Effects of Structural Properties on Rotor Airloads Prediction Based on CFD/CSD Coupling Method

For accurate aeroelastic analysis, the unsteady rotor flowfield is solved by Computational Fluid Dynamics (CFD) module based on RANS/Euler equations and moving-embedded grid system, while Computational Structural Dynamics (CSD) module is introduced to handle blade flexibility. In CFD module, dual time-stepping algorithm is employed in temporal discretization, JST scheme is adopted in spatial discretization and B-L turbulent model is used to introduce the viscous effect. The CSD module is developed based on Hamilton's variational principles, moderate deflection beam theory and advanced geometric blade-tip analysis. Grid deformation is implemented using algebraic method through coordinate transformations to achieve deflections with high quality and efficiency. A CFD/CSD loose coupling strategy is developed to transfer information between rotor flowfield and blade structure. The CFD and CSD module is validated respectively, then the CFD/CSD loose coupling is adopted in airloads prediction of UH-60A rotor under high speed forward flight condition and the calculated results are compared with test data which show good agreements. Finally, effects of torsional stiffness properties on airloads of rotors with different tip swept angles (from 10 degree forward to 30 degree backward) are investigated. The results are evaluated through pressure distribution and airloads variation, and some meaningful conclusions about the moderated shock wave strength and pressure gradient caused by varied tip swept angle and structural properties are drawn.