Reynolds Number Effects in Wall-Bounded Turbulent Flows

Experimental measurements of the turbulent boundary layer flows with moderate and low Reynolds numbers in a wind tunnel are combined with measurements of the high Reynolds number wall turbulent flows in the atmospheric surface layer (ASL) at the Qingtu Lake Observation Array (QLOA) to reveal the Reynolds number effect on some basic turbulence statistics and the turbulent structures. The results show that the Karman constants of the ASL flows with \(Re_\tau \) \(\sim \) O(10 \(^6\) ) are larger than those of the low- and moderate-Reynolds-number boundary layer flows, and the Karman constants in sand-laden flows are greater than that in clean airflows. Taking the amplitude modulation coefficient between turbulent structures equal to 0 as the criterion to identify the midpoint of the logarithmic layer, the inner-scaled height of the midpoint and the lower bound of the logarithmic layer both increase linearly with the Reynolds number; The streamwise scales of the turbulent structures in the outer layer firstly increase and then tend to stabilize with the Reynolds number. The critical Reynolds number above which the scales of the very large scale motions (VLSMs) do not increase is about \(Re_\tau \) = 1200, and the critical Reynolds number at various heights has the same values. The energy contribution of the VLSMs in the outer layer increases with the Reynolds number in a log-linear way, and the maximum contributions of the VLSMs in ASL can exceed 65 \(\%\) .