以離散元素法電腦模擬探討顆粒體在不同置入物儲槽中的傳輸性質與內部性質;Numerical Study on Transport and Internal Properties of Granular Materials in Cylindrical Silos with Different Inserts Using Discrete Element Modelling

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Title:	以離散元素法電腦模擬探討顆粒體在不同置入物儲槽中的傳輸性質與內部性質;Numerical Study on Transport and Internal Properties of Granular Materials in Cylindrical Silos with Different Inserts Using Discrete Element Modelling
Authors:	郭庭君;Kuo, Ting-Chun
Contributors:	機械工程學系
Keywords:	三維儲槽;顆粒物質;置入物;離散元素模擬;傳輸性質;內部性質;3D silo;granular materials;insert;discrete element modelling;transport property;internal physical property
Date:	2020-07-30
Issue Date:	2020-09-02 19:08:26 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究採用離散元素法(Discrete Element Method, DEM)模擬顆粒體在六種置入物儲槽中循環排放時的流動與力學行為，此六種置入物分別為無置入物，倒圓錐型，圓片型，圓錐中空型，圓柱中空型，及儲槽中空型置入物，並提出切片法模型模擬顆粒體在儲槽中的流動行為，進一步分析置入物對儲槽中顆粒流傳輸性質與內部性質的影響，研究結果顯示：(1) 倒圓錐型、圓片型與圓錐中空型三種置入物儲槽顆粒體的垂直速度與徑向速度差異較小且較為均勻分佈，粒子溫度呈現更均勻分佈，滯留時間較為集中，質量流率皆較低，有助於改善儲槽中顆粒體的流動行為；(2) 六種置入物儲槽的粒子體積佔有率峰值皆約為0.62，在靠近儲槽邊壁或置入物邊壁區域的粒子體積佔有率較小，此外靠近中心處呈現更小的粒子體積佔有率；(3) 當六種置入物儲槽顆粒流態由均勻穩定轉換成不均勻時，呈現極大的正向應力。垂直應力分佈中可以發現由接觸力產生的架橋效應，倒圓錐型與圓片型置入物儲槽造成正向應力三個分量的峰值提高且範圍更廣，而儲槽中空型置入物儲槽在正向應力三個分量皆呈現最大值；(4) 六種置入物儲槽的Von Mises應力分佈與垂直應力分佈最為接近，這說明儲槽不論是否安裝置入物，儲槽內部應力的傳遞主要由垂直應力控制；(5)六種置入物儲槽中在傾斜邊壁與置入物上方區域受阻擋作用影響，均導致不均勻與不穩定顆粒流進而引起較強烈的異向性，以致應力比大於1.0，甚至高達2.4。;The purpose of this study is to investigate the flow and mechanical behavior of granular materials in cylindrical silos with six different inserts by using Discrete Element Method (DEM). These inserts include conical insert, disk insert, BINSERT, hollow cylinder insert and hollow silo insert. To substantially reduce computer time, a slice method is proposed to simulate the flow behavior of granular materials in the silo. Furthermore, the effect of insert geometry on transport properties and internal physical properties of the granular flow in the silo is analyzed. Key findings are highlighted as follow: (1) In the silos with conical insert, disk insert, and BINSERT, the granular flow exhibits more uniform vertical and radial velocity profiles. The granular temperature is evenly distributed, and the residence time is also relatively concentrated, the mass flow rate shows smaller values. (2) The peak value of solid fraction in the silos with six kinds of insert is approximately 0.62. The solid fraction shows smaller values near the silo walls and inserts. Furthermore, the solid fraction near the center shows the smallest values. (3) When the granular flow is transformed from stability to non-uniform, the granular assembly experiences a great normal stress. The spatial distribution of vertical stress demonstrates the arching phenomena caused by the contact force. The peak values of normal stress increase and its spatial distribution becomes wider in the silo with conical insert and disk insert. However, the normal stress for the silo with hollow silo insert shows large values. (4) Von Mises stress distribution in the silos shows very similar pattern to the vertical stress. This indicates that the stress state in the silos is dominated by the vertical stress. (5) The granular flow in the silos subject to obstruction is uneven and unstable and shows strong anisotropy, resulting in a stress ratio greater than 1.0, even up to 2.4.
Appears in Collections:	[Graduate Institute of Mechanical Engineering] Electronic Thesis & Dissertation

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