| Summary: | 碩士 === 逢甲大學 === 機械與電腦輔助工程學系 === 103 === This paper record the falling process of floral cone which used the ratio of petal and torus 2:1, 2.5:1, and 3:1 to clarify the impact of the air resistance acted on the rotating free-fall object.
Results show that both the axial drag and the circumferential drag acted on rotating free-fall object, the axial drag combined by the axial components of the shear forces and pressure forces on the surface of the objects the circumferential drag comes from the shear force,the circumferential drag the hich generated torque to the axis of the floral cone cause the floral cone rotating. Using the floral cone with larger cone angles and moment of inertia to extend the time of the falling process because the cone rotated slowly and the terminal velocity is very small. The analysis of momentum reveals that the axial drag of the floral cone with the same number of the petal and the ratio of area is smaller than circumferential drag. With bigger cone angle, the circumferential drag will increase more than axial drag. As the ratio of area getting bigger, there is no increasing of the axial drag and circumferential drag.
According to the analysis of energy, the initial potential energy of the floral cone in the free-fall process transfer to linear kinetic energy, rotating energy, axial dissipated energy and the circumferential dissipated energy. When the floral cone with same number of petal and the ratio of area falls to ground, the potential energy, linear kinetic energy, rotating energy, axial dissipated energy and the circumferential dissipated energy will increase. As long as increasing the cone angle, linear kinetic energy will decrease, rotating energy will increase at beginning then start to decrease, axial dissipated energy will decrease a little bit and circumferential dissipated energy will be bigger. It concludes that the circumferential drag caused by rotating motion will increase the air drag effectively during the process of free-fall.
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