Active aeroelastic alteration to reduce off-design induced drag

Abstract

Whereas aeroelastic tailoring is known to make one particular design point optimal, active aeroelastic alteration (AAA)--application of Active Aeroelastic Wing (AAW) technology using multiple wing-edge control surfaces to turn aeroelastic twist of flexible wings to net benefits--can make up actively any off-design point of interest to be optimal as well. Active distribution-based Drag Reduction Control (ADRC) is such an AAA problem that uses Kolonay and Eastep's strip-forces-and-strip-coordinates expression of induced drag as the minimization objective. Trying to solve this problem using ASTROS, MSC. NASTRAN, or another NASTRAN-based multidisciplinary design/analysis software will encounter inconveniences in obtaining required sensitivity data and in performing required trim optimization. This paper presents analytic solution techniques that render both the sensitivity evaluations and the optimization calculations natural and convenient. Two strategies combine to resolve the inconveniences and enable in-process non-iterative trim optimization and analytic sensitivity evaluation without a need to exit the specific NASTRAN-based multidisciplinary design/analysis system used. The AAA solution techniques are demonstrated by results of initial test on a classical forward-swept-wing example. Test results also demonstrate that in direct induced-drag minimization, imposing gap limitation on adjacent control-surface deflections is both beneficial and necessary.