Turbulent separated inert and reactive flows over a triangular bluff body

Application Challenge AC2-12 © copyright ERCOFTAC 2019

Best Practice Advice

Key Fluid Physics

The Reynolds numbers based on the side of the bluff-body and bulk velocity are estimated as Re=28,000 – 47,000, and the flow can be considered to be in the sub-critical regime for the inert simulations. The combustion is characterized by the lean, premixed propane-air mixture of equivalence ratio ?=0.58-0.65 (“thin reaction zone” regime). The key features of the flow mechanics are the laminar boundary layer, separated shear layer, wake and the flow instabilities that provide complex, nonlinear interactions between them. The wake is dominated by two types of instabilities: the convective instabilities or asymmetric vortex shedding the (Bénard/von Kármán instability) and Kelvin–Helmholtz instability (sometimes called absolute) of the separated shear layer. For the reactive cases, the flame introduces additional phenomena trough effects of exothermicity and flow dilatation on the flow field, which leads to the large differences between the non-reacting and the reacting wakes.

Contributed by: D.A. Lysenko and M. Donskov — 3DMSimtek AS, Sandnes, Norway