Numerical investigation of radial mixing capabilities by strongly buoyancy influenced turbulent convection in a vertical plane channel

Within the scope of the reactor safety research programme at the HDR-reactor blowdown-experiments shall be performed. As initial condition for these tests one aims at setting a temperature distribution which is typical for a water cooled nuclear reactor during normal operation. To this purpose the pressure vessel is fed with two mass flows of different temperatures: A hot water flow to the upper plenum and a cooler one to the lower plenum. The mixed water is removed through the annular space between core barrel and pressure vessel. The thermohydraulic behaviour of the flow in this annular space has been investigated with the three-dimensional time-dependent direct numerical simulation code for turbulent channel flows TURBIT-3. This report summarizes the extensions of the programme to include buoyancy effects, especially in the subgrid-scale models employed. (orig.)