The need for wings that can be stored in a relatively small volume and then have the capability to be unfolded, inflated, or by other means extruded to a significant span has been an area of growing interest, particular with regard to small ummanned aerial vehicles (UAVs). The Big Blue project at the University of Kentucky has conducted numerous flight tests using UAVs with inflatable airfoils supplied by ILC Dover. Due to their construction, the wing profiles associated with these inflatable wings are bumpy compared to ideal wing profiles. Wind tunnel tests at low Reynolds numbers have suggested that the bumpy surface may provide improved aerodynamic characteristics at lower speeds. The incorporation of bumps on these smooth airfoils tends to delay the onset of separation which would typically cause an increase in drag and a decrease in lift on the ideal airfoil.

The focus of this paper is to investigate the effects of the bumps through a range of angles of attack and Reynolds numbers. The airfoil profiles considered are those employed by the Big Blue project. Using an incompressible overset structured grid code, the flow over both the smooth and bumpy variants of the airfoil are investigated numerically. The numerical investigation includes possible transition and turbulence effects as well as purely laminar simulations. Current comparisons indicate qualitative agreement with experimental results, notably significant reduction of the separation region for the bumpy airfoil compared to the smooth airfoil profile.