REDUCED ORDER MODELLING OF GUST ANALYSIS USING COMPUTATIONAL FLUID DYNAMICS

The simulation of gust responses is a crucial task in the design and certification process of a new aircraft. Moreover, if high accuracy is desired, the computational cost can be overwhelming. Linear frequency-domain methods have previously shown significant reduction in computational cost for motion-induced aerodynamics as well as for gust excitations. Time-domain signals are reconstructed by a superposition of responses at several discrete frequencies. Rather than using the frequency-domain method directly, a reduced order model is constructed projecting the time-depending linearised Reynolds-averaged Navier-Stokes equations on a basis obtained by proper orthogonal decomposition. The resulting small-sized ordinary differential equations for the modal coefficients are integrated in time. Results are presented for a two-dimensional NACA 0012 aerofoil covering sub- and transonic conditions including a case with shock-induced separation. Responses due to 1-cos as well as to sharp-edged gusts are compared between the reduced order model and its non-linear full order counterpart showing time histories of the lift coefficient and worst case surface pressure coefficients.