Analysis of non-symmetrical flapping airfoils

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 num-ber,pitch amplitude and phase angle.In order to analyze thevariables more efficiently,the design of experiments usingthe response surface methodology is applied.Results showthat both the variables and shape of the airfoil have a pro-found effect on the lift,thrust,and efficiency.By using non-symmetrical airfoils,average lift coefficient as high as 2.23can be obtained.The average thrust coefficient and efficiencyalso reach high values of 2.53 and 0.61,respectively.The liftproduction is highly dependent on the airfoil’s shape whilethrust production is influenced more heavily by the variables.Efficiency falls somewhere in between.Two-factor interac-tions are found to exist among the variables.This shows thatit is not sufficient to analyze each variable individually.Vor-ticity diagrams are analyzed to explain the results obtained.Overall,the S 1020 airfoil is able to provide relatively goodefficiency and at the same time generate high thrust and liftforce.These results aid in the design of a better ornithopter’swing.