In need of high lift/drag ratio design for high-speed unmanned combat aerial vehicles with the Lambda wing configuration, a wind tunnel test is conducted at Mach number 0.4 to select leading edge shapes in consideration of initial compression effect, which in fact takes place during climbout/descending stages. Flow topology over the lee side of the test model is analyzed at Mach number 0.4. Results show that leading edge shapes with a comparatively high lift/drag ratio have a consistent topological structure. Lift/drag properties at the cruise condition are investigated at Mach number 0.75. Aerodynamic forces are measured by a strain gage balance, and the oil flow technique is adopted to obtain flow patterns across the surface of the model. The visualized flow results are further used to analyze vortex formation and development within focused regions.

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