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    题名: 定量與非定量拘限噴射流之量測
    其它题名: Measurements of Steady and Pulsatile of Confined Jet Flows
    作者: 盧博堅;賴和成
    贡献者: 淡江大學水資源及環境工程學系
    关键词: 噴射流;穩定流;脈動流場;雷諾切應力;紊流;Jet Flow;Steady Flow;Pulsatile Flow;Reynolds Shear Stress;Turbulent Flow
    日期: 2001-05-29
    上传时间: 2010-01-11 16:50:16 (UTC+8)
    出版者: 臺北縣:淡江大學
    摘要: 本實驗利用二維雷射測速儀(LDA)在拘限噴射流場中做不同軸向位置的量測,研究雷諾數介於22000至35000之定量流和不同脈動頻率脈動流流場之平均速度、主軸雷諾切應力、紊流尺度等之特性。實驗結果顯示,在定量流流場中,流場的形態並不會隨著雷諾的不同而改變。最大主軸雷諾切應力發生處的量值,為Sallamand Hwang(Biorheo1ogy 21,783-797[1984])提出的兩倍左右,顯示Sallam andHwang因未換算主軸切應力及實驗設備的限制,而使得所求得紅血球遭雷諾切應力的臨界值被低估了。在分析紊流尺度中發現流場中發生最小紊流尺度在各量測點的值大致相同,但在流速高之流場最小紊流尺度較流速低之流場為低。在不同脈動頻率的脈動流場中,利用平均相位法分離平均及擾動的成分。結果顯示,當平均速度增加時,主軸雷諾切應力亦增加。頻譜函數的結果亦顯示,亂流場的能量大小與平均速度的大小有直接的關連。在比較定量流流場與脈動流場中可發現,勢能流區的長度並不隨著脈動流場改變,且脈動流場峰值相位所產生主軸雷諾切應力無因次化量值大小較定量流場之量值小。
    In this study a simple pulsatile jet flow with two separate pulsefrequencies of 1.33 Hz and 2.0 Hz, which respectively correspond toheart rates of 80 and 120 beats per minute under physiologicalconditions, was used to measure the major principal Reynolds shearstress and turbulence length scales in the flow. Although the Reynoldsnumbers during the peak phases of the pulsatile flows, namely Re =55800 and 58400, are apparently larger than those of steady flows withRe = 22000, 28500, and 35000, the maximum major principal Reynoldsshear stress values measured during the peak phases of the pulsatileflows are significantly smaller. A value of 0.0065 was obtained inthis study, while 0.0093 was measured in the steady flows, differingby approximately 40%. On the other hand, the turbulence length scalesin both kinds of flow fields are relatively similar. This shows thatusing a steady jet flow to represent the peak phase of pulsatile flowwhile studying artificial prostheses could cause an overestimation ofthe turbulence stress values.
    關聯: 第三屆海峽兩岸航空太空學術研討會論文集,頁205-213
    显示于类别:[水資源及環境工程學系暨研究所] 會議論文

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