Euler Calculations of Multibladed Rotors in Hover by DLR and ONERA Methods and Comparison with Helishape Tests

Within the European project HELISHAPE, the Euler methods for the calculation of multibladed rotors in hoverflight, developed respectively by DLR and ONERA, have been compared and assessed. No wake model is used by both methods. The computations are performed as blind-test calculations on common single-block structured grids. The test cases are the HELISHAPE hover experiments with the 4-bladed 7A rotor and 7A-D1 rotor. These rotors are scaled versions of realistic helicopter rotors with an aspect ratio of 15. For all test cases the predicted pressure distributions of both codes are in good agreement. Considering that Euler calculation do not account for viscous effects the predicted surface data also compare well with experiments. A detailed comparison of the wake and tip vortex representation by both Euler methods shows some differences. The strong effects of numerical diffusion on wake resolution are demonstrated.