Abstract：
The diversity in butterfly morphology has attracted many people around the world since ancient times. Despite morphological diversity, the wing and body kinematics of butterflies have several common features. In the present study, we constructed a bottom-up butterfly model, whose morphology and kinematics are simplified while preserving the important features of butterflies. The present bottom-up butterfly model is composed of two trapezoidal wings and a rod-shaped body with a thorax and abdomen. Its wings are flapped downward in the downstroke and backward in the upstroke by changing the geometric angle of attack (AOA). The geometric AOA is determined by the thorax-pitch and wing-pitch angles. The thorax-pitch angle is actively controlled by abdominal undulation, and the wing-pitch angle is passively determined because of a rotary spring representing the basalar and subalar muscles connecting the wings and thorax. We investigated the effectiveness of abdominal undulation for thorax-pitch control and how wing-pitch flexibility affects aerodynamic-force generation and thorax-pitch control, through numerical simulations using the immersed boundary-lattice Boltzmann method. As a result, the thorax-pitch angle perfectly follows the desired angle through abdominal undulation. In addition, there is an optimal wing-pitch flexibility that maximizes the flying speed in both the forward and upward directions, but the effect of wing-pitch flexibility on thorax-pitch control is not significant. Finally, we compared the flight behavior of the present bottom-up butterfly model with that of an actual butterfly. It was found that the present model does not reproduce reasonable body kinematics but can provide reasonable aerodynamics in butterfly flights.
摘要：
自古以来，蝴蝶形态的多样性就吸引了世界各地的许多人。尽管形态多样性，蝴蝶的机翼和身体运动学有几个共同的特征。在本研究中,我们构建了一个自下而上的butterfiy模型，它的形态和运动学是简单的fied，同时保留了蝴蝶的重要特征。当前的自下而上的蝴蝶模型由两个梯形机翼和一个带有胸部和腹部的杆状身体组成。通过改变几何攻角，它的机翼在下冲程中向下滑动，在上冲程中向后滑动。几何攻角由胸俯仰角和翼俯仰角确定。胸部俯仰角由腹部起伏积极控制，机翼俯仰角是被动确定的，因为旋转弹簧代表连接机翼和胸部的基底和下肌。我们研究了腹部起伏对胸部俯仰控制的影响，以及机翼俯仰的灵活性如何影响空气动力的产生和胸部俯仰控制，通过使用浸没边界晶格Boltzmann方法进行数值模拟。因此,由于腹部起伏，胸部俯仰角完全遵循所需的角度。此外,有一个最佳的机翼间距的灵活性，最大限度地提高在向前和向上方向上的速度，但是机翼-螺距-反射率对胸腔-螺距控制的影响并不显著。最后,我们比较了当前自下而上的蝴蝶fiy模型与实际的蝴蝶fiy的行为。结果发现，目前的模型不能重现合理的车身运动学，但可以提供合理的空气动力学。
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