Paper Presented at AIAA Conference (5/6/2006)
Dr. Sinha presented a paper entitled
Drag Reduction of Natural Laminar Flow Airfoils with a Flexible Surface Deturbulator
at the 3rd AIAA Flow Control Conference on June 5-8, 2006 in San Francisco, California.
This paper gives an overview of Dr. Sinha's flight test results. The abstract reads:
A flexible composite surface deturbulator (FCSD) has been developed in order to
stabilize large extents of thin separated flow over aerodynamic surfaces through passive
interactions with a streamwise varying pressure gradient boundary layer flow. This
accelerates the external flow since skin friction is mitigated, while attenuating turbulent
dissipation in the separated region. In this study this effect has been used to reduce drag and
increase lift of natural laminar flow airfoils at low Mach numbers with Reynolds numbers
ranging from 3x105, which is typical of long endurance unmanned aerial vehicles, to 6x106
typical of many general aviation aircraft. Wing profile drag reduction of 10-20% was
observed in high-Re flight tests with a NLF-0414F wing. Low-Re wind tunnel measurements
on the NLF-0414F have shown a profile drag reduction of 60-80% including a 45%
reduction in pressure drag, along with a 12% increase in section lift coefficient. This doubled
the L/D from 12.5 to 25.7. A full-span upper surface FCSD treatment of an earlier
generation Wortmann FX-S-02196 natural laminar flow wing indicated a 5-20% increase in
total aircraft L/D over the range of flyable airspeeds.
For a PDF copy of the full paper, click AIAA-2006-3030-245.