射流卷吸边界层内相干结构的实验研究
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摘要
在轴对称水射流实验台上,采用单帧长曝光图像法,测量了出口Reynolds数在1849～2509范围内的卷吸边界层内流场结构。发现在流向距离L=2D～3.5D,径向距离H=D～1.25D的区域内,流场中吞噬作用和侵蚀作用两种卷吸模式交替出现。分析得到,当Re>1915时,吞噬作用所占的比例随着Re的增大而增大,当Re>2311之后,Reynolds数对该结构发生概率的影响降低;通过快速傅里叶变换得到该相干结构发生的频率在10～19Hz之间;吞噬作用发生的同时在流场中观测到一些特殊涡结构。同时采用运动单帧长曝光图像法对射流流场进行拉格朗日法观测,发现射流流场中的涡结构一般存在于湍流与非湍流界面附近。
On the axis-symmetric water jet test bench, the flow field structure in the entrainment boundary layer with the Reynolds number in the range of 1849-2509 was measured by the single-frame long exposure image method. It is found that engulfing and nibbling entrainment model occur intermittently with time, in the region of L=2D-3.5D streamwise and H=D-1.25D radial direction. It concludes from analyzing that the occurrence probability of engulfing increases with Reynolds number when Re>1915, the influence of Reynolds number on the occurrence probability of this structure decreases when Re>2311. The occurrence frequency of this coherent structure obtained by fast Fourier transform is between 10 Hz and 19 Hz. Special vortex structures were observed in the flow field during the occurrence of engulfing. The jet flow field are measured using moving single frame long exposure image method in Lagrangian coordinate system, and it is found that the vortex structure generally existed near the interface of turbulent regions and non-turbulent regions.
On the axis-symmetric water jet test bench, the flow field structure in the entrainment boundary layer with the Reynolds number in the range of 1849-2509 was measured by the single-frame long exposure image method. It is found that engulfing and nibbling entrainment model occur intermittently with time, in the region of L=2D-3.5D streamwise and H=D-1.25D radial direction. It concludes from analyzing that the occurrence probability of engulfing increases with Reynolds number when Re>1915, the influence of Reynolds number on the occurrence probability of this structure decreases when Re>2311. The occurrence frequency of this coherent structure obtained by fast Fourier transform is between 10 Hz and 19 Hz. Special vortex structures were observed in the flow field during the occurrence of engulfing. The jet flow field are measured using moving single frame long exposure image method in Lagrangian coordinate system, and it is found that the vortex structure generally existed near the interface of turbulent regions and non-turbulent regions.
引文
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[26]Lu C,Liu Y,Niu S.Examination of turbulent entrainment-mixing mechanisms using a combined approach[J].Journal of Geophysical Research Atmospheres,2011,116:D20207(1)-D20207(12).
[27]Silva C B D,JoséC F P.Invariants of the velocity-gradient,rateof-strain,and rate-of-rotation tensors across the turbulent/nonturbulent interface in jets[J].Physics of Fluids,2008,20(5):055101(1)-055101(18).
[28]周骛,朱赠好,蔡小舒.射流卷吸微米级结构的图像可视化研究[J].工程热物理学报,2014,35(6):1123-1126.Zhou W,Zhu Z H,Cai X S.Image visualization of microstructures in the entrainment by jet flow[J].Journal of Engineering Thermophysics,2014,35(6):1123-1126.
[29]陈晶丽,李琛,蔡小舒,等.流动多参数场的单帧图像法测量方法研究[J].实验流体力学,2015,29(6):67-73.Chen J L,Li C,Cai X S,et al.Research on the single frame imaging method for measuring multi-parameter fields in flow field[J].Journal of Experiments in Fluid Mechanics,2015,29(6):67-73.
[30]曲宁宁,蔡小舒,周骛,等.运动单帧图像法湍流边界层相干结构的实验测量[J].化工学报,2017,68(11):4088-4094.Qu N N,Cai X S,Zhou W,et al.Experimental measurement of coherent structures of turbulent boundary layer by motion single frame imaging method[J].CIESC Journal,2017,68(11):4088-4094.
[2]Davies P O A L,Fisher M J,Barratt M J.The characteristics of the turbulence in the mixing region of a round jet[J].Journal of Fluid Mechanics,1963,15(3):337-367.
[3]董志勇.射流力学[M].北京:科学出版社,2005:4-31.Dong Z Y.Jet Mechanics[M].Beijing:Science Press,2005:4-31.
[4]耿铁,李德群,周华民,等.冲击射流及其强化换热的研究进展[J].机械设计与制造,2006,(6):154-156.Geng T,Li D Q,Zhou H M,et al.Development of the studies about heat transfer with impinging jets[J].Machinery Design&Manufacture,2006,(6):154-156.
[5]Pope S B.Turbulent flows[J].Turbulent Flows,2000,12(11):96-181.
[6]Rodrigo R T,JoséS D,Diogo C,et al.Lagrangian statistics across the turbulent-nonturbulent interface in a turbulent plane jet[J].Physical Review E,2013,88(4):043001(1)-043001(12).
[7]赵清华,全学军.轴对称射流研究进展[J].重庆理工大学学报,2003,17(4):38-41.Zhao Q H,Quan X J.Progress in axisymmetric jet study[J].Journal of Chongqing Institute of Technology,2003,17(4):38-41.
[8]林建忠,林江.轴对称射流场涡结构的离散涡段方法研究[J].力学季刊,1999,1999(2):148-155.Lin J Z,Lin J.On the vortex structures in axisymmetric turbulent jet flows[J].Chinese Quarterly of Mechanics,1992,1999(2):148-155.
