Modelling of Rotating Turbulent Flows: Computer simulation of turbulent backward-facing step flow with system rotation

Abstract

An investigation of how different levels of turbulence modelling tackle the effects of system rotation has been performed. Ranging from simple one-equation models to large-eddy simulations, different approaches have been considered by means of a literature study and numerical calculations of turbulent flow over a backward-facing step subjected to spanwise rotation. The computed results were compared with results from direct numerical simulations.The literature study revealed that simple linear eddy-viscosity turbulence models are unable to predict any effects on the turbulence field due to system rotation. Eddy-viscosity models may be sensitised to rotation, but this has been done with a varying degree of success. The Reynolds stress equation models inherently respond well to system rotation, but a more costly eddy simulation will yield the most accurate result.Numerical calculations confirmed what was found in the literature. A linear eddy-viscosity model was unaffected by system rotation, while the sensitised model exhibited some effects on the mean flow field. The Reynolds stress model managed to predict all essential effects related to system rotation, although one separation bubble was oversized. This defect was attributed to a flaw in the modelling of the Reynolds stress redistribution process.