Effects of Low Reynolds Number on the Outer Layer Structure in a Smooth Wall Turbulent Boundary Layer. Re-examination of Statistical Quantities.

Abstract

Re-examination of the low-Reynolds-number effect on the outer layer structure has been made in a zero pressure gradient, smooth wall turbulent boundary layer where the two-dimensionality of a flow field was corroborated using the momentum integral equation. The measurements associated with the higher-order moments and the conditional averages were made over a momentum thickness Reynolds number range 840&InE;Rθ&InE;6120. The magnitude of the triple products normalized with friction velocity and relative typical eddy scale Cx/δ are affected with a achievement level of the two-dimensionality of a flow field. For Rθ<2130, the absolute values of the triple products and the turbulent diffusion terms normalized with outer variables increase with Rθ. Intermittency factor is approximately independent of Rθ when Rθ is greater than 4410. Therefore, average turbulent and non-turbulent zone lengths are constant independent of Rθ.