多孔隙介質內部流場之實驗分析

Experimental Analysis of Pore-Scale Liquid Flow inside a Porous Medium

黃永鳳(Michelle, Yung-Feng Huang)

指導教授 ： 陳榮河

共同指導教授 ： 卡艾瑋

國立臺灣大學/工學院/土木工程學研究所/博士(2008年)

https://doi.org/10.6342/NTU.2008.01540

摘要

多孔隙介質流場特性一直受到各個領域的重視，近年來由於數位影像設備及技術不斷進步，使得我們能夠以非侵入性方式研究孔隙中的流場特性。本研究試圖以折射率相同之多孔隙介質做為研究對象，且此多孔隙介質包含了直徑12 mm 及7 mm 之單一尺寸圓球顆粒堆積而成。孔隙中流場的追蹤是以一種能受到雷射光感應的示蹤劑作為追蹤流場的標的。本研究分別以人工判識及自動追蹤之方式取得二維流場於多孔隙介質中之速度資料。本實驗流場速度範圍橫跨雷諾數9 到雷諾數111。此外，為了瞭解孔隙中幾何構造如何影響流體速度，我們嘗試分析孔隙速度分布特性。其中，本研究採用一正規化之速度參考指標參數來描述此一特性，並且將該範圍之速度繪於流場中以了解其分布位置關係。此外，本研究尚分析徑向速度分布及孔隙位置與固體邊界距離之關係。最後，我們使用一常用於分析紊流系統之統計方式－機率密度函數 (Probabilty density function, pdf) 來分析流場之速度分布情形。此外，本研究亦針對人工及自動方式判識結果進行整體之統計分析及誤差分析。希望藉由這一系列定性及定量分析結果讓我們更加了解多孔隙介質中流體的特性。

關鍵字

多孔隙介質 ； 折射率 ； 粒子影像追蹤 ； 機率密度函數 ； 流場分析

並列摘要

A non-intrusive technique based on refractive index matching is used to study flow in porous media. The porous media considered in this study are random packed beds composed of 7 mm and 12 mm diameter spheres. Fluid velocities in a constant head permeameter set-up are tracked by seeding tracer particles illuminated by laser light and observed by a CCD camera. Two different velocity tracking methods are applied to obtain the velocity data. The first method involves manual tracking of colorized multiple exposure frames. The other is a fully automatic particle tracking velocimetry (PTV) method. The errors of different methods are evaluated by analyzing velocity distribution errors and checking discharge discrepancies. Velocity field results are compared for different Reynolds numbers going from Re=10 to Re=100. As the Reynolds number increases by one order of magnitude, vortex wake flow and swirl are observed in the stagnation zones. Moreover, four normalized velocity ranges are examined to understand the major features of the flow fields. Radial distributions of velocities and a possible dependence on distance away from solid boundaries are also examined. Finally, the probability density function (pdf) is used to compare data from different Reynolds numbers and tracking methods.

並列關鍵字

porous media ； refractive index matched ； PTV ； probability density function

參考文獻

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