In the present study, direct numerical simulation (DNS) is carried out in a minimal channel at $Re_{\unicode[STIX]{x1D70F}}=2000$ to sustain healthy turbulence below $y^{+}=100$. Turbulence intensities are compared with those of the motions at the same scales as the minimal channel in the full-sized channel at $Re_{\unicode[STIX]{x1D70F}}=2003$ (Hoyas & Jiménez, Phys. Fluids, vol. 20 (10), 2008, article 101511). They show good agreement in $y^{+}<100$. The universal signals for the three velocity components similar to that in the predictive model of Marusic et al. (Science, vol. 329 (5988), 2010, pp. 193–196) are extracted from the DNS data of the full-sized channel. They correspond well to the near-wall velocity fluctuations in the minimal flow unit (MFU). The predictive models for the three components of near-wall velocity fluctuations are proposed based on the MFU data. The predicted turbulence intensities as well as the joint probability density functions of velocity fluctuations agree well with the DNS results of the full-sized channel turbulence.
Extension of QSQH theory of scale interaction in near-wall turbulence to all velocity components
