Harmonic-Balance-Based Code-Coupling Algorithm for Aeroelastic Systems Subjected to Forced Excitation

Aeroelastic systems may exhibit vibrations that are induced by a forced periodic motion of their elements. For example, the forced periodic motion of an aileron on a deformable wing produces vibrations of this wing. Accurate numerical simulation of such problems is usually based on a time-marching scheme and a code-coupling strategy. Such computations are costly, since before the periodic-vibration cycles, a long transient has to be computed. A technique called time-harmonic balance has been developed in the field of computational fluid dynamics to accelerate the computation of unsteady periodic flows. This technique allows the periodic state of these flows to be computed directly without computing their transients. In this paper the time-harmonic-balance strategy is applied to an aeroelastic solver consisting of two coupled codes. The time-harmonic-balance technique allows the resulting aeroelastic solver to compute the periodic-vibration cycles caused by a periodic forced motion directly, without computing the long transients. The time-harmonic-balance-based aeroelastic solver is analyzed and validated on a two-dimensional aeroelastic pitch-plunge airfoil undergoing a forced pitching. Furthermore, application to an industrial case is considered, where the flexibility of an aircraft wing is taken into account in the computation of unsteady aerodynamic forces caused by an oscillating aileron.