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Morphing wings comprised of fixed leading sections with piezocompositetrailing control surfaces have emerged as a novel active control technique forunmanned aerial vehicles. However, the wake dynamics and aerodynamicperformance of such hybrid airfoil configuration has not been thoroughlyinvestigated. In this paper, direct numerical simulations of two-dimensionalflows over hybrid airfoils comprised of NACA 0012 leading sections withpiezocomposite trailing control surfaces are performed at a fixed Reynoldsnumber of 1000. The effects of length and camber of the trailing controlsurface on the laminar aerodynamic characteristics are studied over a widerange of angle of attack. It is shown that the flow behind the airfoil exhibitsdifferent features, including steady flow, periodic vortex shedding, andquasi-periodic vortex shedding for different configurations. The transitionbetween these wake states occurs at slightly smaller angles of attack comparedto the nominal NACA 0012 airfoil. While the drag coefficient remains close toeach other at a fixed angle of attack, the lift coefficient of the hybridairfoil is positively affected by the length and camber of the trailing controlsurface. The mechanism of lift generation is examined by surface pressuredistributions and a force element analysis. It is revealed that with increasedcamber of the trailing control surface, the flow on both the suction andpressure sides of the airfoil are modified in a beneficial way to enhance lift.Increasing the length ratio only significantly modifies the flow near the aftsection on the pressure side. The results herein provide a laminar aerodynamiccharacterization of hybrid airfoils with trailing control surfaces, and couldpotentially aid the design of control techniques for next-generation smallunmanned aerial vehicles.

Low-Reynolds-number aerodynamic characteristics of airfoils with piezocomposite trailing control surfaces