Comparison of a Strong and a Weak Coupling Scheme for Aeroelastic Computations of a Rotor with Double-Swept Blades

Abstract

High-fidelity aeroelastic simulations of rotor systems are carried out by coupling solvers of computational fluid dynamics (CFD) and a multibody system (MBS) with each other, namely the DLR Tau-Code and Simpack. In order to achieve this, aerodynamic forces and structural displacements on the blades as well as rigid body motions are exchanged between both solvers. Considering a strong coupling scheme, data is exchanged after each physical time step which makes it suitable for the use in time-transient simulations. While seeking for a periodic steady-state, e.g. a helicopter in forward or hovering flight, the precise simulation of transients is of minor importance. With this in mind, the wall-clock time of the simulation chain can be minimized by reducing the overhead resulting from frequent data exchange and extensive switching between both solvers. The implemented method is characterized by a weak coupling scheme which denotes a data exchange of an entire rotor revolution. In addition, the coupling window is phase-shifted after each iteration step by choosing an additional phase added to the end of one rotor revolution. It is applied to a model rotor with double-swept blades. In the end, a comparison for the blade tip displacement was made with results from a strong coupling scheme showing different curves, mainly with regrad to the peak values in the transition phase from up- to downstroke.