Subsonic source and doublet panel methods

This work presents a source and doublet surface panel method for solving unsteady subsonic flows around wing and bodies. The approach is based on Morino's theory but features three modifications. The impermeability boundary condition is defined as zero mass flux normal to the surface instead of zero normal velocity, a new methodology is introduced to calculate the aerodynamic influence coefficient matrices and the pressure distribution around the surface is evaluated using a nonlinear unsteady Bernoulli equation. The method is demonstrated on three experimental test cases from the literature; it is shown that it can predict more accurately the steady and oscillating pressure distribution around the surface than Morino's original linear approach. Crucially, the modified approach can represent asymmetries in the pressure distribution due to both asymmetric motion and shape. While higher fidelity alternatives exist for solving such flows, the present method has very low computational cost and would be suitable for optimization procedures during preliminary design, as long as the flow remains subcritical and attached at all times.