Self correcting wind tunnels

Abstract

One of the early triumphs of the Lanchester-Prandtl wing theory was that it explained the effects of wind tunnel boundaries and provided explicit and simple formulae to correct wind tunnel measurements for these effects. As every aerodynamicist knows, this theory tells us, with the help of “images”, that the boundaries, in the presence of a lifting wing, produce extraneous velocity components in the flow. At least two generations of experimenters have routinely corrected their angles of attack and their measured drag values for the presence of the vertical component.