Abstract

We investigate the lifecycle of Reynolds stress in the turbulent channel flows at a high Reynolds number. Each term in the Reynolds stress transport equation is spectrally decomposed to uncover the contribution of mean and turbulence at different length scales and wall-normal distances. The streamwise-elongated large-scale structures have important contributions to the production of Reynolds stress in the outer region and transport of Reynolds stress to the near-wall region. In general, inter-scale transfer mechanisms enhance the isotropy in scales and its direction is from large-scale to small-scale except for the near-wall region where inverse energy cascade is observed. The inter-component transfer mechanism exhibits the multi-step behavior when it transfers from streamwise fluctuations to wall-normal and spanwise fluctuations. Finally, dissipation spectra become isotropic, and their scale grows with y^{1/4}.