Abstract
Simulations have been done to assess the lift, thrust and propulsive efficiency of different types of non-symmetrical airfoils under different flapping configurations. The variables involved are reduced frequency, Strouhal number, pitch amplitude and phase angle. In order to analyze the variables more efficiently, the design of experiments using the response surface methodology is applied. Results show that both the variables and shape of the airfoil have a profound effect on the lift, thrust, and efficiency. By using non-symmetrical airfoils, average lift coefficient as high as 2.23 can be obtained. The average thrust coefficient and efficiency also reach high values of 2.53 and 0.61, respectively. The lift production is highly dependent on the airfoil’s shape while thrust production is influenced more heavily by the variables. Efficiency falls somewhere in between. Two-factor interactions are found to exist among the variables. This shows that it is not sufficient to analyze each variable individually. Vorticity diagrams are analyzed to explain the results obtained. Overall, the S1020 airfoil is able to provide relatively good efficiency and at the same time generate high thrust and lift force. These results aid in the design of a better ornithopter’s wing.
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Abbreviations
- c :
-
airfoil chord
- C d :
-
drag coefficient
- C l :
-
lift coefficient
- \({\bar {C}_l }\) :
-
average lift coefficient
- C p :
-
pressure coefficient
- C t :
-
thrust coefficient
- \({\bar {C}_t }\) :
-
average thrust coefficient
- f :
-
frequency, Hz
- h :
-
instantaneous heaving position
- \({h'_0 }\) :
-
heaving amplitude
- h 0 :
-
heaving amplitude, non-dimensionalized by airfoil chord
- k :
-
reduced frequency f c/U ∞
- L :
-
lift force
- M :
-
moment created by the lift and drag forces at the pitching axis
- p :
-
pressure
- P :
-
power input
- \({\bar {P}}\) :
-
average power input
- p s :
-
statistical value calculated by Minitab to determine if the variable or interaction is significant
- Re :
-
Reynolds number
- St :
-
Strouhal number \({fh'_0/U_\infty }\)
- t :
-
non-dimensionalized time
- t 0 :
-
time when flapping starts
- T :
-
thrust force
- u b :
-
grid velocity
- u i :
-
Cartesian velocity components
- U ∞ :
-
freestream velocity
- x i :
-
Cartesian coordinates
- θ :
-
instantaneous pitch angle, in degrees
- \({\phi }\) :
-
phase difference between pitching and heaving, in degrees
- θ 0 :
-
pitch amplitude, in degrees
- η :
-
propulsive efficiency
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Tay, W.B., Lim, K.B. Analysis of non-symmetrical flapping airfoils. Acta Mech Sin 25, 433–450 (2009). https://doi.org/10.1007/s10409-009-0259-1
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DOI: https://doi.org/10.1007/s10409-009-0259-1