Numerical Simulation of the Flow around Helicopters

This paper presents an overview of recent activities in CFD research conducted within cooperations between DLR and ONERA for the simulation of helicopter aerodynamics. These activities are mainly illustrated by two topics in the frame of a previous 3-year bilateral cooperation on "Rotorcraft CFD code Development", the objective of which was the assessment, comparison and further improvement of the DLR and ONERA Euler/Navier-Stokes methods for the prediction of the flow around isolated helicopter rotors. The first topic is devoted to a comparison of two different grid strategies for time-accurate inviscid computations of multibladed rotors in forward flight from the solution of Euler equations: the moving grid approach by ONERA and the overlapping grid technique by DLR. The second topic is concerned with a comparison of respective Euler/Kirchhoff aeroacoustic methods for the prediction of High Speed Impulsive noise of rotors. For the assessment and improvement of Navier-Stokes methods for fuselage drag prediction, a comparison between DLR and ONERA Navier-Stokes solutions achieved within the prediction phase of the ending Brite/EuRam european project "HELIFUSE" is also presented. The paper is concluded by a summary of on going DLR and ONERA research activities in the frame of the new long-term project "CHANCE" (Complete Helicopter AdvaNced Computational Environment) for the development and assessment of common french-german CFD tools for the complete helicopter accounting for trim and dynamics.