Loosely Coupled CFD/CSD Simulations of Helicopter Rotors in Forward Flights

A loosely coupled simulation is presented for a helicopter rotor in forward flight. The aeromechanical performance of the Bell 427 main rotor is analyzed at 140 knots using the computational fluid dynamics (CFD) code U2NCLE coupled to the computational structural dynamics (CSD) code DYMORE. A loose CFD/CSD coupling strategy is detailed for stable and efficient analysis of helicopter rotors in level, forward flight. The CFD solver uses a free wake model to capture multi-blade effects with a single blade model. In order to account for the blade motion and structural deformation, a robust mesh deformation method based on a radial basis function is used for rotor surface and volume grid deformation. The numerical results indicate that improved airload predictions can be obtained by using high fidelity CFD simulations coupled with the CSD code, as compared with the built-in CSD aerodynamic model.