Implementation and Validation of an Actuator Disc Boundary Condition for Helicopter Rotors into the Hybrid DLR RANS Solver TAU

Kurzfassung

Motivated by the demand for a fast flow simulation tool that takes the interaction between rotor and helicopter fuselage into account this thesis is about the extension of an actuator disc boundary condition in the unstructured DLR TAU code. Different modelling approaches are presented where the source term approach, which has already been implemented in the structured DLR FLOWer code, is most suited for rotors in forward flight. Numerics of the source term approach as well as topics touched by the implementation such as time step determination, smoothing, dissipation and low Mach number preconditioning are discussed. The concept of the FLOWer implementation is carried over into the unstructured TAU framework where modifications in preprocessor and solver are outlined. Comparing propeller mode results from TAU to 1D momentum theory shows excellent agreement. This is also observed for rotor in forward flight results between FLOWer and TAU. Finally, the EC145 helicopter demonstration case with two actuator discs shows the robustness of the implementation.