離散元素模擬之平行策略

Parallel DEM Simulation Strategy

林立欣(Li-Shin Lin)

指導教授 ： 謝尚賢

國立臺灣大學/工學院/土木工程學研究所/碩士(2005年)

https://doi.org/10.6342/NTU.2005.01583

摘要

有鑑於離散元素法的模擬隨元素數量增加伴隨而來的龐大計算時間，本研究提出了離散元素法的平行策略，而此平行策略係建立在一個能勝任多種元素形狀與多種元素間力學機制的離散元素模擬的離散元素程式架構，名為VEDO架構(VErsatile Discrete Objects framework)，其設計上將元素模型描述與力學機制演算法兩者抽離，僅在執行期間求解碰撞力學行為時將兩者作動態連結。本研究詳述了平行策略中的各項細節，包括工作量如何分配、處理器間溝通的時機與訊息內容等。
本研究建置出的平行離散元素模擬程式已應用在自充填混凝土砂漿的流動行為模擬。砂漿元素為由混凝土中細骨材、水、粉體共同構成的膠狀溶液，欲作自充填混凝土的流動模擬，可取其離散元素模型為粗骨材元素(代表粗骨材)與砂漿元素的二相組合。然而，砂漿元素為以離散顆粒模擬漿液的虛擬元素，顆粒參數與配比參數的關聯必須先經由砂漿流動試驗數據與砂漿流動模擬結果來建立。由於三維砂漿模擬需要很多的元素數目以致於計算量龐大，本研究建置出的平行離散元素程式藉由多個處理器的分工以減少執行時間，以使三維砂漿模擬能實現。

關鍵字

離散元素法 ； 平行計算

並列摘要

In order to reduce the computation time involved with DEM (Discrete Element Method) simulation with large numer of elements, this research proposes a parallel strategy for a DEM simulation program framework, named VEDO (VErsatile Discrete Objects framework). In the design of VEDO framework, element model description and inter-element mechanism algorithm are separated, so VEDO framework is capable of performing simulations having elements with various shapes and various inter-element mechanisms. The complete detail of the proposed parallel strategy, including how to distribute the work-load, when and by what content will the collaborating processors communicate, is presented in this thesis.
For conducting a flow simulation of Self-Compacting Concrete (SCC) using DEM, the element model can be a two-phase combination of arrgegate and mortar particles. The former simulates the real-world coarse aggregates, and the latter simulates the mortar solution composed of fine aggregates, water and cement. Because the mortar particles are “virtual” in the sense that they do not correspond directly to discrete mortar objects in the real world, the relationships between mechanical parameters of the mortar particles and mix proportion must be established in advance from both the results of mortar flow simulation and mortar flow tests. However, mortar flow simulations require huge computation time. Therefore, a parallel DEM program has also been developed in this research to make feasible the three-dimensional flow simulation of motar solution.

並列關鍵字

parallel computing ； discrete element method ； DEM

參考文獻

陳詩華(2003)，“離散元素分析之後處理圖形程式系統開發與應用”， 碩士論文，國立臺灣大學土木研究所，台北

Yang, C. T., Hsieh S. H. and Lin L. S. (2004) “Design of an XML-based Markup Language for Discrete Object Simulations”, Bulletin of the College of Engineering, N.T.U., No. 92, February 2004, 121–135.

Bonet, J., and Peraire, J. (1991). “An Alternating Digital Tree (ADT) Algorithm for 3D Geometric Searching and Intersection Problems”, International Journal for Numerical Methods in Engineering, 31, 1-17.

Dowding, C. H., Dmytryshyn, O., and Belytschko, T. B. (1999). “Parallel Processing for a Discrete Element Program,” Computers and Geotechnics, 25(4), 281-285.

Giani G. P., Giacomini A., Migliazza M., and Segalini A. (2001). “Design of Rockfall Restraining Nets From a Discrete Element Modelling,” Rock Mechanics and Rock Engineering, 34(2), 99-118.