非等溫紊流流場之微粒子傳遞過程

Particle transports in nonisothermal turbulence boundary layer flows

張茂雄(Mao-Hsiung Chang)

國立虎尾科技大學/工程學院/機械與機電工程研究所/碩士(2007年)

摘要

摘 要
本論文是在探討微粒子在非等溫紊流流場中的傳輸情形。本篇的數學模式是使用黏滯子層(sublayer)的觀念，再結合速度、溫度和濃度方程式來進行模擬。我們主要是改變微粒的釋放時間看出微粒在流場中的濃度分布與沉澱速度，在來分析出布朗擴散、turbophoretic、thermophoretic跟微粒的慣性對微粒的沉澱速度有何影響，進而延長液體與固體粒子在底層流動的時間。最後所分析出來的結果可藉由那些現象明顯的分出三個範圍，分別是 、 以及 ，透過這三個區間，可以清楚的了解到微粒在紊流中的傳輸情形。當 時，微粒主要是受到分子擴散的影響， 是受到turbophoretic的影響。當 時，是受到微粒的慣性的影響較大。

關鍵字 : 熱泳，紊流，黏滯子層，微粒

並列摘要

Abstract
Introducing coupled interactions between turbulence structures and dispersed phase into the fully developed-nonisothermal turbulence boundary layer flows has extended sublayer approach concept on liquid or solid particle transport. The comparable mechanisms dominating the instantaneous transport processes are transferred in the residence time of a single eddy, and then automatically considered on the average time domain of all eddy lifetimes by integrating the velocity, temperature, and concentration equations as a stochastic process with the aid of gamma density distribution.
An analytical approach derived from the time-averaged concentration distributions in fully developed-nonisothermal turbulence boundary flows serves as a basis for quantitative estimation of the particle deposition velocity during average growth/decay period of the viscous sublayer. The physical trends of the comparable effects between fluid turbulence and thermal intensity gradients on particle transport process are quantitatively revealed in some extent completing with the effects of mean axial pressure gradient, which becomes important for the deeper molecular penetration associate with low Reynolds number flows. The quantitative predictions are compared with previous models and experimental measurements to evaluate the feasibility of simply analytical approach on explaining the complex phenomena of the interaction between suspended particulate matter and carrier fluid turbulence in nonisothermal boundary layers. The theoretical simulation of particle transport can be further extended by including new forces in the analytical formulation through the equilibrium among acceleration terms.
Keywords：turbophoretic，thermophoretic，nonisothermal，particle

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