Simulating atmospheric boundary layer flow around a wing

This talk will present a method to simulati the turbulent flow around a 3D-wing. For the simulations the compressible flow solver TAU is used which is developed by the German Aerospace Center DLR. In the model domain two grids are combined by using the chimera technique. The primary grid is the unstructured body-fitted grid that contains the wing and the secondary grid is a cartesian grid upstream of the wing on which the turbulent flow is simulated. The cartesian grid is moved towards the wing and in a short distance in front of the wing the grid is stopped and the turbulent flow is passed to the primary grid where it can interact with the wing, simulating the flight of the wing through a turbulent wind field.

The flow model does not contain the earth surface. Therefore there is no source for atmospheric turbulence in the model. That means that the simulation has to be initialised with an already turbulent wind field. To create such a turbulent flow field a synthetic turbulence generator is used that takes the statistics of measurement data from the atmospheric boundary layer and generates a three-dimensional wind field with the same statistics. The statistics used as input comprise the energy spectrum, the correlation matrix and the variances. In the future the turbulence generator will also be able to consider coherent structures of the turbulent flow in a convective boundary layer.

This simulation strategy makes it possible to simulate the flight of a wing through realistic atmospheric boundary layer conditions, accounting for different weather scenarios. Especially during flights with high angle of attack and at low altitudes it is of interest to investigate how the angle of stall is influenced by the turbulent flow in the atmospheric boundary layer and which scales of the turbulence have an significant effect on the lift and drag produced by the wing.

The talk will cover the simulation strategy with TAU and the generation of the synthetic turbulent wind fields based on measurements. Furthermore, results from simulations will be shown and discussed.