Comparison between RANS and LES Approaches to the Simulation of Natural Convection in a Differentially Heated Square Cavity

摘要

The capabilities of Fire Dynamics Simulator (FDS), a LES code for fire dynamics assessment, to correctly predict also a buoyancy driven flow in a small square cavity are discussed and compared with the results of a well established CFD solver (Ansys Fluent). In both cases, numerical predictions are compared with a detailed experimental benchmark available in the literature, where the flow field in a 0.75 m high, 0.75 m wide and 1.5 m deep cavity was extensively measured. Both the hot wall of the cavity and the cold one were isothermal (respectively at 50℃ and 10℃), giving a Rayleigh number of 1.58 × 10~9. A quite remarkable agreement between numerical and experimental data is obtained using Ansys Fluent, while new values of the coefficients for natural convection in FDS are hereby proposed, allowing a significant improvement of the capabilities of the code to reproduce the experimental heat transfer.