Experimental Study On The Aerodynamic Characteristics Of Liriodendron Leaves

In this paper,the aerodynamic characteristics of liriodendron leaves were studied by experimental methods.To find the main factors which affect the critical wind speed of liriodendron leaves;the change of leaves' resistance coefficient with the increase of wind load,the effect of vibration on the resistance coefficient;study the vibration frequency of the leaves and show the flow field distribution of the longitudinal and cross section of the tail end of the leaves.Experimental methods include high-speed camera recording,wind tunnel balance test,particle image related vibration measure vibration,hot wire anemometry and particle image velocimetry display flow.?1?Status analysis: Through analysis the real liriodendron leaves' area,the ratio of leaf length and width,blade length to diameter,we found that the critical Reynolds number Re is a function of leaf area S and leaves' length to width ratio L1/B3.By changing one of the influencing factors: petiole length,petiole thickness and size of leaf area,for artificial liriodendron leaves the critical velocity V is a function of leaf area S and petiole thickness d and petiole length's reciprocal.?2?Force analysis: The drag coefficient of real liriodendron and artificial liriodendron leaves decreased with the increase of Reynolds number and finally approaches between 0.1-0.3,leaf area,leaf thickness and petiole length are important factors of influencing the resistance coefficient for artificial liriodendron leaves.?3?Vibration analysis: With the wind speed increases,the vibration frequency of the artificial liriodendron leaves in three directions of the UVW first increased and then decreased,in the last they trend consistent.?4?The display of tail flow fieid: When the wind speed is less than V₁,wake of real leaves and the artificial leaves have a stable vortex shedding but the frequency of the loss is very low.When the wind speed reaches V₁,the frequency of the vortex shedding frequency increases and appears resonance frequency,and the weak is not obvious when the leaves are in a conical shape.With the change of leaves' states,the cross section flow field of the weak from no whirlpool,two whirlpools are gradually formed,with leaves vibration vortex shedding phenomenon,and two vortex size decreases gradually with the increase of wind speed.