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    Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/1248


    Title: 蛋形顆粒與多面體塊體之數值模擬;Numerical Simulation for Granular Assemblies Composed of Egg-shaped Particles and Polyhedron Blocks
    Authors: 陳昭雄;Chao-hsiung Chen
    Contributors: 土木工程研究所
    Keywords: 分離元素法;卵型顆粒;多面形塊體;接觸判斷;巴西堅果效應;Brazil nut effect;polyhedron block;egg-shaped particle;contact detection;discrete element method
    Date: 2008-12-10
    Issue Date: 2009-09-18 17:24:42 (UTC+8)
    Publisher: 國立中央大學圖書館
    Abstract: 自然界中許多材料是離散體,例如砂土和岩石,擁有許多不同的形狀。對於數值模擬分析上,以分離元素法來模擬較為合適。前人研究混合型剛體顆粒系統之數值模擬與卵形顆粒介質運動之數值模擬,本研究將兩者研究之成果結合並修改。並且加上可以排列顆粒在空中之前處理程式,使顆粒在模擬開始前即可以隨機排列且不會重疊,後處理則修改前人使用MATLAB寫出之動畫程式,使其可以畫出多面形塊體。 本研究主要將卵形顆粒和多面塊體接觸判斷完成,卵形顆粒與橢球顆粒一樣係由四圓弧逼近法所形成,然而橢球顆粒只是卵形顆粒的特例形狀。將卵形顆粒加入到混合型剛體顆粒系統可以讓其更為廣義。卵形顆粒的球面與弧面分別可能會和多面形塊體的(1) 頂點(2) 稜線(3) 面接觸,然而卵形顆粒和多面形塊體稜線或面接觸時,程式可能會誤判在範圍之外接觸,於是必須加入界內外判斷。在程式完成後,以不同的算例來驗證程式的正確性,包含: (1) 卵形顆粒拋體運動驗證 (2) 多面形剛體與卵形顆粒碰撞的線動量守恆 (3) 摩擦力驗證。在確認程式無誤之後,使用程式模擬巴西堅果效應,在尺寸不同的混合顆粒中,經過震動後,體積較大的顆粒會往上運動,在自然界也會發生這種狀況,例如土石流發生時,大的石頭會在上層,小的石頭會在下層。 Many materials in the world are discrete material, such as sand and rocks which always get irregular shape. It is proper to discrete element method for numerical simulation. The main idea of this thesis is combination the achievement of “Numerical Simulation for Granular Assemblies Egg-shaped Particle” and ” Numerical Simulation for Granular Assemblies with Mixed 3D Rigid Body ”. In addition, add the pre-processor code to arrange the position of the particles and prevent the particle overlap when the code assigns the position of the particle. In the post-processor part, the animate code is expanded the polyhedron block. Actually, the main idea of this research is accomplishment of the contact detection between the egg-shaped particle and polyhedron block. The egg-shaped particle is formed by four-circle approximation method so as to form the ellipsoid. The ellipsoid only is the special case of the egg-shaped particle. Thus the “Numerical Simulation for Granular Assemblies with Mixed 3D Rigid Body” is more generalized. The egg-shaped particle would contact with the polyhedral block in these three ways: (1) ball- vertex (2) curve-vertex (3) ball-edge (4) curve-edge (5) ball-plane (6) curve-plane. When the egg-shaped particle contact with the edge of the polyhedron block or the plane of the polyhedron block, it could detect the out range of the polyhedron block as contact. So it must be to add the mechanism to detect the contact point inside or outside. After finishing the code, there are three examples to test the correction of the code. (1) projectile of the egg-shaped particle (2) the linear momentum equilibrium of the collision of polyhedron block and the egg-shaped particle (3) friction test. This research simulates the Brazil nut effect. After shaking the particle assemblies , the bigger particle would motion to the upper of the particle assemblies. Many examples occur the Brazil nut effect in the world. For example, the mud slide is. The bigger rocks would appear upper portion of the rocks.
    Appears in Collections:[土木工程研究所] 博碩士論文

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