It is necessary to examine the aerodynamic behaviour of leaves in wind in order to understand wind-induced tree disasters. The effect of the wind deflection angle on the aerodynamic characteristics of leaves remains relatively unexplored. Thus, the reconfiguration, vibration and wake characteristics of the Betula platyphylla Sukaczev leaves at various wind deflection angles and vegetative Cauchy numbers were investigated in a wind tunnel. Wind deflection angle (θ) is defined as the angle between the wind direction and the normal vector of the lamina, and a vegetative Cauchy number characterises the reconfiguration of an elastic structure under flow and is defined as the ratio of the product of the dynamic pressure and the third power of the slenderness ratio to the elasticity modulus. The results showed that at the different cases with an increase of Cauchy number, all the leaves mainly experience three states, a static bending of the laminas, and an opening and closing vibration of the laminas on left and right sides and a reconfiguration of the leaf. Except for the leaves with θ = 0, the leaves with θ = π/6, π/3 and π/2 also experience torsional motion. Four critical Cauchy numbers were defined corresponding to the four reconfigurations and vibration states. The mean critical Cauchy numbers for the torsional motion of the leaves were at θ = π/6, π/3 and π/2 this decreased with the increasing θ. The reconfigured mean Cauchy numbers of leaves for θ = π/6, π/3 and π/2 were significantly larger than those in θ = 0. Furthermore, compared with the case for θ = 0, the cases with θ = π/6, π/3 and π/2 proved to be disadvantageous for the reduction of vortex-induced vibrations through reconfiguration.

为了了解风引起的树木灾害，有必要检查树叶在风中的空气动力学行为。风偏角对叶片空气动力学特性的影响仍然相对未探索。因此，在风洞中研究了不同风偏角和植物柯西数下白桦树叶的重构、振动和尾流特性。风偏角 ( θ) 定义为风向与层板法向量之间的夹角，植物柯西数表征流动下弹性结构的重构，并定义为动态压力与叶片的三次幂的乘积之比长细比与弹性模量之比。结果表明，在不同情况下，随着柯西数的增加，所有叶片主要经历叶片静态弯曲、左右叶片开合振动和叶片重构三种状态。 . 除了θ  = 0 的叶子，θ的叶子 = π/6、π/3 和 π/2 也经历扭转运动。对应于四种重构和振动状态定义了四个临界柯西数。叶片扭转运动的平均临界柯西数为θ  = π/6、π/3 和 π/2，这随着θ的增加而减小。θ  = π/6、π/3 和 π/2的重新配置的平均叶柯西数显着大于θ  = 0 的情况。 此外，与θ  = 0 的情况相比，θ  = π/6 的情况, π/3 和 π/2 被证明不利于通过重新配置减少涡激振动。