A New Version of the Dynamic Hybrid RANS-LES (DHRL) Model with Improved RANS-LES Blending

Abstract A new variant of the Dynamic Hybrid RANS-LES (DHRL) model is proposed in this paper. The DHRL modeling framework allows the combination of any RANS and any LES model using a physics-based RANS-to-LES blending based on the ratio of resolved to modeled turbulent stresses without any explicit grid metrics. This results in the DHRL model being relatively insensitive to changes in grid resolution alleviating some of the shortcomings of traditional HRL models such as Modeled-Stress Depletion. However, it has been observed that for flows where turbulent stresses are overpredicted by the RANS model, the DHRL model tends to incorrectly remain in a RANS-biased mode despite the presence of appreciable levels of LES fluctuations. To mitigate this issue, a new statistical variable is introduced and implemented into a modified blending function to facilitate model transition from RANS-to-LES more accurately. To validate the performance of the new DHRL model, numerical simulations are carried out using the density-based finite-volume solver, Loci-CHEM. The new DHRL model performance is evaluated against the baseline DHRL model and some traditional RANS and HRL models for canonical test cases such as fully developed channel flow, backward facing step, flow over a three-dimensional axisymmetric hill, and pulsating channel flow. A comprehensive analysis of results indicate that the new model successfully addresses some of the shortcomings of the baseline DHRL model and it is concluded that new DHRL model variant is a useful alternative to traditional HRL models.