DNS of a Turbulent Stirred Vessel with Baffles and a Rushton Turbine

We report on a Direct Numerical Simulation (DNS) for a stirred tank provided with four baffles and a six-bladed Rushton turbine, operated in the turbulent regime (Re = 7,300). The incompressible and isothermal Navier-Stokes equations are discretized using a Lattice Boltzmann method and the no-slip boundary condition is enforced using an adaptive force field technique. To resolve all turbulent scales during 20 turbine revolutions, a total of 4 billion grid-points and 10e5 time-steps are computed. The job was performed during one month on 128 CPU cores.

In the talk, we focus on a comparison between LES and DNS. We point out where LES fails and suggest ways for improving the sub-grid modeling. Also we show visualizations of the vortical structures in the wake of a single turbine blade.