Aerodynamic Effects of End Plates on Biplane Wings

The aerodynamic performance and associated flow physics of box wings at low Reynolds number as a function of variation in gap and stagger were experimentally investigated. To reduce the experimental parametric space for flow physics investigations, a set of cases were strategically selected based on results from a vortex lattice study. The effects of gap and stagger appear to be the dominating effects for biplanes joined at the tips by endplates; Gap was found to have the greatest effect and stagger the second greatest effect on the aerodynamic performance of a biplane with endplates using both inviscid computational and experimental techniques. Efforts to discern the optimal balance between reduced lift induced drag due to the presence of the endplate and additional skin friction drag also due to the presence of the endplate are ongoing. Several areas were identified where the integrated force results did not agree well with the inviscid computational model. These areas will be subsequently further investigated using PIV in the Treffitz plane and streamwise near wake to determine whether or not the difference truly come from viscous effects. Initial attempts at using PIV to determine drag through momentum integral methods have had mixed results; however it is likely most of the problems encountered can be eliminated using suggestions discussed above. Ultimately, a combination of vortex lattice method, integrated force measurement, streamwise PIV, and Treffitz plan Stereo PIV will be used to better characterize the flowfield behind biplane lifting surfaces in an attempt to determine the configuration with the optimal aerodynamic performance. These results will be subsequently used in an effort to potentially exploit any beneficial effects identified in other configurational contexts