistically invariant inner-scale fluctuations (that are positively skewed). The analysis draws on new, well-resolved simultaneous measurements of wall pressure and streamwise velocity spanning 5000 < Re_τ< 11300 in the Melbourne tunnel, atmospheric surface-layer measurements at Re_τ= O(10^6) and a published simulation dataset at Re_τ= O(10^3). Particular attention is paid to the principal experimental limitations affecting wall-pressure statistics: spatial resolution, Helmholtz resonance, facility noise and statistical convergence. Helmholtz resonance is shown to contaminate inner-scale wall-pressure contributions even after conventional corrections, and reliable estimation of skewness is found to require acquisition durations of O(10^5) eddy-turnover times or longer. The inner-scaled wall pressure spectrum is Reynolds-number invariant over the small-scale regime, in contrast to turbulent channel and pipe flows, whereas at intermediate and large scales it grows substantially with Re_τ, consistent with these internal flows. Linear and quadratic velocity--wall-pressure coherence link these intermediate- and large-scale contributions to two dynamically distinct coherent structures: the self-similar attached-eddy hierarchy and turbulent superstructures, respectively. These analyses establish the connection between the inertial region and the log variation of wall-pressure variance and skewness with Re_τ
CommentsPreprint submitted for review to the Journal of Fluid Mechanics, with 28 pages and 11 figures
