Discrete vortex method for a detached flow on a two-airfoil configuration at high angle of attack

Overview & Synopsis

Airfoils with high values of the angle of attack present detached flows, characterized by leading edge and trailing edge vortex shedding. Experiments and high-order computations contribute to the understanding of these flows, but fast low-order methods are needed for engineering tasks. In the present work, we implement a discrete-time vortex method, using a leading edge shedding criterion. For a given airfoil and Reynolds number, there is a critical value of that parameter. If the instantaneous value exceeds the critical value, vortex shedding occurs at the leading edge. In addition, the Kelvin theorem imposes for each time step, that the total circulation equals zero. That type of method, initially developed for flows around unsteady airfoils, is used to compute the unsteady flow resulting from detached airfoils at constant angle of attack. The airfoil configuration consists in two SD7003 airfoils of equal chord, placed at different stagger and gap. The study focuses on lift change produced varying the stagger between the airfoils.