The negatively buoyant wall-jet: LES results

摘要

The results of a Large-Eddy Simulations (LES) of a downward hot wall-jet injected against a cold upward channel flow are presented. Based on the experiment of He et al. (2002) [Int. J. Heat Fluid Flow 23 (2002) 487], this flow was suggested as an "application challenge" by the power generation industrial sector to the Qnet-CFD EU network. Indeed, numerical predictions vary significantly with the type of RANS model used, with only the most advanced models yielding reasonable agreement with the experiment as presented in a companion paper by Craft et al. [Int. J. Heat Fluid Flow 25 (2004) 809]. The present LES was attempted to hopefully confirm and complete the experimental data, which in some areas can be sparse. As resources limited the LES to 1/2 million nodes, an optimal LES mesh was defined from RANS derived scales. Then to reduce uncertainties, two independent codes are used to perform the simulations: the commercial code Star-CD and an industrial one, Code_Saturne. The statistical quantities compared with the experimental data show that both codes are able to return fairly satisfactory results for the isothermal and moderately buoyant cases. For the third and strongly buoyant case comparison was only qualitative.