以隨機走步方式探討黏滯效應對噴流發展之影響

Investigations on the Development of Viscous Plane Jet by Random Walk Method

王健彰(Chien-Chang Wang) ； 許掙強(Cheng-Chiang Hsu) ； 林怡劭(Yi-Shao Lin) ； 洪振益(Chen-I Hung)

《航空太空及民航學刊.系列B》 40卷1期 (2008/04) Pp. 11-19

https://doi.org/10.6124/JAAA.200804_40(1).02

摘要

本文採用渦流法模擬二維平面噴流之流場並加入隨機走步的方式以探討黏滯效應對噴流發展之影響。模擬的流場有R(下? e)=10^1，10^2，10^3及10^4等情況。模擬結果發現R(下? e)=10^1之流場，由於黏滯擴散效應相對較強足以主導整體流場，使得流場所展現的特性，如流場煙線、相似性、頻譜等皆與其他雷諾數流場情況大相逕庭。此外，模擬結果與已有的實驗數據基本一致，顯示採用隨機走步式之渦流法模擬噴流流場是可行的。由模擬之結果可看出渦元煙線與流場煙線在低雷諾數有下明顯之差異，故將實驗煙流視察之結果視為渦量分佈及渦結構是需十分謹慎的。模擬結果顯示中心速度變化特性及勢流錐附近流場之主導頻率，隨雷諾數增加而變化率越來越小，即當雷諾數高至某一程度流場渦結構之發展與雷諾數之相關性將愈來愈低。

關鍵字

隨機走步 ； 渦流法 ； 平面噴流

並列摘要

The evolutions of viscous plane jet are simulated by using the vortex method with random walk to investigate the influence of the viscous effects. Various Reynolds numbers, R(subscript e)=10^1, 10^2, 10^3 and 10^4, are applied for investigating the evolution of the flow field. Results display that the flow field of R(subscript e)=10^1 different from others because the viscous diffusion is sufficiently dominant over convection.
In addition, the computational results agree with those of available literatures. Thus the simulation of the plane jet by using vortex method incorporated with random walk is quite reasonable and acceptable. A great difference exists between vortex streaklines and flow streaklines at low Reynolds numbers. It means that using flow streaklines to identify vortex structures at low Reynolds numbers is unsuitable. At high Reynolds numbers, flow properties are little altered by the change of Reynolds numbers.

並列關鍵字

Random walk ； Vortex method ； Plane jet