University of Michigan Wind Tunnel Testing

Wind Tunnel Testing Performed

Initial aerodynamic testing of the MACW was conducted at both The Ohio State University's and University of Michigan's low speed wind tunnels in 2003. The major focus of the wind tunnel aerodynamic testing was to verify that a properly shaped variable geometry trailing edge can minimize the airfoil drag level over a wide range of lift production. Aerodynamic data was recorded for flap deflections between -10° and +10° in two-degree increments, through -4° to +10° airfoil angle-of-attack. All testing was conducted at a wind tunnel velocity of 0.12 Mach (130 ft/sec). Test Reynold's number, based on model chord length, was 2,075,000.

Drag polars for a series of critical positive and negative flap deflection angles show a low airfoil drag coefficient of 0.006 for lift coefficients from 0.0 to 1.15. We compare this to similar plots for a current generation high-altitude, long-endurance aircraft with a conventional rotational flap. For a conventional flap, data indicates that positive flap deflections increase drag levels by 16% when the flap is deflected five degrees and by 25% when the flap is deflected ten degrees. This shows that the compliant trailing edge flap is aerodynamically superior to conventional rotational flaps.

This plot shows the coefficient of lift vs. the coefficient of drag for selected compliant trailing edge flap deflections. Note the large variation of lift production (CL = 0 to 1.1) with the drag coefficient at a constant low value of 0.006.

This plot shows the coefficient of lift vs. the coefficient of drag for a high-altitude, long-endurance airfoil with a conventional flap.