Velocity and scalar spectra in a turbulent channel flow are examined using DNS databases with passive scalar transport (h⁺=180, 395, 640 and 1020 at Pr=0.71). Particular attention has been given to both kx and kz spectra in the outer region. In contrast to previous findings in the literature, the -5/3 power law does not hold for either velocity or scalar kx spectra over the present h⁺ range. For the kz spectrum, the scaling range slope of the θ spectrum is, however, closer to -5/3 than that of the u spectrum. This behaviour is most likely associated with large-scale spanwise mixing of θ.
6th International Symposium on Turbulence, Heat and Mass Transfer (THMT '09). Turbulence, Heat and Mass Transfer 6: Proceedings of the Sixth International Symposium on Turbulence, Heat and Mass Transfer (Rome, Italy 14-18 September, 2009) p. 119-122