A dynamic detached-eddy simulation model for turbulent heat transfer: Impinging jet

In this study, the simulation of wall heat transfer in impinging jets is comprehensively investigated. A new turbulent thermal diffusivity formulation conjugated with a dynamic delayed detached-eddy simulation (DDES) model is proposed, based on a strict assessment and a detailed analysis of the near-wall performance of constant-coefficient DDES/IDDES and LES models. The simulations are conducted at a nozzle-to-wall distance of H/D = 2 and 4 with a Reynolds number of Re = 40,000. The measurement data obtained by temperature-sensitive paint (TSP) and particle image velocimetry (PIV) are used for validation. Impinging jets at Re = 23,000 and 70,000, in accordance with the literature, are used for further validation. The definition of the shielding function in a previous version is modified by using an alternative formulation, which is averaged only in a thin layer near the wall and is not sensitive to the computational domain size. A alpha(t) model is proposed for impingement heat transfer, using a constant Pr-t model in the impingement region and a shear rate-based alpha(t) formulation in the wall-jet region. The dynamic DDES model conjugated with the new alpha(t) model accurately predicts the wall Nusselt number distributions in each impinging jet. The LES and dynamic DDES conjugated with the existing Pr-t model underestimate the heat transfer coefficient in the wall-jet region, due to the insufficient eddy resolving capacity that cannot compensate for the turbulent eddy viscosity attenuation in the heat transfer model. The constant-coefficient DDES and improved DDES (IDDES) produce excessive turbulent eddy viscosity in the flow, leading to the high model-dependence of the results. (C) 2018 Elsevier Ltd. All rights reserved.