Figure 13

Streamwise velocity: observed phase speed C(k) of the field near the wall and the channel’s centre (black lines) and theoretical CH dispersion of Eq. (2) (red lines) are shown in the top panels. The respective spectra \(S(k)/S_{max}\) normalized by their peak amplitude \(S_{max}\) are shown in the bottom panels. Estimated parameters \(u_0,C_0,\alpha , \beta\) of the CH dispersion are also shown. Wall: \(u_0=0.001\), \(C_0=0.042\), \(\alpha =0.95\), \(\beta =1.9 \cdot 10^{-6}\). Center: \(u_0=0.001\), \(C_0=0.064\), \(\alpha =4\), \(\beta =2.9 \cdot 10^{-5}\).