以流體模擬軟體為計算引擎之流固耦合力學分析系統開發

Abstract

隨著高效能運算技術的蓬勃發展，伺服器所搭載的處理器運算能力持續提升，伴隨而來的熱能散逸問題亦日益嚴峻。傳統風冷散熱技術已難以滿足高熱通量設備的冷卻需求。作為新興的散熱解決方案，浸沒式冷卻（Immersion Cooling）透過將伺服器元件完全浸泡於具電絕緣性的冷卻液中，有效提升熱交換效率、降低能耗與噪音，並延長設備壽命。此類冷卻技術背後牽涉到流體與固體之間複雜的交互作用，因此對流固耦合（Fluid-Structure Interaction, FSI）模擬的精確度與效率提出更高要求。流固耦合問題的應用不僅侷限於電子冷卻領域，亦廣泛存在於土木工程結構（如橋梁與離岸風機）、生物醫學系統與微機電元件（MEMS）等多種跨尺度工程中。儘管FSI模擬具有高度應用潛力，但傳統耦合方法在面對幾何複雜或物理行為劇烈變化的情況時，往往面臨網格劃分困難與計算成本過高等挑戰。 為解決此類問題，本研究致力於發展一套整合沉浸式有限元素法（Immersed Finite Element Method, IFEM）之流固耦合模擬系統。核心技術在於運用使用者自定義函式（User-Defined Function, UDF），以C語言撰寫嵌入至商用計算流體力學軟體AcuSolve之中，藉由二次開發的方式實現流場與固體間交互作用的耦合計算。該UDF模組具備高度可擴充性與靈活性，允許使用者根據模擬需求進行程式修改與功能擴充，成功將IFEM演算法實現在現有的商用求解器上。 本論文內容涵蓋模擬理論基礎、系統開發流程與UDF模組設計與驗證。論文架構如下：第一、二章回顧流固耦合的研究背景，並介紹有限元素法、超彈性材料與沉浸式有限元素法等相關理論；第三章說明UDF模組的開發流程與整合架構；第四章以所開發之UDF模組實作柔性固體與不同流場之交互作用，後半部則模擬振動箱內液體潑濺情境並進行分析；第五章則總結本研究成果並提出未來可能的延伸方向。

With the rapid advancement of high-performance computing technologies, the computing capabilities of server processors have significantly improved, resulting in increasingly severe heat dissipation challenges. Traditional air-cooling methods are no longer adequate to manage the high heat fluxes generated by such systems. As an emerging solution, immersion cooling submerges server components entirely in dielectric fluids, effectively enhancing heat transfer efficiency, reducing energy consumption and noise, and extending device lifespan. However, this innovative cooling approach involves complex fluid–solid interactions, thereby placing higher demands on the accuracy and robustness of fluid–structure interaction (FSI) simulations. FSI problems are not limited to electronic cooling; they are prevalent across a wide range of multiscale engineering applications, including civil infrastructure (e.g., bridges and offshore wind turbines), biomedical systems, and micro-electromechanical systems (MEMS). Despite its broad applicability, traditional FSI simulation methods often encounter challenges such as complex mesh generation and high computational costs, particularly when dealing with intricate geometries or strongly nonlinear physical behaviors. To overcome these limitations, this study proposes a simulation framework for FSI based on the Immersed Finite Element Method (IFEM). The core approach involves embedding User-Defined Functions (UDFs), written in C, into the commercial computational fluid dynamics (CFD) software AcuSolve. This secondary development enables direct coupling between the fluid and solid domains. The developed UDF module is highly modular and extensible, allowing users to adapt and expand the system to suit specific simulation requirements. As a result, the IFEM algorithm is effectively integrated into a commercial solver environment. This thesis presents the theoretical foundations, system implementation, and validation of the proposed framework. Chapters 1 and 2 review the background of FSI and introduce relevant theoretical concepts, including the finite element method, hyperelastic material models, and IFEM. Chapter 3 describes the development and integration process of the UDF module. Chapter 4 showcases the simulation of flexible structures interacting with various flow fields using the developed UDF, followed by an application to the simulation of liquid sloshing in a vibrating tank. Finally, Chapter 5 summarizes the key findings and suggests directions for future research.