A numerical analysis has been conducted to study the role of hindfoil initial pitch angle on aerodynamic performance of dragonfly hovering flight.The inclined oscillation of two elliptic airfoils with tandem arrangmen...A numerical analysis has been conducted to study the role of hindfoil initial pitch angle on aerodynamic performance of dragonfly hovering flight.The inclined oscillation of two elliptic airfoils with tandem arrangment at Re=157 is analysed using 2D numerical simulation.The pitch amplitude(α_(m))is kept constant for both foils and hindfoil initial pitch angle(α_(Oh))is varied from 15° to 75° for three different phase oscillations:φ=0°,90° and 180°.The results indicate,for α_(Oh)<45°,the lower α_(Oh) reduces total lift for all phase differences.It occurs due to the detrimental wake capture and downward dipole jet encountered by hindfoil during downstroke,resulting in less hindfoil C_(V).However,for α_(Oh)>45o,lift enhancement of up to 46% is observed with increase in α_(Oh) during φ=180°.Also,the higher thrust is obtained during lower α_(Oh) and it reduces with increase in α_(Oh).展开更多
文摘A numerical analysis has been conducted to study the role of hindfoil initial pitch angle on aerodynamic performance of dragonfly hovering flight.The inclined oscillation of two elliptic airfoils with tandem arrangment at Re=157 is analysed using 2D numerical simulation.The pitch amplitude(α_(m))is kept constant for both foils and hindfoil initial pitch angle(α_(Oh))is varied from 15° to 75° for three different phase oscillations:φ=0°,90° and 180°.The results indicate,for α_(Oh)<45°,the lower α_(Oh) reduces total lift for all phase differences.It occurs due to the detrimental wake capture and downward dipole jet encountered by hindfoil during downstroke,resulting in less hindfoil C_(V).However,for α_(Oh)>45o,lift enhancement of up to 46% is observed with increase in α_(Oh) during φ=180°.Also,the higher thrust is obtained during lower α_(Oh) and it reduces with increase in α_(Oh).
