Aerodynamic Characterization of Multiple Wing-Wing Interactions for Distributed Lift Applications

Date of Award


Degree Name

M.S. in Aerospace Engineering


Department of Mechanical and Aerospace Engineering


Sidaard Gunasekaran


There has been a recent surge in the need for unmanned aerial vehicles (UAVs), drones, and air taxis for a variety of commercial, entertainment, and military applications. New aircraft designs put forth by companies have shown to feature multiple lift producing surfaces and rotors acting in proximity to each other. These configuration choices are primarily informed by the “compactness” requirement in the design. For this reason, configurational choices are being considered that would otherwise not receive attention. Multi-wing configurations or distributed lift systems become a compelling choice in conceptual design of future UAVs and private air vehicles (PAVs) that complements the vertical takeoff and landing capabilities of the design. For multi-wing configurations to be considered in the early conceptual design process, the reliability of traditional lower order aerodynamic methods in predicting these aerodynamic effects must be determined. However, the nature of a highly distributed lift configuration, with 10 or more lifting surfaces in close proximity, does not lend itself to rapid or accurate viscous numerical solution. Moreover, highly distributed lift configurations drive individual lifting surface Reynolds numbers into a range where viscous interactions could have a profound effect on aerodynamic performance. As such, the degree of dependence of wing-wing interactions due to viscous effects could be determined in a first iteration through a reductionist approach. Focusing specifically on the three-dimensional viscous interactions and the aerodynamic forces on the upstream and downstream wings allows for a direct determination of the importance and isolated contribution of these effects. Proximity effects due to wing-wing interactions were experimentally quantified as a function of gap and stagger across a wide range of different relative angles of attack (décalage). The proximity effects and the zone of influence at different gap and stagger locations were systematically characterized through measurement of the changes in aerodynamic force coefficients of individual wings and the combined wing-wing system. The wing angle of attack combinations that maintain similar aerodynamic efficiency at different gap and stagger locations were determined to allow for optimal placement of wings in a distributed lift system. All experiments were conducted at the University of Dayton Low Speed Wind Tunnel (UD-LSWT) on two, three, and four Clark-Y AR 2 semi-span wings. Numerical investigations were conducted to validate FlightStream, a potential flow solver, with experimental results to use as a tool to extract more information about the flow physics and to simulate further configurations without the need of conducting wind tunnel tests. All the analysis techniques were done on the two, three, and four-wing studies to determine a wide range of beneficial and detrimental combinations of gap, stagger, and décalage along with an overall conclusion about the effect of the number of wings on these configurations.


Experimental Aerodynamics, Wing-Wing Interactions, Multi-Wing Aircraft, Distributed Lift, Unmanned Aerial Vehicles, Aircraft Design, Wind Tunnel Testing, Potential Flow Solvers

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