Direct Numerical Simulation of Turbulent Velocity, Pressure, and Temperature Fields in Channel Flows

摘要

For the simulation of nonsteady, three-dimensional, turbulent flow- and temperature-fields in channel flows of fluids with constant properties a method is presented which is based on a finite difference scheme of the complete conservation equations for mass, momentum, and enthalpy. The fluxes of momentum and heat within the grid cells are described by subgrid scale models. The subgrid scale model for momentum introduced here is for the first time applicable to small Reynolds numbers, rather coarse grids, and channels with space-dependent roughness distributions. The new developed subgrid scale model for temperature also takes the influence of the molecular Prandtl number into consideration. For Prandtl numbers of about one, the theoretical model confirms the empirically derived values for the turbulent subgrid scale Prandtl number, which are currently used by other authors. For very small molecular Prandtl numbers of liquid metals, the model shows that the total resolution of all relevant temperature fluctuations can be achieved on the basis of presently realizable grids. The method is realized in the computer code TURBIT-2. It can be used for the simulation of laminar flows in plane channels and annuli as well as for turbulent flows with Reynolds numbers larger than about 10 exp 4 . The numerical results for the flow field show only a small influence of the model parameters. For smooth, rough, and partly roughened channels with secondary flows the agreement with experimental results is fairly good even when rather coarse grids are used. The temperature fields simulated are very insensitive to the parameters of the model. The numerical results are in good agreement with consistent, reliable experimental results. (ERA citation 04:049942)