三維多相流體與柔性固體耦合互制分析; Interaction Analyses of Three Dimensional Multiphase Fluids and Flexible Solids

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Title:	三維多相流體與柔性固體耦合互制分析;Interaction Analyses of Three Dimensional Multiphase Fluids and Flexible Solids
Authors:	黃致榮;Huang,Chih-Jung
Contributors:	土木工程學系
Keywords:	流固耦合分析;三維多相流;多體力學;結構破壞多重災害;地震;土石流;橋墩沖刷;Fluid-structure interaction analysis;Three-dimensional multiphase flow;Multi-mechanics;Structure Multi-hazard;Earthquake;debris flow;Pier Scour
Date:	2013-07-02
Issue Date:	2013-08-22 11:37:55 (UTC+8)
Publisher:	國立中央大學
Abstract:	三維流體與結構動力互制行為內涵豐富而複雜的物理現象，可應用於相關之設計及分析工作之中，因而長久以來為工程師所關注，而計算力學正是一種有效的方法提供工程師獲得此類問題更多細部訊息。因此本論文提出了一種新開發之流固耦合分析程序，可應用於研究離散可變形固體與多相流體的運動分析，流體程式是使用Los Alamos National Laboratory (LANL)所開發之軟體Truchas，固體運動則是使用向量式有限元素法(Vector Form Intrinsic Finite Element, VFIFE)加以求解。此一雙向流固耦合移動固體法，運動固體表面壓力是透過求解Navier-Stokes方程，利用流體體積法Volume-Of-Fluid (VOF)追?自由液面的運動，改良投影法完成壓力和速度場去耦合動作，最後利用雙向移動固體法做為VFIFE模型及VOF模型間的橋梁。隨著這種新開發的移動固體法，分析過程不再需要預定固體運動之軌跡。向量式有限元素法將固體及結構之運動視為一群由獨立節點所組成，整體結構的大變形及破壞行為模擬是由每個承受外力及內力之節點加以描述。相較於傳統非線性結構分析，向量式有限元素法可免去求解繁複的迭代問題及偏微分方程式，關鍵架構如下：（1）點值描述（Point Value Description, PVD），（2）途徑單元(Path Element) 及（3）移動參考構架(Convected Material Frame, CMF）。利用上述功能，向量式有限元素法可輕易且適切地使用力控制及位移控制進行物體運動由連續至不連續之狀態分析，所以此新發展之流固耦合方法將可應用於地震、泥石流、風、浮木、洪水引起之複合式災害及結構損壞之診斷評估問題。 Three dimensional fluid-structure dynamic interaction behaviors contain fruitful and complex physical phenomena and are interested to engineers for their design and analysis works. Computational mechanics is an effective way to assist engineers obtaining more detail information for this type of problem. This dissertation presents a newly developed fluid-solid interaction analysis algorithm. This algorithm can be used to investigate the motions of discrete deformable bodies in multi-phase viscous fluid. The CFD analysis in this computation algorithm uses the Truchas developed by the Los Alamos National Laboratory (LANL) and the motions of the solids are computed by a algorithm developed based on the vector form intrinsic finite element (VFIFE) method. A two-way coupled moving solid algorithm is developed. The motions of solids are based on the surface pressure obtained from solving the Navier-Stokes equations. The free-surface kinematic is tracked by the volume-of-fluid (VOF) method. The modified projection method is used to decouple and solve the pressure and velocity field. The two-way coupled moving solid method is developed to bridge the VFIFE model and VOF model. With this newly developed moving-solid method, the trajectory of the solid motion is no longer needed to be prescribed. The VFIFE method analyzes the motion of the solids and structures by modeling the individual object as a group of representative finite particles. The motion of each particle subjected to external and internal forces is used to simulate the large displacements and failures of the whole structure. The VFIFE method based on the intrinsic theories of mechanics avoids the difficulties such as the iterative and perturbation procedures in solving partial differential equations in the traditional nonlinear structural analyses. The key concepts in the analysis of the VFIFE method are: (1) the point value description (PVD), (2) the path element, and (3) the convected material frame (CMF). With these features, the VFIFE method can analyze the motion of a body from continuous states to discontinuous states with load control or displacement control easily and adaptively. Hence, the multi-hazard and failure analyses of infrastructures under the excitations of earthquake, debris flow, wind and flood can be conducted by this newly proposed computational fluid-structure interaction analysis method.
Appears in Collections:	[Graduate Institute of Civil Engineering] Electronic Thesis & Dissertation

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