The phase of the bispectrum of a turbulent velocity signal is presented as a unified tool to relate the geometry and energetics of interactions between large- and small-scale motions in wall-bounded turbulence. The normalized bispectrum naturally describes nonlinear triadic interactions and thus is ideally suited for measuring the magnitude of coupling between the different scales of turbulence without the use of filtering procedures. In this study, the corresponding biphase is shown to represent the delay between large and small scales imposed by convective interactions and simultaneously to describe the direction of the turbulent streamwise energy cascade. The bispectrum and biphase are measured from a direct numerical simulation of a high-Reynolds-number channel flow and used to illustrate the relationship between the relative geometry of the interacting scales, the interaction delay, and the cascade of energy between them, offering an integrated perspective on scale interactions in turbulence through a single statistic.

中文翻译：

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双相诊断壁面湍流中尺度相互作用的诊断

湍流速度信号双谱的相位作为统一工具呈现，用于关联壁边界湍流中大尺度运动和小尺度运动之间的相互作用的几何学和能量学。归一化的双谱自然地描述了非线性三重相互作用，因此非常适合在不使用滤波程序的情况下测量不同湍流尺度之间的耦合幅度。在这项研究中，相应的双相被表示代表对流相互作用在大尺度和小尺度之间的延迟，同时描述了湍流能量级联的方向。