螺旋狀物體在剪切流中的運動行為; Motion of a screw in the shear flow

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题名:	螺旋狀物體在剪切流中的運動行為;Motion of a screw in the shear flow
作者:	趙家興;Chia-Hsin Chao
贡献者:	物理研究所
关键词:	螺旋狀;剪切流;shear flow;screw
日期:	2005-07-11
上传时间:	2009-09-22 10:56:36 (UTC+8)
出版者:	國立中央大學圖書館
摘要:	我們經由兩個不同的方法研究螺旋狀物體在剪切流中的運動行為，而在我們的實驗中我們用Couette flow system 來產生剪切流。螺旋狀物體在剪切流中以三種不同的方式擺放，且被限制只有垂直方向上可以自由移動。方式（ａ）：螺旋狀物體的長軸沿著Couette flow system 的徑向方向擺放。方式（ｂ）：螺旋狀物體的長軸沿著鉛直方向擺放。方式（ｃ）：螺旋狀物體的長軸沿著水流方向擺放。我們發現螺旋狀物體在剪切流中的受力是由其螺紋和剪切流的交互作用產生，且其運動行為和螺紋結構有關。作用在螺旋狀物體上的合力會隨著流速的增加而增加。左旋螺旋狀物體在剪切流中的運動型行為和右旋螺旋狀物體完全相反，所以此現象滿足鏡像對稱。 We use two different methods to study experimentally the motion of helical rods (screws) immersed in a shear flow produced by a Couette flow system. In our experiment, we observe three modes of the screw immersed in the shear flow and the screw is restricted to move only vertically (the vorticity direction). In mode (a), the lengthwise-axis of a screw is along the radial direction of the cylinder of the Couette flow system. In mode (b), the lengthwise-axis of a screw is vertical. In mode ( c ), the lengthwise-axis of a screw is parallel to the flow direction. We find that the motion of a screw result from the thread-shear flow interaction and some other effects, and it has a relation with the chiral structure of a screw. The resultant forces which act on the screw would increase while the velocity of flow increases. The motion of a left-hand screw immersed in the shear flow is opposite to the motion of a right-hand screw immersed in the shear flow, so all of the phenomenons of the screw ( right-hand and left-hand screw ) acted upon by a extra force would conform to the symmetry of a mirror image.
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