Hybrid methods are emerging as an excellent tool to numerically simulate complex turbulent flows at high Reynolds numbers. As such, they have been repeatedly shown to overcome some of the computational difficulties typical of DNS and LES, while still providing robust results. Several approaches are known in literature, some of them based on spectral properties [1][], others combining scale-dependent methods [3][4].
Here, we introduce a generalized seamless RANS-LES hybrid model to efficiently simulate the dynamics of buoyancy-driven flows. Unlike previous attempts to combine RANS and LES, our approach does not rely on a clear spatial separation, that is wall-region vs. bulk volume, but it instead switches in between the two by means of fluctuation-dependent criterion. This is particularly useful when, as in the case of buoyancy driven-flows, turbulence production occurse in the whole volume and not just near the wall. We apply this model to Rayleigh-Benard convection at high Rayleigh number and compare our simulations to previous LES results from literature, showing a good agreement that paves the way to future investigations.
[1] Chaouat B., and Schiestel R., Theor. Comput. Fluid Dyn. 21, 201-229 (2007)
[2] Girimaji S.S., Srinivasan R., Jeong E., Proc. ASME FEDSM’03, ASME paper n 45336, 1-9 (2003)
[3] Spalart PR., Annu. Rev. Fluid Mech. 41, 181-202 (2009)
[4] L Temmerman, M Hadžiabdić, MA Leschziner, K Hanjalić, Int. J. of Heat and Fluid Flow 26 (2), 173-190 (2005)
LSM / CFD