Abstract
In this study, we use Large-Eddy Simulations (LESs) to provide a platform to investigate the separated and reattached turbulent flow over a heated blunt plate at ReH = 21 600. The surface Nusselt number and flow field data show good agreement with the published experiments. The turbulence anisotropy resolved by the LES shows that, through the recirculation region, the anisotropy develops toward an axisymmetric contraction state in the near-wall profile. In the redeveloping region, profiles show progression toward 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 modeling using an LES informed turbulence transport a priori analysis. The explicit algebraic Reynolds stress model showed improved agreement, capturing the elevated turbulent stresses in the recirculation region. Closures describing the turbulent heat flux are compared, and the Higher-Order Generalized GDH (HOGGDH) closure is discovered to show good agreement with those resolved by the LES, capturing the correct ratio of the streamwise to normal turbulent heat flux across the redeveloping boundary layer. An explicit algebraic scalar flux model 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.
Highlights
The study of turbulent flow and heat transfer in separated and reattached flow regimes is of practical interest to the engineering community
Large-Eddy Simulations (LES) of the geometrically simple heated blunt plate showed a variety of complex turbulent behaviours for the moderate Reynolds number of 21, 600 studied
This paper showed that LES using the Wall-Adaptive Local Eddy-viscosity (WALE) sub-grid scale model provided accurate predictions of the surface heat transfer and turbulent flow behaviour
Summary
The study of turbulent flow and heat transfer in separated and reattached flow regimes is of practical interest to the engineering community. Heat exchangers and turbine blades are just a few examples of where these flows are present and to understand and predict their heat transfer is vital for product lifetimes and performance. High Reynolds numbers, common within these applications, promote instabilities within the shear layer and the onset of turbulence is close to the separation point. The complexities of the flow present challenges to commonly used, efficient and low-cost two-equation Reynolds-Averaged Navier Stokes (RANS) approaches where a desire for improved accuracy is sought for component design. Understanding the RANS closures within these flows allows for improved engineering judgement and may provide a foundation for further closure development
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