2019/01/07 by Paolo Orlandi, Orlandi, Paolo · 1 citation
Engineering · Environmental Science · #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Fluid Dynamics and Turbulent Flows #Fluid Dynamics and Vibration Analysis #Heat Transfer Mechanisms #Wind and Air Flow Studies
paper · pdf · doi:10.48550/arxiv.1901.01755
openalex publication_date 2019/01/07 · openalex created_date 2022/10/02 · openalex updated_date 2026/07/28
Data available in literature from direct numerical simulations of\ntwo-dimensional turbulent channels by Lee & Moser (2015), Bernardini et al.\n(2014), Yamamoto and Tsuji (2018) and Orlandi et al. (2015) in a large range of\nReynolds number have been used to find that shear parameter the ratio between\nthe eddy turnover time and the time scale of the mean deformation (1/S), scales\nvery well with the Reynolds number in the near-wall region. The good scaling is\ndue to the eddy turnover time, although the turbulent kinetic energy and the\nrate of isotropic dissipation show a Reynolds dependence near the wall. the\nshear parameter is linked to the flow structures, as well as the second\ninvariant, and also this quantity presents a good scaling. It has been found\nthat the maximum of turbulent kinetic energy production occurs in the layer\nwith the second invariant approximately zero, that is where the unstable\nsheet-like structures roll-up to become rods. The decomposition of production\nin the contribution of elongational and compressive strain demonstrates that\nthe two contribution present a good scaling. The perfect scaling however holds\nwhen the near-wall and the outer structures are separated. The same statistics\nhave been evaluated by direct simulations of turbulent channels with different\ntype of corrugations on both walls. The flow physics in the layer near the\nplane of the crests is strongly linked to the shape of the surface and it has\nbeen demonstrated that the normal to the wall velocity fluctuations are\nresponsible for the modification of the flow structures, for the increase of\nthe resistance and of the turbulent kinetic energy production. These\nsimulations at intermediate Reynolds number indicated that in the outer region\nthe Townsend similarity hypothesis holds.\n