Aerodynamics and aeroacoustics of wings and rotors via BEM - unsteady, transonic, and viscous effects

Recent developments on a general boundary integral formulation for the aerodynamic and aeroacoustic analyses of lifting bodies (e.g., wings and rotors) are reviewed. The emphasis is on recent numerical results, specifically on the effects of the unsteadiness, of the viscosity, and of the transonic nonlinearities. The boundary-element full-potential formulation for bodies in arbitrary motion is outlined along with the its extension to viscous/inviscid interaction. The effects of viscosity are taken into account through a coupled boundary-layer/full-potential technique similar to that used in the CFD community. Numerical results obtained with the present formulation are compared against numerical and experimental results available in literature. They include (i) aerodynamics and aeroacoustics of helicopter rotors in hover and forward flight in subsonic flows; (ii) transonic aerodynamics/acoustics results for steady potential flows around airfoils and hovering rotors, and (iii) viscous flows (subsonic and transonic) around airfoils.