Statistical Structure at the Wall of the High Reynolds Number Turbulent Boundary Layer

Abstract

The paper reports on the application of the Time-dependent Reynolds-Averaged Navier-Stokes (T-RANS) approach to analysing the effects of magnetic force and bottom-wall configuration on the reorganisation of a large coherent structure and its role in the transport processes in Rayleigh-Benard convection. The large-scale deterministic motion is fully resolved in time and space, whereas the unresolved stochastic motion is modelled by a `subscale' model for which the conventional algebraic stress/flux expressions were used, closed with the low-Re number - - three-equation model. The applied method reproduces long-term averaged mean flow properties, turbulence second moments, and all major features of the coherent roll/cell structure in classic Rayleigh-Benard convection in excellent agreement with the available DNS and experimental results. Application of the T-RANS approach to Rayleigh-Benard convection with wavy bottom walls and a superimposed magnetic field yielded the expected effects on the reorganisation of the eddy structure and consequent modifications of the mean and turbulence parameters and wall heat transfer.