CDF code validation of rotor/fuselage interaction using the commercial software STAR-CCM+8.04
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Monday, July 1, 2013

In this paper the commercial CFD software package STAR-CCM+ 8.04 was validated against wind tunnel experiments and a qualitative comparison to a non-commercial code was made. NASA’s generic ROBIN helicopter model was adopted for transient simulations to study Rotor-Body interaction (ROBIN). Two different CFD methods have been applied to model the main rotor rotation and the cyclic blade pitching. The first method uses a sliding interface approach where the volume around the entire rotor is modelled in a cylindrical region with a rotating mesh. The cyclic blade pitching has been modelled with a morphing mesh inside that rotating mesh region. The second method uses an overset grid approach where the volume around each blade is modelled in an individual overset grid region. In both methods the rotor rotation is resolved with 1 degree per timestep. The compressible ideal gas flow is solved with a classical Reynolds-Averaged-Navier-Stokes (RANS) solver by implicit spatial integration in an unsteady analysis, using a coupled algebraic multi-grid method with a courant number of CFL = 30. Turbulence is modelled with the well known SST (Menter) K-omega model with 2nd order convection. The helicopter is in straight forward flight with an advance ratio of μ = 0.15. Computational results were compared to NASA’s existing experimental results. In the simulations the results became quasi periodic between the 2nd and 3rd rotation; 5 full rotor rotations were simulated. It was concluded that computational results for both motion modelling methods were in good agreement with unsteady pressure measurements at various locations along the fuselage. Along the top centreline over the nose and tail boom the periodic pressure fluctuations induced by the blade passages over one full rotor rotation were in good agreement with the experiments. In accordance with the experiments it was also found that the magnitude of the pulse increases with the thrust coefficient. The CFD simulations revealed detailed flow features surrounding the rotor and the fuselage. Detailed sections of the vorticity field and isosurfaces of the q-criterion reveal the propagation of the blade tip vortices until far downstream of the fuselage. This flow structure is also in good agreement with computational results from studies carried out with non-commercial CFD codes. The method presented using STAR-CCM+ 8.04 is capable to model the complex motion of helicopter rotor blades and predict the flow field and is a promising tool for future analysis of helicopter aerodynamics.

Author Name: 
Boris Kubrak
Deryl Snyder
Author Company: