Parametric Evaluation of Deployable Serrated Flaps on a Representative UCAV Configuration

Abstract

A parametric investigation of the Deployable Serrated Flap (DSF) was tested for air vehicle flow control on a representative 4% Uninhabited Combat Air Vehicle (UCAV). Single, Tandem, and Tandem In Opposition Deployable Serrated Flaps were tested to establish the effect on air vehicle performance. The chordwise and spanwise location, flap length, flap height, flap deflection angle, serration effect, tandem flap spacing, and tooth alignment were varied to maximize lift-over-drag ratio and maximum lift coefficient at a local angle of attack. A six-component internal balance measured the aerodynamic forces and moments at a tunnel dynamic pressure of 43.3 psf. The results showed that the Tandem DSF and Tandem DSF In Opposition were most effective in increasing maximum local lift coefficient and lift-over-drag ratio, respectively. Increasing the flap height was found to greatly increase both lift coefficient and lift-over-drag. Tooth alignment had minor effects on performance. The effect of serrations was shown to increase lift coefficient but decrease lift-over-drag ratio. Locating the flaps at 0.21 y/b and for a length of 0.25 l/b were shown to offer the most aerodynamic improvement. The smallest deflected flap was seen to offer the greatest improvement in lift coefficient and lift-over-drag ratio. The largest deflected flap acted like an aerodynamic spoiler.