Enhancements to the FAST-MAC Circulation Control Model and Recent High-Reynolds Number Testing in the National Transonic Facility

Abstract

A second wind tunnel test of the FAST-MAC circulation control model was recently completed in the National Transonic Facility at the NASA Langley Research Center. The model was equipped with four onboard flow control valves allowing independent control of the circulation control plenums, which were directed over a 15% chord simple-hinged flap. The model was configured for low-speed high-lift testing with flap deflections of 30 and 60 degrees, along with the transonic cruise configuration with zero degree flap deflection. Testing was again conducted over a wide range of Mach numbers up to 0.88, and Reynolds numbers up to 30 million based on the mean chord. The first wind tunnel test had poor transonic force and moment data repeatability at mild cryogenic conditions due to inadequate thermal conditioning of the balance. The second test demonstrated that an improvement to the balance heating system significantly improved the transonic data repeatability, but also indicated further improvements are still needed. The low-speed highlift performance of the model was improved by testing various blowing slot heights, and the circulation control was again demonstrated to be effective in re-attaching the flow over the wing at off-design transonic conditions. A new tailored spanwise blowing technique was also demonstrated to be effective at transonic conditions with the benefit of reduced mass flow requirements.

Transonic Drag Reduction Through Trailing-Edge Blowing on the FAST-MAC Circulation Control Model

“…Analysis of wing surface pressure data from previous test entries for the two outboard pressure rows on the 0 • flap cruise configuration showed encouraging results, suggesting the potential for cruise drag reduction as a consequence of the blowing. 19 Similar results were seen in the wing surface pressures from this test entry. Figure 19 shows wing surface pressures for the most outboard pressure row at η = 0.8 at 15 and 30 million Reynolds number for M ∞ = 0.85 and M ∞ = 0.88.…”

“…Previous analysis of the wing surface pressures revealed that for attached flow conditions at M ∞ = 0.85, the circulation control blowing increased the lift and moved the shockwave aft on the wing, without changing the strength of the shockwave. 19 At the off-design conditions at M ∞ = 0.88, the blowing was effective in reattaching the shock-induced flow separation, moving the shockwave aft approximately 5% chord with no increase in shockwave strength. These encouraging results suggest that the circulation control blowing was effective in reducing the transonic drag on the configuration, however, this cannot be quantified until the thrust generated by the blowing slot is correctly removed from the force and moment balance data.…”

Yaw control of a flying-wing unmanned aerial vehicle based on reverse jet control

“…States has expanded the application of this circulation control technology from low speeds to subsonic speeds in their Fundamental Aerodynamics Subsonic/ Transonic-Modular Active Control. 18,19 In the subsonic range (M ¼ 0.85-0.88), circulation control can increase the maximum lift coefficient, effectively suppress the separation of flow on the flap, and delay the position of the shock wave. Shmilovich et al 20 found that active flow control used in conjunction with a simplified high-lift configuration can offer significant performance improvements for an airplane.…”

Low Speed Wind Tunnel Investigation of a Circulation Control Wing for Enhanced Lift

“…It is shown that flap angle and blowing momentum coefficient should increase for increased lift targets and good values for the flap length are found to be 0.25-0.30 of the airfoil chord. Recent research at NASA Langley Research Center (LaRC) 6,7 shows that a slot height to chord ratio of 0.0022 is more beneficial than larger slot height and can have the same performance with a 30% lower momentum coefficient of blowing. The FAST-MAC 6, 7 is tested at various flap deflections and low speed (M ∞ = 0.2) and high speed (M ∞ = 0.88) values to investigate the lift augmentation and the efficiency of drag reduction using CC.…”