中文摘要 隨著電腦運算能力的進步,現在已經可以模擬三維型式的顆粒運動,更真實的反應其運動。以往在模擬大量顆粒時,常因接觸判斷耗費許多時間,故本文以Cundall提出之分離元素法(DEM)所發展的三維顆粒理論為基礎,導入加速搜尋的觀念,簡化接觸判斷以增進程式效率。 再者,以往對於時間步長及接觸彈簧勁度範圍的選擇並無規範,本文針對一般常用的設定,藉由一系列的模擬測試,最終歸納出合理可行的選取參數並整理成圖表,未來使用者可依此圖表選取個人所需之參數。在模擬碰撞方面,本文亦提出臨界速度的概念,在模擬成果合理可信的前提下求出圓球運動速度的上限值,避免錯誤的模擬成果。
Abstract With the progress of computing ability, so far the three-dimensional motion of particles has been simulated more accurately. It often spent lots of time on simulating huge amount of particles due to contact detection. In this paper, a three-dimensional ball theory based on Discrete Element Method(DEM) original proposed by Cundall(1971) was developed, the concept of accelerated search was introduced, and the contact detection was simplified to increase the efficiency of programs. Furthermore, because there was no standard about time step and the range of contact spring stiffness in the past, the purpose of this paper is to set up a relation to the selection of parameters and organized into a chart by a series of simulation tests. Users can select the required parameters individually according to the chart in the future. Under the premise of reasonable and credible simulations, this paper also discuss the concept of critical velocity to derive the upper limit of ball velocity on normal contact in order to avoid errors.