Unsteady aerodynamic analysis of multiple interfering surfaces in subsonic flow

Abstract

Prediction of unsteady aerodynamic loads is still the most challenging task in flutter aeroelastic analysis. A number of researches have been carried out worldwide to increase the efficiency and accuracy of estimation methods for a large number of configurations ranging from thin airfoils to full-scale configurations. This research presents a procedure to predict unsteady aerodynamic loads of multiple interfering, lifting surfaces oscillating in subsonic flows. The present method is based on approximate approach to evaluate cylindrical functions occurring in the kernel function relating the aerodynamic pressure and normal wash velocity. To increase the accuracy of the method, the integration region of the kernel function is divided into two fields namely near and far, where a nonlinear regression curve fitting technique is adapted to approximate the integral part of the cylindrical function of each region. The resulting approximation results are compared, for planar surfaces, with those of other methods developed by other researchers. The present approach offers an increase in the accuracy compared to other methods. It increases the accuracy of the Epsteins-Bliss approach from originally at the maximum error of 0.0155 to 0.000161. A special numerical scheme is designed that significantly reduces the computational time. The algorithm of the procedure is presented along with the results and comparison with other methods. The recommendation and suggestions can act as a basis for a focused research in future.