淹没射流流场演化过程研究
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摘要
射流在工程领域具有非常广泛的用途,为得到射流流场的演化过程,深入研究射流的运动机理,采用大涡模拟方法(LES)对淹没射流紊动流场进行数值模拟,采用有限体积法(FVM)和PISO算法进行方程离散和数值计算,得到了淹没射流的瞬态流场。分析压力场的演化过程发现,压力场等值线呈一簇簇同心圆,沿射流轴线方向和垂直射流轴线方向圆心高压和圆心低压交错分布;随着射流的进行,同心圆随射流下移并伴有变形、分裂、融合等现象。在淹没射流区和冲击射流区前部分,同心圆圆心的压力上下波动并呈上升趋势;在附壁射流区,同心圆圆心的压力较为平稳,进行较低频率、小幅度的波动。分析速度场的演化过程发现,在射流的进行中,射流主体左右摆动,轴线处存在高速流体团脱落现象。射流主体上固定点的速度和压力大小有显著的负相关关系。分析涡量场的演化过程发现,两个涡量束呈分段化中间大两端小的"藕"形分布,并随时间进行随机摆动。通过涡量场与压力场的对比看出,涡旋的摆动造成了射流主体的摆动,涡旋的存在导致了压力场圆心低压和圆心高压交错分布。淹没射流流场具有很强的紊动性和随机性,对射流流场演化过程和水力特性内在关系的研究得出了一些规律性的结论,但如射流摆动的定量分析等仍有许多内容有待研究。
Jets are widely used in various hydraulic applications.To observe the evolution of flow field and to investigate the mechanism of a submerged jet,Large eddy Simulations(LES) was utilized to simulate flow field with finite volume method(FVM) for discretization and PISO method for pressure calculation.From the analysis of the evolution of pressure field,the contours of pressure presented to be a cluster of concentric circles,and high pressure and low pressure circles appeared alternately along the jet axis.During the jet impinging,the concentric circles were moving along the jet with deformation,further splitting and merging.In the submerged jet zone and the front of jet impingement zone,the pressure in the center of concentric circles fluctuated and tended to be ascending;in wall jet zone,with a narrow range,the pressure in the center of concentric circles fluctuated at relatively low frequency.From the analysis of the evolution of velocity field,the jet was swinging and the mass of high velocity in the axis separated from main flow as time passed by.It was also found that the velocity had the negative correlation with pressure on a fixed point of jet.From the analysis of the evolution of vorticity field,two beams of vorticity in the field were distributed as the shape of lotus root and swung with time.Comparing vorticity field with pressure field,the results showed that it was vortex swinging that caused the jet swing and pressure distribution was also affected by vortices.The submerged jet field had the characteristic of randomness and was strongly turbulent.We reach the general conclusions from evolution of flow field and inherent relationship among velocity,pressure and vorticity,while there still remains many other aspects to be investigated,such as the quantitative analysis of jet swinging.
Jets are widely used in various hydraulic applications.To observe the evolution of flow field and to investigate the mechanism of a submerged jet,Large eddy Simulations(LES) was utilized to simulate flow field with finite volume method(FVM) for discretization and PISO method for pressure calculation.From the analysis of the evolution of pressure field,the contours of pressure presented to be a cluster of concentric circles,and high pressure and low pressure circles appeared alternately along the jet axis.During the jet impinging,the concentric circles were moving along the jet with deformation,further splitting and merging.In the submerged jet zone and the front of jet impingement zone,the pressure in the center of concentric circles fluctuated and tended to be ascending;in wall jet zone,with a narrow range,the pressure in the center of concentric circles fluctuated at relatively low frequency.From the analysis of the evolution of velocity field,the jet was swinging and the mass of high velocity in the axis separated from main flow as time passed by.It was also found that the velocity had the negative correlation with pressure on a fixed point of jet.From the analysis of the evolution of vorticity field,two beams of vorticity in the field were distributed as the shape of lotus root and swung with time.Comparing vorticity field with pressure field,the results showed that it was vortex swinging that caused the jet swing and pressure distribution was also affected by vortices.The submerged jet field had the characteristic of randomness and was strongly turbulent.We reach the general conclusions from evolution of flow field and inherent relationship among velocity,pressure and vorticity,while there still remains many other aspects to be investigated,such as the quantitative analysis of jet swinging.
引文
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[14]Jiao Aiping,Zhang Chunman,Liu Peiqing.Numerical simulation of flow field characteristics of multi-level jet impinged into a plunge pool[J].Journal of Irrigation and Drainage,2007,26(3):60-65.[焦爱萍,张春满,刘沛清.多层水股射流在水垫塘内流场特性的数值模拟[J].灌溉排水报,2007,26(3):60-65.]
[15]Jiang Ping,Guo Yincheng,Zhang Huiqiang,et al.Large eddy simulation of rectangul ar jets[J].Journal of Tsinghua University(Science and Technology),2004,44(5):689-692.[蒋平,郭印诚,张会强,等.矩形射流流动的大涡模拟[J].清华大学学报(自然科学版),2004,44(5):689-692.]
[16]Li Guoneng,Zhou Hao,Yang Hua,et al.Numerical study of turbulent jet in cross-flow[J].Proceedings of the CSEE,2007,27(2):87-91.[李国能,周昊,杨华,等.横流中湍流射流的数值研究[J].中国电机工程学报,2007,27(2):87-91.]
