When Do Endplates Work?

Abstract

The effect of the gap between endplates and wing sections on aerodynamic lift and drag forces was investigated. This was studied in order to determine the maximum gap distance at which flow can still be considered two-dimensional, and tip effects can be neglected. A non-dimensional distance, λ, was defined as the ratio of gap distance, d, to laminar boundary layer thickness, δt,laminar , over the endplate. Force balance measurements were taken for a NACA0012 wing section placed between two endplates at the Dryden Wind Tunnel facility. λ was varied for desired values of λ = {0.5, 0.75, 1.0, 2.0, 3.0, 4.0} and data was taken at two different desired Reynolds numbers,Re = 50k & 100k for angles-of-attack, −10◦ ≤ α ≤ 10◦. Problems were encountered with the test apparatus and imperfections were noticed on the wing surface. However, considering a single, reliable data set atRe = 50k, the critical non-dimensional gap distance was determined to be λcritical = 1.0± 0.1, for the given airfoil. Given the widespread implications of such an investigation to wind tunnel testing, further experimentation is required.