Buffet boundary prediction using RANS-based criteria and adjoint methods

Abstract

In this work a procedure is proposed for a fast estimate of the transonic buffet boundary on aerofoils and wings. This algorithm aims to be an alternative to unsteady computational fluid dynamics simulations that are prohibitively expensive for complex flow cases. The algorithm combines steady Reynolds-averaged Navier-Stokes simulations with an adjoint method. Reynolds-averaged Navier-Stokes simulations were used to determine the buffet onset by means of suitable criteria, while the adjoint method was used to compute the sensitivities of the buffet parameters to the flight conditions, and draw the buffet boundary. The procedure was tested for two-dimensional configurations with available experimental data and for two different criteria. Particular attention was paid to the efficiency of the method and its ability to reduce computational cost with respect to purely RANS criteria for buffet boundary estimation. Possible variations to the procedure were also discussed in the results section together with the effect of some key parameters of the proposed algorithm.