Lifting Surface Tip Flows
The use of a raked tip has been shown to be a viable option for drag reduction in a manner similar to winglets. Local dihedral and sweep in the outboard tip region of a fixed wing are being studied in an effort to optimize this type of tip treatment. Parametric computational studies are underway using TetrUSS from NASA Langley. Complimentary experimental studies are being conducted to estimate lift and drag components from seven hole probe wake measurements in the Clarkson Subsonic Wind Tunnel. In particular, the impact on induced drag is being investigated as determined from the wake measurements. The wakes from small wind turbines are strongly influenced from the tip flows generated by the rotor blades and efforts to correlate the maximum power with the flowfield behavior are also being conducted experimentally.

Shear Layer Vortices
The objective of this study is to quantify the shear layer sub scale vortex structures on a delta wing. Previous investigations have indicated spatially fixed structures, which depend on the wing angle of attack and sweep, that break from the shear layer to wrap around the vortex. Flow surveys are being taken over a series of delta wings in the Clarkson Subsonic Wind Tunnel using a seven hole probe and stereo PIV.

Juncture Flows
The flow in the juncture region of two intersecting bodies can be subject to a wide range of conditions making optimal, drag reducing geomtries difficult to achieve. Tailoring of the local geometry, such as with fillets, has been done in the past to minimize the impact of the juncture flow. New geometries ideas are being explored computationally and experimentally to reduce juncture flow drag.

Publications and Reports

Lazos, B. S., and Visser, K.D., "Aerodynamic Comparison of Hyper-Elliptic Cambered Span (HECS) Wings with Conventional Configurations", AIAA-2006-3469, 25th AIAA Applied Aerodynamics Conference, San Francisco, CA., June 2006.

Visser, K.D., Ferrero Ferrero, M. del Carmen, and Nelson, R.C., "Physical Considerations of Leading Edge Flows," AIAA 2004-5083, 22nd Applied Aerodynamics Conference, Providence, RI, August 16-19, 2004.

Bennington, M.A. and Visser, K.D., "Flow Field Characteristics of an Optimized Multi-Bladed Horizontal Axis Wind Turbine", 11th International Symposium on Flow Visualization, August 9-12, 2004, University of Notre Dame, Notre Dame, Indiana, USA

Ferrero Ferrero M. De Carmen, and Visser, K.D., "Investigation of Shear Layer Vortex Structures on Delta Wings, " Clarkson Department Report No. MAE-366, July 2003 Clarkson University

Gold, N.P. and Visser, K.D., "Aerodynamic Effects of Local Dihedral on a Raked Wing Tip," AIAA-2002-0831, 40th AIAA Aerospace Sciences Meeting and Exhibit , January 14-17, 2002, Reno, NV.

Washburn, A.E.and Visser, K.D. , "Evolution of Vortical Structures in the Shear Layers of Delta Wings" AIAA-94-2317, June 20-23, 1994 Colorado Springs, CO