Correction of aerodynamic influence matrices for transonic flow

Abstract

The authors present a novel correction approach for the doublet-lattice method in this paper. The doublet-lattice method is a standard tool for calculating unsteady aerodynamic loads in aeroelasticity. It solves the linear potential equations and is thus valid only at subsonic flow conditions. Hence, corrections have to be applied for transonic flow. The proposed correction method, CREAM (CorREction of Aerodynamic Matrices), uses surface pressure distributions obtained using computational fluid dynamics (CFD) simulations for the correction. It is based on a Taylor expansion of the aerodynamic influence coefficient matrix, where the Taylor coefficients are corrected successively. The approach can be applied to quasi-steady as well as to unsteady aerodynamic calculations. The method is demonstrated on the AGARD LANN wing at transonic attached flow conditions and compared to linearized unsteady CFD computations. Two different correction orders are examined: a ‘‘zeroth order correction’’ with a quasi-steady CFD sample as correction input and a ‘‘first order correction’’ with an additional unsteady CFD sample. It is shown that CREAM gives improved results for small reduced frequencies, where the first-order correction is always superior to the zeroth order correction.