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標題: | 無網格數值方法於泛牛頓流體之熱流模擬 Meshless Methods for Generalized Newtonian Fluid Flow and Heat Transfer |
作者: | Shu-Ping Hu 胡淑評 |
指導教授: | 楊德良 |
關鍵字: | 無網格法,類比方程式法,徑基底函數法,熱傳,奈維爾-史托克方程式,泛牛頓流體,黏滯加熱。, Meshless,meshless analog equation method,radial basis functions,heat transfer,Navier-Stokes equations,generalized Newtonian fluid,viscous heating., |
出版年 : | 2010 |
學位: | 博士 |
摘要: | 本論文中將非牛頓流體簡化為泛牛頓流體,其黏度以Power law model 及 Cross model 描述,進而以無網格數值法模擬及分析其穩態及暫態之流動與熱傳現象。本論文所採用的無網格數值法都是將數值解以基底函數的累加表示,不需要網格的建置且不需數值積分。所採用的無網格數值法可分為兩類: 1.全域式 2. 區域式。全域式的無網格法有: 類比方程式法 (MAEM),基本解-特解法(MFS-MPS),特解法 (MPS),主要用於模擬穩態溫度場與速度場。區域式的無網格法為:區域式徑基底函數法 (LRBF),用於求解二維及三維時變性溫度-速度耦合問題。全域式的無網格法因所有計算點的權重都考慮使其有高的精確度;而區域式的無網格法因只考慮附近點的權重會使得精確度略為下降。但也因為全域式法考量所有點的權重導致計算矩陣為滿矩陣,若應用於時變性問題時,將耗用相當多的計算資源,且不利於將計算點數加大。故時變性問題,我們採用區域式無網格法,僅考慮附近點對本身的影響,有效降低記憶體需求量與計算時間,使得無網格數值法可成功推廣於模擬真實流場問題。再者,無網格數值法可隨意內插任意位置點的物理量及其導數,這對計算模擬提供相當大的幫助。文中所使用的無網格數值結果均與解析解或文獻中的結果比較,證明所使用的無網格法之正確性與高效率,且說明所提出之無網格數值法乃一值得研究發展的高效率計算方法。 The present research aims to develop a meshless numerical model for the simulation of non-Newtonian fluid flows and heat transfer problems. The non-Newtonian fluid is simplified as a generalized Newtonian fluid (GNF). The viscosity of the GNF is descried by Power law model and Cross model. The numerical solution by a meshless method is expressed by a linear combination of radial basis functions (RBFs). No mesh generation and numerical integral are needed. The meshless numerical methods concerned in this dissertation consist of two types: 1. global method; and 2. local method. Global methods are the meshless analog equation method (MAEM), the combination of method of fundamental solutions and method of particular solutions (MFS-MPS), the method of particular solution (MPS). The adopted local method is the local radial basis function (LRBF) scheme. In this dissertation, the global methods are used to solve the steady equations of temperature and velocity; the local method is applied to solving unsteady 2D and 3D unsteady temperate-velocity coupling equations. The global meshless scheme has high accuracy due to the full consideration of weighting of global supporting nodes, but the global supporting nodes induce a highly ill-conditioned full matrix. It is time-consuming to solve the dense matrix equations. The global meshless methods are not easy to be extended to time dependent problems. Therefore, the local meshless method is introduced for solving unsteady problems. The LRBF scheme approximates the numerical solutions by a linear combination of supporting nodes in every local region. The memory requirement and the cost of CPU time are reduced. Moreover, mesh methods only provide the solution at mesh points, while the meshless method can interpolate the physical value and its derivatives everywhere with high accuracy. The advantages of the meshless methods are very useful for industrial applications. The numerical results by the present methods are compared with the results in the literature. The comparisons show the accuracy of the meshless methods and also demonstrate that the meshless methods are worth developing. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/46924 |
全文授權: | 有償授權 |
顯示於系所單位: | 土木工程學系 |
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