Frequency Response of Aerodynamic Load Control through Mini-tabs

TY - GEN

T1 - Frequency Response of Aerodynamic Load Control through Mini-tabs

AU - Heathcote, Daniel

AU - Gursul, Ismet

AU - Cleaver, David

PY - 2017/1/11

Y1 - 2017/1/11

N2 - Load control is the reduction of extreme aerodynamic forces to enable lighter, more efficient aircraft. Current load control technologies are limited to low frequency disturbances. In this paper the mini-tab, a small, span-wise tab placed on the airfoil upper surface, is investigated as a high frequency alternative through periodic oscillations to identify its unsteady aerodynamic transfer function. Force measurements were conducted on a NACA0012 airfoil at a Reynolds number of 6.6x105 with a deployable mini-tab located at xf/c = 0.85, with actuation performed at reduced frequencies, k ≤ 0.79. The force measurements indicate that the mini-tab has a decreasing effect on lift reduction with increasing actuation frequency. This trend is comparable to Theodorsen’s function, based on the change in circulation. For α = 0°, the normalized peak-to-peak lift reduction decreased from 1 for steady state deployment to around 0.6 at k = 0.79. In addition, a phase lag exists between the mini-tab deployment and the aerodynamic response which increased with actuation reduced frequency, k. However, the measured phase lag is substantially larger than Theodorsen’s prediction. Increasing the angle of attack, α reduced the mini-tab’s effect on lift while increasing the phase angle when comparing equal k values. Particle Image Velocimetry measurements indicate that the delay and reduction in effectiveness of periodic deployment is due to the presence and growth of the separated region behind the mini-tab. Overall, the mini-tab was found to be an effective, dynamic lift reduction device with the separated region behind the mini-tab key to the amplitude and phase delay of lift response.

AB - Load control is the reduction of extreme aerodynamic forces to enable lighter, more efficient aircraft. Current load control technologies are limited to low frequency disturbances. In this paper the mini-tab, a small, span-wise tab placed on the airfoil upper surface, is investigated as a high frequency alternative through periodic oscillations to identify its unsteady aerodynamic transfer function. Force measurements were conducted on a NACA0012 airfoil at a Reynolds number of 6.6x105 with a deployable mini-tab located at xf/c = 0.85, with actuation performed at reduced frequencies, k ≤ 0.79. The force measurements indicate that the mini-tab has a decreasing effect on lift reduction with increasing actuation frequency. This trend is comparable to Theodorsen’s function, based on the change in circulation. For α = 0°, the normalized peak-to-peak lift reduction decreased from 1 for steady state deployment to around 0.6 at k = 0.79. In addition, a phase lag exists between the mini-tab deployment and the aerodynamic response which increased with actuation reduced frequency, k. However, the measured phase lag is substantially larger than Theodorsen’s prediction. Increasing the angle of attack, α reduced the mini-tab’s effect on lift while increasing the phase angle when comparing equal k values. Particle Image Velocimetry measurements indicate that the delay and reduction in effectiveness of periodic deployment is due to the presence and growth of the separated region behind the mini-tab. Overall, the mini-tab was found to be an effective, dynamic lift reduction device with the separated region behind the mini-tab key to the amplitude and phase delay of lift response.

UR - http://dx.doi.org/10.2514/6.2017-0947

U2 - 10.2514/6.2017-0947

DO - 10.2514/6.2017-0947

M3 - Conference contribution

SN - 9781624104473

BT - 55th AIAA Aerospace Sciences Meeting, 2017

PB - American Institute of Aeronautics and Astronautics

ER -