Impact of Modelling Approaches on the Prediction of Ground Effect Aerodynamics

This paper is about the impact of different modelling approaches on the prediction of the aerodynamic characteristics of airfoils and wings with ground effect and about the peculiarities of unsteady ground effect. Different boundary conditions on the ground wall (viscous/steady, non-viscous, viscous/moving) were applied in the performed simulations. The resulting local and global flow-related phenomena are presented and interpreted. One of the main objectives of this study is the assessment of the error that results from the different modelling approaches. Steady and unsteady panel-computations and RANS-simulations were carried out with the solver UNPAC and the Finite Volume CFD-code FLOWer. In order to separate the two- and three-dimensional effects, the first part of the study is based on a two-dimensional Clark-Y airfoil. In the second part, the aerodynamic characteristics of a wing with ground effect are presented, including three-dimensional phenomena. The data is compared to wind-tunnel data in order to verify the validity of the simulational approach. The third part of this paper deals with the features and the characteristics of unsteady ground effect as it occurs during landing approaches of aircraft, realized by a steadily decreasing ground clearance in the simulation.