力元理論應用於紊流模式

The applications of Force Element on Turbulence Model

陳泰元(Tai-Yuan Chen)

指導教授 ： 張建成

共同指導教授 ： 郭志禹(Chih-Yu Kuo)

國立臺灣大學/工學院/應用力學研究所/碩士(2013年)

https://doi.org/10.6342/NTU.2013.10882

摘要

本論文主要討論均勻入流流經物體之流場分析，並且探討流場結構與物體受力之關係。一般在討論物體的受力情形，其藉由計算物體表面的表面摩擦力以及表面壓力，並且利用表面積分計算出物體的升、阻力之情形，但此現象並不能描述流場中流體的物理結構對物體受力的影響，而本文使用Chang(1992)力元理論將分解出不可壓縮流流場中，各流體元素對物體所產生的受力貢獻。
此研究將力元理論引用至紊流模式，因此將輔助勢流與平均雷諾方程式作內積並取體積分，並且將導出升、阻力係數與表面摩擦項、體積渦度項與雷諾應力項之關係，藉由此觀點將可觀察出流場物理性質與物體受力之關係，並可藉此方法來判斷這些流場的型態，對於物體個貢獻是造成正貢獻升、阻力係數或是負貢獻升、阻力係數，則可利用此分析、設計，控制流場流體特性進而達到有利的流場應用。
本文的主題主要針對環繞NACA0015機翼且雷諾數為 的升、阻力之情形，利用兩種不同的紊流模式(1) 紊流模式與(2)雷諾應力模式來進行模擬，取得紊流場的的物理特性，並嵌入使用者自訂方程將計算力元分析。同時探討在不同攻角下以及不同的紊流強度下，在不同的情況下流體元素各別對物體的貢獻的大小及其影響。

關鍵字

力元理論 ； 紊流模式 ； 環繞機翼流場

並列摘要

The thesis analyzed flow field that uniform inflow flow through the objects, and discussed flow field structure and the total force that imposed on the objects. In general, using surface friction and surface pressure calculated force distribution of the objects. However, we made surface integral and calculated that the nature of flow field produced force, using Chang(1992) force element. The fluid property was analyzed and made force element composition.
The research employed force element and turbulence model. Besides, potential flow let Reynolds average equation inner product, and took volume integral, and produced lift or drag coefficient. The lift or drag coefficient was relate to surface friction, volume vorticity and Reynolds stress. So could use this method, got the nature of flow field and force distribution of objects. By this behavior, could judge flow field property that provided positive value or negative value for the objects. Besides, could change shape, got new flow field property and effectively provided positive lift.
The turbulence models, (1) k-epsilon turbulence model, (2) Reynolds model, were used to simulate lift or drag coefficient with NACA0015 airfoil and Reynolds number of . We got turbulence flow field property and used Ansys Fluent to compute the basic flow information and combining flow information with force element. Besides, we also made different angle of attack or turbulence intensity. Observing the fluid element influence and contribute to drag or lift coefficient.

並列關鍵字

Force element ； Turbulence Model ； Flow around the wing

參考文獻

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