Determining unsteady aerodynamic loads accurately and efficiently

A good preparation for solving supersonic and hypersonic flutter problems is provided. Flutter calculations require unsteady aerodynamic loads; but, with available methods, either the computation time required is too much or the calculated unsteady loads are not sufficiently accurate. We propose a method that can calculate unsteady loads accurately and efficiently. Unsteady CFD (computational fluid dynamics) technology can compute accurately unsteady loads but requires too much time. Piston theory can calculate unsteady loads efficiently but the accuracy is insufficient. We like the feature of efficiency of piston theory and retain this feature in the local piston theory which we propose and describe in detail. The local piston theory that we propose is combined with steady flow field to calculate unsteady loads efficiently. This paper describes in detail how to combine local piston theory with steady flow field. A large amount of calculation for a numerical example is given and the results show preliminarily that, after a steady flow field is known, the time needed to calculate accurately a 3D dynamic response is no more than one minute.