TY - JOUR
T1 - Lift enhancement by a flapped trailing edge at low Reynolds number
T2 - A frequency response approach
AU - Shehata, Hisham M.
AU - Zakaria, Mohamed Y.
AU - Woolsey, Craig A.
AU - Hajj, Muhammad R.
N1 - Publisher Copyright:
© 2022 Elsevier Ltd
PY - 2022/4
Y1 - 2022/4
N2 - The capability of an oscillating trailing edge flap to enhance the lift generated by a rigid NACA-0012 airfoil at 2.1×104 Reynolds number is investigated. Experiments are performed at two angles of attack, namely α0=0∘ that represents a fully attached flow and α0=10∘ that represents a near-stall flow condition. The presented data and analysis cover sinusoidal oscillations of the flap at five reduced frequencies between k=0.02 and 0.12, and three oscillating amplitudes δA=5∘, 8° and 10° relative to the airfoil's angle of attack. Enhancement to the mean lift, lift-to-drag ratio, and unsteady lift dynamics are discussed. The validity of quasi-steady formulation of Leishman's model in predicting the lift is quantitatively assessed in light of the measurements. The unsteady lift dynamics generated by flap oscillations are modeled by constructing frequency response functions with the quasi-steady lift as the input and unsteady lift as the output. The experimentally determined gain variations are compared with analytically-derived gain functions. The effects of rate and amplitude of flap oscillations on lift cycle variations are examined using aerodynamic hysteresis response.
AB - The capability of an oscillating trailing edge flap to enhance the lift generated by a rigid NACA-0012 airfoil at 2.1×104 Reynolds number is investigated. Experiments are performed at two angles of attack, namely α0=0∘ that represents a fully attached flow and α0=10∘ that represents a near-stall flow condition. The presented data and analysis cover sinusoidal oscillations of the flap at five reduced frequencies between k=0.02 and 0.12, and three oscillating amplitudes δA=5∘, 8° and 10° relative to the airfoil's angle of attack. Enhancement to the mean lift, lift-to-drag ratio, and unsteady lift dynamics are discussed. The validity of quasi-steady formulation of Leishman's model in predicting the lift is quantitatively assessed in light of the measurements. The unsteady lift dynamics generated by flap oscillations are modeled by constructing frequency response functions with the quasi-steady lift as the input and unsteady lift as the output. The experimentally determined gain variations are compared with analytically-derived gain functions. The effects of rate and amplitude of flap oscillations on lift cycle variations are examined using aerodynamic hysteresis response.
KW - Flapped airfoil
KW - Frequency response
KW - Lift enhancement
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U2 - 10.1016/j.jfluidstructs.2022.103518
DO - 10.1016/j.jfluidstructs.2022.103518
M3 - Article
AN - SCOPUS:85124248213
SN - 0889-9746
VL - 110
JO - Journal of Fluids and Structures
JF - Journal of Fluids and Structures
M1 - 103518
ER -