Structure-Based Turbulence Modeling in Complex Flows

Nearly each kind of fluid motion in our everyday surroundings is turbulent by nature, at least for fluids with high inertial forces and small viscous forces where the ratio of them is characterized by the well known Reynolds number. The appearance of turbulence ranges from the convection zone of our sun in the prediction of solar flares (space weather), the flow in our atmosphere (weather forecast) to the flow around ships, airplanes and buildings where the drag is of important interest for engineers. Engineers and physicists have therefore to map out the still unknown stochastic and three-dimensional nature of high Reynolds-number fluid motions. The Center for Turbulence Research at Stanford University, CA, deals with turbulent flow modeling. As the phenomena of turbulence are still unknown the use of simple eddy-viscosity turbulence closures for engineering applications is indispensable. These models form a compromise between numerical complexity and prediction capability. But they have great substantial deficits representing complex turbulent flows. A frequently cited example in the literature is the pressure-induced turbulent non-equilibrium, which is of high relevance in any industrial flow. A further deficit of eddy-viscosity models is the inability to capture three-dimensional effects, which are caused by the anisotropy of the turbulence. More complex models (e.g. Reynolds stress transport models) are in principle able to consider these effects, due to their complexity they have not been accepted for industrial applications. The aim of this project is now to combine the V2F eddy-viscosity turbulence model, which has become increasingly popular during the last years, with a newly developed structure-based turbulence model. As the structure-based turbulence closure is of very high complexity, numerical simplifications should be suggested to make them applicable also for complex flow configurations. The combined model should then be able to consider the previously mentioned turbulence phenomena and therefore to enhance engineering work dealing with turbulent flows.