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Steady and oscillatory convection in a rectangular box heated from below are studied by means of a numerical solution of the three-dimensional, time-dependent Boussinesq equations. The effect of the rigid sidewalls of the box on the spatial structure and the dynamical behaviour of the flow is analysed. Both conducting and adiabatic sidewalls are considered. Calculated streamlines illustrate the three-dimensional structure of the steady flow with Prandtl numbers 0.71 and 7. The onset and the frequency of the oscillatory instability are calculated and compared with available experimental and theoretical data. With increasing Rayleigh number a subharmonic bifurcation and the onset of a quasi-periodic flow can be observed. A comparison of the different time-dependent solutions shows some interesting relations between the spatial structure and the dynamical behaviour of the confined flow.

DLR's incompressible flow solver THETA is introduced for wind turbine applications on the isolated NREL phase VI Unsteady Aerodynamic Experiment rotor. The optimization of parameter settings for the prediction of attached and separated flows on the rotor is performed, including time step size, spatial discretization scheme, turbulence models and Chimera overset grid technique. Afterwards, a systematic study on the pressure distributions, rotor thrust and rotor torque for experimental series S, I and J is performed. The accuracy of results for wind velocities between 7 and 25 m s 1 , covering attached, partly separated and deep stalled flow conditions, is discussed. While good to excellent agreement between THETA sectional pressure distributions and the experimental reference data is achieved in attached flow and deep stall configurations, more efforts are needed to predict partly separated flow cases with comparable accuracy. A code-to-code comparison with DLR's compressible flow solver TAU enabled the quantification of differences in pressure prediction because of the use of incompressible and compressible flow solvers.

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