Findings in Aero-Acoustic Simulations for Optimizations

The methods of the aero-acoustic optimization toolchain developed by DLR within the VicToria project are further analyzed. From previous investigations, it was settled that an unsteady panel code with a free-wake model poses a fast alternative to higher-order CFD simulations to predict blade-vortex interaction noise. In this paper, a brief validation of both methods against the HART II rotor is done. Design parametric studies with UPM are carried out for which single CFD simulations are placed to examine the correlation between both methods. In the end, an optimization with the panel code as well as CFD is conducted to see how good the final designs match. From this research it is observed that UPM captures plausible trends when altering the chord distribution. The blade sweep may be optimized with caution when using UPM. However, for the optimization of an-/dihedral, UPM predicts a very different trend than CFD. The final designs retrieved by UPM or CFD contradicted each other when optimizing with all five parameters. The reason for this mostly lies in the determination of the strength of the rolled-up tip vortex and partially its location.