Turbulence intensity in wall-bounded and wall-free flows

摘要: Turbulence intensity variations in the outer region of turbulent shear flows are considered, context diagnostic plot first introduced by Alfredsson et al. (Phys. Fluids, vol. 23, 2011, 041702) and for both (smooth rough) wall-bounded classical free flows. With U defined as mean velocity within flow, Ue a suitable reference u? root square fluctuating velocity, it is demonstrated that, wall flows, attached eddy hypothesis yields closely linear (u?/U versus U/Ue) over certain Reynolds number range, explaining why relation seems to work well boundary layers channels despite its lack any physical basis (Castro al., J. Fluid Mech., 727, 2013, pp. 119–131). It shown that mixing layers, jets wakes also exhibit u?/U U/Ue much (starting roughly from where turbulence production maximum), with slopes these determined total strain rate, characterised Townsend’s flow constant Rs. The thus has wider range applicability than might have been anticipated.