Canadian Journal of Chemical Engineering, Vol.98, No.5, 1225-1236, 2020
Numerical investigation of turbulent shear flows using production-limited delayed detached-eddy simulation
In chemical engineering, turbulent shear flows are often encountered. The grid induced separation (GIS) and the slow RANS-LES transition issues should be alleviated when the delayed detached-eddy simulation (DDES) is used to simulate turbulent shear flows. This paper studies the performance of the production-limited DDES (PL-DDES) model in improving the GIS and the slow RANS-LES transition issues. Since the simplified IDDES (S-IDDES) model is proposed to improve the GIS issue, the S-IDDES model is chosen as the model for comparison. The simulation results show that the PL-DDES model with constant C-d1 = 14 alleviates the GIS issue better than the S-IDDES model and the PL-DDES model with C-d1 = 8. The results of the free shear layer show that the PL-DDES model can switch RANS to LES more rapidly and unlock the Kelvin-Helmholtz instability more effectively than the S-DDES model. For the backward-facing step flow, the S-IDDES model performs poorly when unlocking the Kelvin-Helmholtz instability in the separation zone. On the other hand, the PL-DDES model has a rapid RANS-LES transition after the step and produces a significant transport of momentum in the shear layer, leading to reasonable separation distance and flow structures.