Mesh deformation method for rotor flows

Helicopter blades experience large in-flight deformations that affect the aerodynamics of the rotor. Consequently, computational fluid dynamics (CFD) methods applied to helicopter flows must have appropriate algorithms to account for the blade deformation without deterioration in the CFD mesh quality. In this work, a hybrid mesh deformation method, suitable for use with helicopter blades, is proposed. The method begins by accounting for the blade deformation using a modal structural model. The interpolation between the finite element and CFD meshes for the blade surface is based on the constant-volume tetrahedron method and is combined with transfinite interpolation as well as the spring analogy method. The final algorithm is efficient and resulted in deformed meshes with good qualities. A range of rotor cases were considered, and the changes in volume of the CFD cells were less than 30% of their original values. The cell skewness was also kept at acceptable levels. The mesh deformation method was coupled with the helicopter multiblock CFD solver, and computations were undertaken for rigid and deformed blades. It was found that the structural deformation affected the blade loads even for hovering rotor cases, although it had a more pronounced effect in forward flight. The mesh method was efficient and accounted for less than 1% of the total central processing unit time