Simulation and modelling of a skewed turbulent channel flow

A time-dependent three-dimensionally skewed flow is investigated using dire ct numerical simulations of the incompressible Navier-Stokes equations. The effect on the instantaneous and mean turbulent field is investigated. Inst antaneous flowfields reveal that the skewing has the effect of initially re ducing the strength and height of quasi-streamwise vortices of both signs o f rotation with respect to the skewing. A mechanism for this process is put forward. The mean flowfields show drops in turbulence quantities such as t urbulence kinetic energy. In addition to this, two-equation turbulence mode lling of the flow is carried out. This highlights a deficiency, in that the standard turbulence models are unable to capture the drop in turbulence in tensity due to the skewing. A modification based on the exact dissipation e quation is found to significantly improve the model behaviour for this flow .