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自由圓湍射流不穩(wěn)定性與界面擬序結(jié)構(gòu)研究
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國家自然科學(xué)基金項(xiàng)目(51176065),、江蘇省研究生科研創(chuàng)新基金項(xiàng)目(CXZZ11


Instability and Interfacial Coherent Structure of Free Round Turbulent Jet
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    摘要:

    采用兩相流動的大渦模擬對自由圓湍射流的流動不穩(wěn)定性及界面擬序結(jié)構(gòu)進(jìn)行了數(shù)值模擬。通過計(jì)算探討了射流液體的不穩(wěn)定性機(jī)制。研究了噴嘴入口速度及入口擾動對射流近場區(qū)的不穩(wěn)定性和渦結(jié)構(gòu)特性的影響。研究中,對雷諾數(shù)在10 000~80 000內(nèi)施加不同強(qiáng)度擾動后的射流流場進(jìn)行了系統(tǒng)的模擬計(jì)算,。結(jié)果表明:射流入口速度及外部擾動對射流的穩(wěn)定性有重要的作用,隨射流速度和擾動強(qiáng)度增加,其未擾液核長度下降,,表面波尺度減小,射流近場區(qū)產(chǎn)生更為豐富(長度尺度多,、渦旋強(qiáng)度范圍大)的特征渦旋結(jié)構(gòu),;從射流的時(shí)均流場看出,在相同雷諾數(shù)不同擾動強(qiáng)度(或相同擾動強(qiáng)度不同雷諾數(shù))下射流時(shí)均速度沿中心軸線衰減率基本類似,;隨雷諾數(shù)增加,,射流對周圍流體的正卷吸作用加強(qiáng),沿流向的徑向擴(kuò)散更為顯著,。

    Abstract:

    As a basic flow form, free round turbulent jet has been used in various industry fields such as water jet cutting,water cleaning, fuel spray, etc. To understand the development of jet and some of its underlying characteristics, it is crucial that the mechanism of jet instability should be recognized. A robust two-phase flow large eddy simulation (LES) algorithm was applied to predict the liquid instability and the coherent structure of free round turbulent jet. The main objective was to characterize the liquid instability mechanism without resorting stability analysis. Special attention was focused on how the instability and the eddy structure in the near field of round jet were affected by the imposed inlet velocity and disturbance. In this respect, the cases within the range of Re =10 000~ 80 000 at various disturbance intensities were tested. Results revealed that the velocity and disturbances played an important role in the stability of liquid jet. The unperturbed liquid core length and scale of surface wave were decreased, and a wide variety of vortexes were produced in the near field of jet with velocity and disturbance intensity increased. The decay rates of average velocity along the central axis of jet were similar under different disturbance intensities at the same Reynolds number (or different Reynolds numbers at the same disturbance intensity). The positive entrainment was enhanced and the radial spread of the jet along the streamwise became more significant with the Reynolds number increased.

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楊敏官,閆龍龍,王育立,龔辰,陸金剛.自由圓湍射流不穩(wěn)定性與界面擬序結(jié)構(gòu)研究[J].農(nóng)業(yè)機(jī)械學(xué)報(bào),2016,47(2):35-44. Yang Minguan, Yan Longlong, Wang Yuli, Gong Chen, Lu Jin’gang. Instability and Interfacial Coherent Structure of Free Round Turbulent Jet[J]. Transactions of the Chinese Society for Agricultural Machinery,2016,47(2):35-44.

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  • 收稿日期:2015-01-21
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  • 在線發(fā)布日期: 2016-02-25
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