An attempt to combine large eddy simulation with the k-epsilon model in a channel-flow calculation

Large eddy simulation (LES) is combined with the Reynolds-averaged Navier-S tokes (RANS) equation in a turbulent channel-flow calculation. A one-equati on subgrid-scale model is solved in a three-dimensional grid in the near-wa ll region whereas the standard k-epsilon model is solved in a one-dimension al grid in the outer region away from the wall. The two grid systems are ov erlapped to connect the two models smoothly. A turbulent channel flow is ca lculated at Reynolds numbers higher than typical LES and several statistica l quantities are examined. The mean velocity profile is in good agreement w ith the logarithmic law. The profile of the turbulent kinetic energy in the near-wall region is smoothly connected with that of the turbulent energy f or the k-epsilon model in the outer region. Turbulence statistics show that the solution in the near-wall region is as accurate as a usual LES. The pr esent approach is different from wall modeling in LES that uses a RANS mode l near the wall. The former is not as efficient as the latter for calculati ng high-Reynolds-number flows. Nevertheless, the present method of combinin g the two models is expected to pave the way for constructing a unified tur bulence model that is useful for many purposes including wall modeling.