| 摘要: | 三維流固耦合行為是生活中處處可見的現象，小如浮球於水中的載浮載沉、風扇運轉推動空氣而造成的風場變化，大則受風力影響的摩天大樓搖擺或者橋梁振動、河川於急流下的沖刷行為，甚至如浮台式風力發電機同時受風和水作用，造成扇葉轉動與浮台浮動的多相流體與固體耦合現象，隨著市面上各式相關的分析軟體，與計算力學在此領域日漸成熟的發展，提供了工程師們許多工具可以處理流固耦合的複雜物理問題。
本研究以柔性體的流固耦合分析模式為基礎，開發另一剛性多面體的流固耦合程序，可依照使用者需求選擇剛體或可變形體的模組做模擬與分析，流體程式使用的是美國Los Alamos National Laborary所開發的軟體Truchas，求解三維不可壓縮流體之Navier-Stokes方程，以流體體積法(Volume of Fluid, VOF)追蹤各相流體運動行為，再利用移動固體法(Moving Solid Algorithm, MSA)計算固體移動後與各流體之互制行為。
固體部分將結構物離散成四面體元素組成，可使用向量式有限元素法(Vector Form Intrinsic Finite Element, VFIFE)進行柔性體的運動求解，以節點為參考計算受力的位移，並以逆向運動扣除元素的剛體運動求解變形及運動，剛性體程序則是以離散元素法(Discrete Element Method, DEM)來進行運動求解，以各離散四面體的慣性矩、慣性積，使用平行軸定理組合成整個結構體的慣性張量，找出主軸、主慣性矩後以塊體的質心做為參考點，分析受流體作用的合力與合力矩下之剛體運動分析。此一雙向的流固耦合分析程序，可模擬分析多相流體與固體的耦合行為，且程式碼為開放式的特性，完全可以依照需求來增加其分析模組，並可廣泛應用於工程上的流固耦合問題。
;The three-dimensional fluid-solid coupling behavior is a very common phenomenon in our life. It is as small as the floating and sinking of a floating ball in the water, and the wind field changes caused by the fan running to push the air, or as big as the swaying of skyscrapers or the vibration of bridges that are affected by wind, and the scouring behavior of rivers under the rapids, even if the floating wind turbine is affected by wind and water at the same time, the multiphase fluid and solid coupling phenomenon caused by the rotation of the fan blade and the floating of the floating platform, with various related analysis software on the market, and the maturing development of computational mechanics in this field, provides engineers with many tools to deal with the complex physics problem of fluid-structure interaction.
Based on the original fluid-structure coupling program of the flexible body, this paper develops another fluid-structure coupling program for a rigid body. According to the user′s needs, a rigid or a deformable body module can be selected for simulation and analysis. The fluid program uses Truchas which developed by Los Alamos National Laborary, solves the Navier-Stokes equations of three-dimensional incompressible fluids, uses the Volume of Fluid (VOF) method to track the fluid motion behavior of each phase, and then uses the Moving Solid Algorithm (MSA) method to calculate the interaction between the solid and each fluid after moving.
The solid is composed of discrete structures into tetrahedral elements, and the motion of the flexible body is solved using the Vector Form Intrinsic Finite Element (VFIFE) method. Deduct the rigid body motion of the elements to solves the deformation, and the rigid body program uses the Discrete Element Method (DEM) to solve the motion, using the inertia moment and inertia product of each discrete tetrahedron, the parallel axis theorem is used to accumulate and combine the inertia tensor of the entire structure, after find out the main axis and the main moment of inertia, then taken as the reference point of the mass center of the block to analyze the rigid body motion, which under the resultant force and resultant moment acted by the fluid. This two-way fluid-solid coupling analysis program can simulate and analyze the coupling behavior of multiphase fluids and solids, because the code is open-ended, so its analysis modules can be added according to requirements, and it can be widely used in engineering fluids-solid coupling problem. |
