Abstract

Analytical tools, like CFD models, need to accurately predict the near-wall flow behavior on coarse meshes, where the boundary layer is not resolved. This is important for wall heat transfer analysis and gas turbine engines durability assessment. Such coarse-mesh models are practical from an engineering standpoint, when trade studies need to be run for design evaluation. Hybrid turbulence models, like the Stress-Blended Eddy Simulation (SBES), use Large Eddy Simulation (LES) closure in the bulk separated turbulent flow, where mesh density is high, and Reynolds-Averaged Navier-Stokes (RANS) closure near the wall in the under-resolved boundary layer. In the current work, the impact of near-wall RANS closure modeling, inflow turbulence, and near-wall mesh resolution on wall heat transfer analysis is examined in the context of hybrid SBES. The predicted wall heat transfer coefficient is compared and assessed with experimental data for a canonical heated-wall expansion pipe flow. The SST-k-ω model showed more physical and consistent behavior near the wall compared to the realizable k-ε model with enhanced wall treatment. Guidelines for SBES simulation practices for coarse mesh setups are provided. The study is useful for practical CFD simulations for gas turbine combustors, where higher mesh resolution is not affordable near the wall and wall functions are the only resolution.