A boundary element method for the aerodynamic analysis of aircraft in arbitrary motions

Abstract

A new boundary integral formulation for the aerodynamic analysis of an aircraft (in particular, a tiltrotor) in arbitrary motion is presented. The formulation is based on the velocity potential for compressible flows, and as such is an extension of past work of the authors. The distinguishing feature is that the boundary integral representation is written for a surface in arbitrary motion with respect to a frame of reference which in turn moves in arbitrary motion with respect to the undisturbed air. Thus, the integrals are evaluated on the emission surface, which is the locus of the emitting points at the locations (in the moving frame) that they had when the signal influencing a given point at a given time was emitted. The differences with respect to related formulations (e.g., Ffowcs Williams and Hawkings) are outlined. Also, the advantages of the present formulation with respect to the preceding ones by the authors are discussed. Numerical validation results are presented for the limited case of helicopter rotors in hover.