方形溝漕中兩層流體於入口段共擠流動特性分析

Flow Characteristic Analysis for Two-Layered Fluids in the Entry section of a Rectangular Channel

連國智(Guo-Jhih Lian)

指導教授 ： 蘇淵源

國立臺北科技大學/工程學院/化學工程研究所/碩士(2008年)

https://doi.org/10.6841/NTUT.2008.00307

摘要

本研究是以高黏彈性流體(柏格流體)及黏度相近的牛頓流體分別與24.8%鹽水進行配對，並行流進寬厚比28:1之方形溝槽中，探討界面波的形成機制及行為，並利用高速攝影機搭配影像擷取與軟體去決定界面產生波動的介穩線。實驗顯示入口段的擠壓會造成界面波的產生，而我們亦以擾動漩渦理論及擾動能量理論來解釋此形成的機制。接著以高階頻譜分析及pule shift技巧來計算界面波的波速及群速。且由bicoherence spectral證實主要波和各簡諧波之間有能量傳遞的行為。最後我們更證明入口段界面波的成長是屬非線性可描述之系統。

關鍵字

柏格流體 ； 界面波

並列摘要

A highly viscoelastic fluid (Berger’s fluid) or a Newtonian fluid with equivalent viscosity is respectively paired with 24.8% saline, flowing parallel into a channel with a width-thickness ratio of 28:1, to study the formation mechanism and behavior of the interfacial waves. A high speed camera with image capture and software was used to determine the neutral stability line of interfacial wave generations. The experiment revealed the interfacial wave originates at the exit of co-extrusion die. The disturbance vortex theory and the disturbance energy theory are used to explain the mechanism of interfacial wave growth. Higher order cross spectral and pulse shift techniques is implemented to determine the wave speed and group velocity of interfacial waves. Energy transfer between leading harmonic and overtones is confirmed by bi-coherence spectral. Finally we demonstrate that the growth of interfacial wave near the die exit can not be described by the linear stability analysis.

並列關鍵字

Boger fluid ； interfacial waves ； cross spectral ； bicohernece spectral

參考文獻

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