Conservation Issues for Reynolds-Averaged Navier-Stokes–Based Rotor Aeroelastic Simulations

Abstract

Aeroelastic simulations that are computed by coupling separate computational fluid dynamics (CFD) and computational structural dynamics (CSD) codes will include not only numerical errors in both the CFD and CSD methods, but also errors associated with the data exchange among the codes of the aerodynamic loads and moments and structural deflections. Whereas the numerical errors associated with the data interface have been investigated and quantified for fixed-wing applications, their effect has not been quantified for rotational applications, such as rotors and wind turbines, in which rigid body degrees of freedom cannot be separated from flexible motion of the blades. This paper provides a systematic analysis of the numerical errors introduced by the data interface for high-aspect ratio blades undergoing multibody dynamic motion including rotation. It is demonstrated that the failure to consider conservation of work or energy during the CFD-CSD data exchange can lead to a shift in the mean loading as observed for fixed-wing applications and an alteration of the controls necessary to achieve rotor trim affecting the rotor performance prediction. Various techniques to obtain minimal data transfer errors on a given grid are examined. Data transfer on unstructured CFD meshes appear to be more sensitive than the process on structured CFD meshes.