The Aerodynamic Performance of the Houck Configuration Flow Guides

In an effort to explore efficient wing designs for UAV's, the Air Force is investigating the patented Houck Aircraft Configuration, which is a joined-wing aircraft with curved flow guides of varying camber connecting the upper and lower wingtips. Models were drawn in three-dimensions using Solidworks with upper and lower wings drawn as identical NACA 2412 airfoil sections for all models. A variety of airfoil sections between the upper and lower wingtips were drawn and rotated to achieve a combination of cant and angle of attack variation. Subsequently, a solid part was lofted through these sections and merged with the upper and lower wings. Each model was built by a rapid prototype machine. A six-component balance in the AFIT low-speed wind tunnel provided measurements yielding the aerodynamic data of each model. Comparisons are made to the same basic planform area without flow guides and to a case where the wingtips are joined with a flat plate. At a Reynolds number of 38K, the increase in skin friction drag outweighed any possible reduction of induced drag. However for Reynolds numbers in the 57K to 120K range, improvements in L/Dmax of about 2-5% over the no flow guide case were measured.