[9]余常昭,李春华.圆形断面自由湍动射流卷吸的实验研究[J].实验流体力学,1996,1996(1):31-38.Yu C Z,Li C H.Experimental study on the entrainment for turbulent round jets[J].Journal of Experiments in Fluid Mechanics,1996,1996(1):31-38.
[10]黄真理,李玉梁,余常昭.平面激光诱导荧光技术测量横流中射流浓度场的研究[J].水利学报,1994,(11):1-7.Huang Z L,Li Y L,Yu C Z.Measurement of jet concentration field by planar laser induced fluorescence technique[J].Journal of Hydraulic Engineering,1994,(11):1-7.
[11]黄真理.紊动射流的分维测量[J].科学通报,1994,39(6):567-567.Huang Z L.Fractal dimension measurement of turbulent jet flow[J].Chinese Science Bulletin,1994,39(6):567-567.
[12]刁永发,何伯述,许晋源,等.四角燃烧器射流向火侧相干结构涡的研究[J].中国电机工程学报,2003,23(3):150-155.Diao Y F,He B S,Xu J Y,et al.Coherent structure vortices on the fire-facing side of four burner jets[J].Proceedings of the CSEE,2003,23(3):150-155.
[13]刁永发,何伯述,许晋源,等.大型电站锅炉燃烧器区向火侧剪切大涡的尺度及其旋转速度[J].热能动力工程,2003,18(1):20-22.Diao Y F,He B S,Xu J Y,et al.The scale and rotation speed of share large vortices on the fire-facing side of the burner zone of a large power station[J].Journal of Engineering for Thermal Energy and Power,2003,18(1):20-22.
[14]Westerweel J,Hofmann T,Fukushima C,et al.The turbulent/nonturbulent interface at the outer boundary of a self-similar turbulent jet[J].Experiments in Fluids,2002,33(6):873-878.
[15]Gan L,Nickels T B.An experimental study of turbulent vortex rings during their early development[J].Journal of Fluid Mechanics,2010,649(6):467-496.
[16]Gan L.Detection of passive scalar interface directly from PIVparticle images in inhomogeneous turbulent flows[J].Flow Turbulence&Combustion,2016,97(1):141-170.
[17]Gan L,Maffioli A.The size and lifetime of organized eddies in an on-solid-body rotating turbulence experiment[J].European Journal of Mechanics-B/Fluids,2019,74:41-49.
[18]Wolf M,Lüthi B,Holzner M,et al.A Lagrangian,small-scale investigation of turbulent entrainment in an axisymmetric jet[J].Journal of Physics Conference Series,2011:767-772.
[19]Markus H,Liberzon A,Nikitin N,et al.A Lagrangian investigation of the small-scale features of turbulent entrainment through particle tracking and direct numerical simulation[J].Journal of Fluid Mechanics,2008,598(7):465-475.
[20]Yadav H,Agrawal A,Srivastava A.Mixing and entrainment characteristics of a pulse jet[J].International Journal of Heat and Fluid Flow,2016,61:749-761.
[21]Glezer A.An experimental study of a turbulent vortex ring[J].Journal of Fluid Mechanics,1981,211(211):243-283.
[22]Silva C B D,Taveira R R,Borrell G.Characteristics of the turbulent/nonturbulent interface in boundary layers,jets and shear-free turbulence[J].Journal of Physics:Conference Series,2014:012015(1)-012015(19).
[23]Silva C B D,Taveira R R.The thickness of the turbulent/nonturbulent interface is equal to the radius of the large vorticity structures near the edge of the shear layer[J].Physics of Fluids,2010,22(12):121702(1)-121702(4).
[24]Diogo A J,Taveira R R,Silva C B D.Eulerian and Lagrangian statistics across the turbulent/non-turbulent interface in turbulent jets[C]//Meeting of the APS Division of Fluid Dynamics.American Physical Society,2012.
[25]Silva C B D,Reis R J N D,Pereira J C F.The intense vorticity structures near the turbulent/non-turbulent interface in a jet[J].Journal of Fluid Mechanics,2011,685(7):165-190.
[26]Lu C,Liu Y,Niu S.Examination of turbulent entrainment-mixing mechanisms using a combined approach[J].Journal of Geophysical Research Atmospheres,2011,116:D20207(1)-D20207(12).
[27]Silva C B D,JoséC F P.Invariants of the velocity-gradient,rateof-strain,and rate-of-rotation tensors across the turbulent/nonturbulent interface in jets[J].Physics of Fluids,2008,20(5):055101(1)-055101(18).
[28]周骛,朱赠好,蔡小舒.射流卷吸微米级结构的图像可视化研究[J].工程热物理学报,2014,35(6):1123-1126.Zhou W,Zhu Z H,Cai X S.Image visualization of microstructures in the entrainment by jet flow[J].Journal of Engineering Thermophysics,2014,35(6):1123-1126.
[29]陈晶丽,李琛,蔡小舒,等.流动多参数场的单帧图像法测量方法研究[J].实验流体力学,2015,29(6):67-73.Chen J L,Li C,Cai X S,et al.Research on the single frame imaging method for measuring multi-parameter fields in flow field[J].Journal of Experiments in Fluid Mechanics,2015,29(6):67-73.
[30]曲宁宁,蔡小舒,周骛,等.运动单帧图像法湍流边界层相干结构的实验测量[J].化工学报,2017,68(11):4088-4094.Qu N N,Cai X S,Zhou W,et al.Experimental measurement of coherent structures of turbulent boundary layer by motion single frame imaging method[J].CIESC Journal,2017,68(11):4088-4094.