An Assessment of Rotor Dynamics Correlation for Descending Flight Using CFD/CSD Coupled Analysis

A correlation effort has been made using coupled computational fluid dynamics (CFD) and rotorcraft computational structural dynamics (CSD) codes to calculate the helicopter rotor blade-vortex interaction (BVI) airloads, blade deflections, and structural loads for descending flight. An iterative loosely coupled trim methodology with a low-pass filter was used to couple OVERFLOW-2 and CAMRAD II codes. Overall, the inclusion of the unsteady and three-dimensional OVERFLOW-2 aerodynamics solutions into the CAMRAD II code has improved the airloads and blade moments prediction capability on the rotor blades. The correlations included airloads, blade deflections and blade moments for the HART II and UH-60A rotors at an advance ratio of 0.15. The results of this investigation indicate that a further improvement of the correlation for the radial distribution of the elastic torsion is necessary for more accurate prediction of airloads and blade moments. An increased availability of measured blade deflection data could open a new opportunity for better correlation of the blade moments.