A finite element LES for high-Re flow in a short-elbow pipe with undisturbed inlet velocity

The paper is concerned with a large-eddy simulation (LES) for a high-Reynolds-number flow in a short-elbow pipe, which can potentially be employed in the primary piping system of the Japan Sodium-cooled Fast Reactor (JSFR). The basic performance of the LES is studied for an elbow pipe flow without turbulence at inlet boundary at Re = 1.2 × 106 by comparison with a flow observed in a 1/3-scale water experiment, where the flow disturbance at the pipe inlet is small. In setting up the computational conditions, special care was taken to ensure that the mesh subdivision was suitable for the simulation of the pipe flow through a theoretical consideration. We discuss the effects of the turbulence model (Smagorinsky model, WALE model) and the inlet velocity profile on the results. The mechanism of the pressure fluctuation and the origin of the fluid force are also discussed with the aid of spectral analysis and the visualization of essential hydraulic quantities.

Research highlights► We simulate a high-Reynolds-number flow in a short-elbow pipe with LES. ► We examine the effects of SGS model and inlet velocity profile without fluctuation. ► We find the thicker the boundary layer at inlet, the weaker the flow separation. ► We find the WALE model induce unphysical SGS viscosity for rigidly rotating flow. ► Unsteady force can be explained by Dean vortices destabilized by flow separation.