Large-Eddy Simulation of Conductive Flows at Low Magnetic Reynolds Number.

摘要

In large-eddy simulations (LES), only the large-scale structures of the flow are simulated directly while the small-scale structures are taken into account through a model, referred to as the subgrid-scale (SGS) model. This results in significant reduction in computational requirements. The trade-off comes in the extra modelling effort that has to be produced in order to adequately take into account the discarded small scales structures. In the computational fluid mechanics community, the most widely used SGS model is the Smagorinsky eddy viscosity model (Smagorinsky 1963). This model has gained an even bigger practical interest following the work of Germano et al. (1991) in which the dynamic procedure was introduced, The dynamic procedure enables optimization 'on the fly' of the arbitrary scaling factor that is inherently present in the original Smagorinsky model (more details below) and thus allows the model to automatically adapt to the flow being studied. In this paper we study the LES method with dynamic procedure in the context of conductive flows subject to an applied external magnetic field at low magnetic Reynolds number R(sub m). These kind of flows are encountered in many industrial applications. For example, in the steel industry, applied magnetic fields can be used to damp turbulence in the casting process. In nuclear fusion devices (Tokamaks), liquid- lithium flows are used as coolant blankets and interact with the surrounding magnetic field that drives and confines the fusion plasma. Also, in experimental facilities investigating the dynamo effect, the flow consists of liquid-sodium for which the Prandtl number and, as a consequence, the magnetic Reynolds number is low.