High-precision prediction on unsteady aeroelastic loads of helicopter rotors under blade-vortex interaction condition

In order to obtain accurate aerodynamics loads of helicopter rotors under complex blade-vortex interaction (BVI) condition, blade deflections were introduced into rigid rotor CFD analysis and a computational fluid dynamics/computational structural dynamics (CFD/CSD) coupling method suitable for aerodynamic characteristics analysis of elastic rotors under BVI condition was developed. The CFD module solved Reynolds averaged Navier-Stokes (RANS)/Euler equations based on dual time-stepping algorithm and Baldwin-Lomax (B-L) turbulence model. The CSD module employed finite element model of moderate deflection beam theory, and the blade equations of motion were calculated by using Newmark-Beta method. Blade deformations were accomplished through algebraic grid deformation method and a CFD/CSD coupling strategy was developed for exchanging fluid/structure information. The established CFD and CSD modules were validated by UH-60A elastic blade respectively, and aerodynamics loads of UH-60A rotor were analyzed under BVI condition and compared with flight test data. The calculated results demonstrated that coupled CFD/CSD method can acquire more accurate aerodynamics loads under BVI condition than lifting-line method in rotor comprehensive analysis and rigid rotor CFD method, and the flow phenomena near azimuth of advancing blade and azimuth of retreating blade under BVI condition are well captured in detail. The calculated results of the lift's phase and amplitude caused by BVI agree well with the experimental data. ©, 2015, BUAA Press. All right reserved.