Experiments on Active Drag Reduction on a Complex Outer Wing Model

Wing Tip Drag Reduction at Nominal Take-Off Mach Number: An Approach to Local Active Flow Control with a Highly Robust Actuator System

“…Figure 5 shows the drag coefficient curves with and without flow control for experiments conducted at M = 0.1 in the two respective wind tunnels. Note, that the actuator system for all curves shown in this figure is the valve driven version from [18]. Despite the differences in wind tunnel size the resulting drag coefficient curves for the uncontrolled flow agree remarkably well with respect to absolute (normalized) values and stall behavior.…”

“…Namely, the comparison of results across wind tunnels and the influence of the test Mach number. Experiments on a similar geometry with only slightly reduced geometric complexity, reported in [18], were conducted earlier in TUB's GroWiKa 4 wind tunnel facility. In this test facility the maximum Mach number is limited to M = 0.13.…”

“…In this test facility the maximum Mach number is limited to M = 0.13. The main difference in the experimental setup, however, is the ratio of model size and wind tunnel cross section, which is A re f A w/t,GroWiKa ≈ 17% for the results of [18] and A re f A w/t,DNW−NWB ≈ 6% for the DNW-NWB results. Figure 5 shows the drag coefficient curves with and without flow control for experiments conducted at M = 0.1 in the two respective wind tunnels.…”

“…2) is located between y/b = 40% and y/b = 75% of the model's span. Its design is based on experience from numerical and experimental studies on a similar geometry [17,18]. A total of 28 rectangular slots are integrated parallel to the leading edge at x/c re f ≈ 5% on the suction-side surface.…”

“…The jet densities for different mass flow rates were established in bench-top experiments. A more detailed description of the c µ calculation is found in [18]. When multiple segments were active, the c µ value quoted is the sum of the values for each active segment.…”