[17]Cavar D,Meyer K E.LES of turbulent jet in cross flow:Part 2-POD analysis and identification of coherent structures[J].International Journal of Heat&Fluid Flow,2012,36(2):35-46.
[18]Li Z W,Huai W X,Qian Z D.Large eddy simulation of a round jet into a counterflow[J].Science China,2013,56(2):484-491.
[19]刘沛清.自由紊动射流理论[M].北京:北京航空航天大学出版社,2008:23-43.
[2]Burattini P,Antonia R A,Rajagopalan S,et al.Effect of initial conditions on the near-field development of a round jet[J].Experiments in Fluids,2004,37(1):56-64.
[3]Zhu Minming,Zhao Pinghui,Chen Yiliang,et al.The vorticity field of acoustic modulated free jets[J].Journal of Engineering Thermophysics,2012,33(10):1811-1820.[朱旻明,赵平辉,陈义良,等.声激励下自由射流的涡量场[J].工程热物理学报,2012,33(10):1811-1820.]
[4]Karagozian A R.The jet in crossflow[J].Physics of Fluids,2014,1013(3):1-17.
[5]Cortelezzi L,Karagozian A R.On the formation of the counter-rotating vortex pair in transverse jets[J].Journal of Fluid Mechanics,2001,446:347-373.
[6]Broadwell J E,Breidenthal R E.Structure and mixing of a transverse jet in incompressible flow[J].Journal of Fluid Mechanics,1984,148:405-412.
[7]刘沛清,高季章,李永梅.高坝下游水垫塘淹没冲击射流实验[J].中国科学(E辑),1998,28(4):370-377.
[8]Liu Peiqing,Li Futian,Wang Ying.Experimental study on controlling parameters of flow in plunge pools and corresponding impact pressure characteristics[J].Journal of Hydraulic Engineering,2003,34(3):25-28.[刘沛清,李福田,王颖.挑跌流水垫塘内流态结构控制参数与冲击压力变化规律实验研究[J].水利学报,2003,34(3):25-28.]
[9]Liu Chao,Li Longguo,Li Naiwen.Research on instantaneous flow characteristics of the falling submerged jet in a pool based on PIV technique[J].South-to-North Water Transfers and Water Science&Technology,2015,13(3):471-476.[刘超,李龙国,李乃稳.利用PIV技术对淹没射流瞬时流场特性的研究[J].南水北调与水利科技,2015,13(3):471-476.]
[10]Li Naiwen,Li Longguo,Zhuang Wenhua,et al.Hydraulic characteristics of the wall-jet region in a pool with an oblique submerged jet[J].Journal of Sichuan University(Engineering Science Edition),2015,47(3):14-20.[李乃稳,李龙国,庄文化,等.水垫塘冲击射流附壁区的水力特性[J].四川大学学报(工程科学版),2015,47(3):14-20.]
[11]Li Naiwen,Liu Chao,Li Longguo.Turbulent characteristics of plunging region of oblique submerged jet in plunge pool[J].Journal of Hydroelectric Engineering,2016,35(3):66-72.[李乃稳,刘超,李龙国.斜向射流入水垫塘淹没射流区的紊动特性[J].水力发电学报,2016,35(3):66-72.]
[12]Xu Weilin,Liao Huasheng,Yang Yongquan,et al.Numerical simulation of 3-D turbulent flows of plunge pool and energy dissipation analysis[J].Journal of Hydrodynamics,1996,11(5):561-569.[许唯临,廖华胜,杨永全,等.水垫塘三维紊流数值模拟及消能分析[J].水动力学研究与进展,1996,11(5):561-569.]
[13]Diao Mingjun,Yang Yongquan,Wang Yurong,et al.Numerical simulation of water-air two-phase jet flow from flip bucket to plunge pool[J].Journal of Hydraulic Engineering,2003,34(9):77-82.[刁明军,杨永全,王玉蓉,等.挑流消能水气二相流数值模拟[J].水利学报,2003,34(9):77-82.]
[14]Jiao Aiping,Zhang Chunman,Liu Peiqing.Numerical simulation of flow field characteristics of multi-level jet impinged into a plunge pool[J].Journal of Irrigation and Drainage,2007,26(3):60-65.[焦爱萍,张春满,刘沛清.多层水股射流在水垫塘内流场特性的数值模拟[J].灌溉排水报,2007,26(3):60-65.]
[15]Jiang Ping,Guo Yincheng,Zhang Huiqiang,et al.Large eddy simulation of rectangul ar jets[J].Journal of Tsinghua University(Science and Technology),2004,44(5):689-692.[蒋平,郭印诚,张会强,等.矩形射流流动的大涡模拟[J].清华大学学报(自然科学版),2004,44(5):689-692.]
[16]Li Guoneng,Zhou Hao,Yang Hua,et al.Numerical study of turbulent jet in cross-flow[J].Proceedings of the CSEE,2007,27(2):87-91.[李国能,周昊,杨华,等.横流中湍流射流的数值研究[J].中国电机工程学报,2007,27(2):87-91.]
[17]Cavar D,Meyer K E.LES of turbulent jet in cross flow:Part 2-POD analysis and identification of coherent structures[J].International Journal of Heat&Fluid Flow,2012,36(2):35-46.
[18]Li Z W,Huai W X,Qian Z D.Large eddy simulation of a round jet into a counterflow[J].Science China,2013,56(2):484-491.
[19]刘沛清.自由紊动射流理论[M].北京:北京航空航天大学出版社,2008:23-43.