Experimental and Numerical Study of the Effect of Gaps on Laminar Turbulent Transition of Incompressible Boundary Layers

In this paper, the effects of gaps on the boundary layer transition are investigated on an ONERA-D airfoil both experimentally and numerically. The experiment has been conducted in a subsonic wind tunnel for several gap geometries and aerodynamic conditions. Hot-wire anemometry was used to quantify the transition modification induced by the imperfection compared to the smooth case in favorable and adverse pressure gradients. At the same time, the gap effects are numerically estimated with the help of a ΔN model previously developed at ONERA and compared to the experiment.