Direct and large-eddy simulation of turbulent fluid flow using the lattice-Boltzmann scheme

This paper reports on direct and large-eddy simulations (LES) of turbulent flows using the lattice-Boltzmann scheme for the discretization of the Navier-Stokes equations. It is divided into two parts. The first part deals with direct simulation of fully developed turbulent channel flow with heat transfer in order to check the performance of our solver. It is shown that the present numerical results agree well with the numerical results reported by Kim et al. (1987). The second part deals with large-eddy simulation (LES) of the turbulent flow in a baffled stirred tank reactor. This kind of equipment is frequently used in the (petro)chemical industry for mixing applications and is, therefore, of direct practical relevance. Large-eddy simulation is a powerful tool to study such flows, as it accounts in a natural way for the unsteady and quasi-periodic behavior of these flows. The results of our first attempt to simulate this flow by means of modeling the impact of the mechanical impeller on the flow field via a varying force field in space and time, reveal a fair agreement with available experimental data. In accordance with measurements, it is shown that the thickness of the impeller blades plays an important role for the motion of the fluid in the vicinity of the impeller. In conclusion, the present application of LES to this engineering flow problem clearly shows the potential of LES as a tool to investigate turbulent flows in industrial applications of practical importance.