Turbulent closure analysis in heated separated and reattached flow using eddy-resolving data

Abstract

In this study, we use Large-Eddy Simulations (LES) to provide a platform to investigate the separated and reattached turbulent flow over a heated blunt plate at Re H = 21600. Surface Nusselt number and flow field data show good agreement with published experiments. The turbulence anisotropy resolved by the LES shows that through the recirculation region the anisotropy develops towards an axisymmetric contraction state in the near-wall profile. In the redeveloping region, profiles show progression towards the plane-strain state. Turbulent closures, providing simple models of the unknown turbulent correlations that arise from the Reynolds-averaging of the Navier-Stokes equations, are routinely applied to complex flows, often with little known about their suitability. The eddy-resolved flow field is used to describe deficiencies in Reynolds-Averaged Navier-Stokes (RANS) modelling using an LES informed Turbulence Transport (LiTT) a priori analysis. The Explicit Algebraic Reynolds Stress Model (EARSM) showed improved agreement, capturing the elevated turbulent stresses in the recirculation region. Closures describing the turbulent heat flux are compared and the Higher-Order Generalised GDH (HOGGDH) closure is discovered to show good agreement with those resolved by the LES, capturing the correct ratio of streamwise to normal turbulent heat flux across the redeveloping boundary layer. An Explicit Algebraic Scalar Flux Model (EASFM) is examined and shows good predictions of the turbulent heat flux angle but underpredicts the magnitude across the recirculation region. An optimal coefficient for the HOGGDH is described to reproduce the turbulent heat flux magnitude from the LES, showing a range of optimal values across the flow.

Impact of inflow turbulence on large‐eddy simulation of film cooling flows

“…Sub-grid scale contributions to thermal diffusivity are achieved with a sub-grid scale Prandtl number of 0.4, providing successful results in Schindler et al [16] and Ellis and Xia [17] . Contributions to the energy equations are shown by Eq.…”