CFD Analysis on the Main-Rotor  Blade ofa Scale Helicopter  Model using Overset Meshing

Sammanfattning: In this paper, an analysis in computational uid dynamics (CFD) is presented on a helicopter scale model with focus on the main-rotor blades.The helicopter model is encapsulated in a background region and the ow eld is solved using Star CCM+. A surface and volume mesh continuum was generated that contained approximately seven million polyhedral cells, where the Finite Volume Method (FVM) was chosen as a discretization technique. Each blade was assigned to an overset region making it possible to rotate and add a cyclic pitch motion. Boundary information was exchanged between the overset and background mesh using a weighted interpolation method between cells. An implicit unsteady ow solver, with an ideal gas and a SST (Mentar) K-Omega turbulence model were used. Hover and forward cases were examined. Forward ight cases were done by changing the rotor shaft angle of attacks and the collective pitch angle 0 at the helicopter freestream Mach number of M = 0:128, without the inclusion of a cyclic pitch motion. An additional ight case with cyclic pitch motion was examined at s = 0 and = 0. Each simulation took roughly 48 hours with a total of 96 parallel cores to compute. Experimental data were taken from an existing NASA report for comparison of the results. Hover ight coincided well with the wind tunnel data. The forward ight cases (with no cyclic motion) produced lift matching the experimental data, but had diculties in producing a forward thrust. Moments in roll and pitch started to emerge. By adding a cyclic pitch successfully removed the pitch and roll moments. In conclusion this shows that applying overset meshes as a way to analyze the main-rotor blades using CFD does work. Adding a cyclic pitch motion at 0 = 5 and s = 0 successfully removed the roll and pitching moment from the results.