透過您的圖書館登入
IP:44.201.97.0
  • Theses

多球體在黏性流的動態運動模擬

Simulation of Multi-particle Dynamic Motion in Viscous Fluid

Advisor : 陳俊杉

Abstracts


本研究為以電腦數值方法,進行多球體顆粒於黏性流中的三維運動模擬。由整合許多高效率的演算法,包括以晶格波茲曼法(Lattice Boltzmann Method, LBM)求解不可壓縮黏性流場,以離散元素法(Discrete Element Method, DEM)求解固體顆粒的移動以及接觸行為,並且以沉浸邊界法(Immersed Boundary Method, IBM)取代傳統邊界問題的方式,求解固體跟液體的交互作用行為。而在整合系統的實作過程,應用了平行演算法,增加大尺度問題的計算效率。一般常見的IBM為在固定的流場格點上,以Lagrangian座標的積分點描述固體邊界的分佈,並以插分計算的方式,把Lagragian座標積分點上的資訊,影響到周圍Eulerian流場格點。在大量固體邊界的情況下,頻繁的內插動作動作會使得計算效率低落。因此我們於IBM實作上採用了以體積分數函數(volume fraction function)的方式描述固體邊界,簡化了在固體邊界描述上複雜內插計算。本研究以模擬單顆粒子在黏性流中沉降、兩顆粒子的DKT(drafting、kissing、tumbling)行為,以及應用於土壤力學中的滲流砂湧問題。而在滲流造成的砂湧現象模擬中,根據土壤力學的土壤有效應力概念以及砂湧現象的解釋,證實了觀察到模擬成果中砂湧的發生,並以模擬過程所得到的資訊,試圖說明砂湧現象的成因。我們發現到砂湧現象的發生,並非僅來自於滲流水壓的正向推移造成顆粒試體抬升,其中包括孔隙水在孔隙之間迴流,對顆粒造成的扭矩,增加顆粒的角速度,減少顆粒之間的摩擦阻力以及使顆粒產生垂直於正向力的升力,使顆粒之間的交互作用力更容易減少,破壞顆粒的排列結構,進而發生砂湧。

Parallel abstracts


This research focuses on three-dimensional simulation of the motion of multiple solid particles in viscous flow. By integrating discrete element method, lattice Boltzmann method and immersed boundary method to solve the interaction between solid particle and viscous fluid. To improve the efficiency of solving large scale model, this integrating scheme is implemented with parallel computing. The traditional immersed boundary method creates many integrating point to describe the solid boundary. And the bodies forces come from boundary are interpolated to the neighbor fluid nodes. However, the frequent interpolation will spend very much computing time. This research implements volume fraction function immersed boundary method. Volume fraction function is a more efficiency way to describe solid boundary effect in the fluid. This research simulates single particle sediment in a box, two particles’ DKT behavior and quick condition for particles. The simulating quick condition phenomenon is verified by the definition from soil mechanics. And we try to explain the mechanism which causes the quick condition for particles. The quick condition is not only cause by the normal stress in the direction of pressure difference. Institute fluid makes circulating flows in the spaces between particles. This flow cause torques to counter the friction forces between particles. The counter behavior will break the structure of particles’ configuration and makes quick condition occurs easier.

References


[15] VEDO. Department of Civil Engineering at National Taiwan University. .
[3] Yang, F.-L., Chang, W. T., Huang, Y. T., Hsieh, S. H. and Chen, C. S. (2010), “A new contact model for discrete element simulation of dry or immersed granular avalanches,” 
[1] Shamy, U. E. and Zeghal, M. (2005), “Coupled Continuum-Discrete Model for Saturated Granular Soils,” J. Eng. Mech., 131, pp. 413–426.
[2] Cundall, P.A. (1971), “A computer model for simulating progressive large scale movements in blocky rock systems,” Proceedings of Symposium of International Society of Rock Mechanics. Nancy, France. Vol. 1, Paper II-8.
[7] Peskin, C.S. (1982), “The fluid dynamics of heart valves: experimental, theoretical, and computational methods,” Ann. Rev. Fluid Mech., 14, pp. 235-259.

Cited by


溫鈺翔(2014)。可分享土木領域實驗資料、模擬結果與模型的社群平台設計〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2014.01901
莊益彰(2012)。固液二相流計算平台開發與應用〔碩士論文,國立臺灣大學〕。華藝線上圖書館。https://doi.org/10.6342/NTU.2012.10252
方緯宸(2013)。以COMSOL Multiphysics模擬氣懸微粒於靜電集塵式細胞株暴露系統中之運動軌跡〔碩士論文,國立中央大學〕。華藝線上圖書館。https://www.airitilibrary.com/Article/Detail?DocID=U0031-0605201417532014

Read-around