A maximum curvature method for predicting transonic buffet onset based on steady aerodynamic parameters

It is difficult to predict the buffet onset by kink analysis in steady aerodynamic parameter curves such as the lift coefficient curves, pitching moment coefficient curves and trailing edge pressure coefficient curves at a certain flow conditions. Thus, a maximum curvature method is proposed which is based on the aerodynamic parameter data, to find the buffet onset point at which the curve curvature achieves an extreme. The method is to fit a fourth order polynomial using the aerodynamic parameter data calculated by steady N-S equation. Subsequently, curvature analysis is carried on with the fitted curve and the stationary point in a particular interval of the curve is obtained. And this point is regarded as the buffet onset point. This method can be applied to predict the transonic buffet onset for airfoils based on steady aerodynamic parameters and good agreement is achieved with the comparison of predicted results and wind tunnel test data.