22-10-2012, 03:49 PM
On the Application of Contour Bumps for Transonic Drag Reduction(Invited)
ABSTRACT
The effect of discrete contour bumps on reducing the transonic drag at off-design conditions on an airfoil have been
examined. The research focused on fully-turbulent flow conditions, at a realistic flight chord Reynolds number of 30 million.
State-of-the-art computational fluid dynamics methods were used to design a new baseline airfoil, and a family of fixed
contour bumps. The new configurations were experimentally evaluated in the 0.3-m Transonic Cryogenic Tunnel at the NASA
Langley Research center, which utilizes an adaptive wall test section to minimize wall interference. The computational study
showed that transonic drag reduction, on the order of 12% - 15%, was possible using a surface contour bump to spread a
normal shock wave. The computational study also indicated that the divergence drag Mach number was increased for the
contour bump applications. Preliminary analysis of the experimental data showed a similar contour bump effect, but this data
needed to be further analyzed for residual wall interference corrections.