基于平均紊动结构下明渠水流流速分布研究
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摘要
【目的】揭示明渠水流外区域流速分布偏离传统对数定律的潜在机理。【方法】基于猝发现象,根据雷诺纳维-斯托克斯方程推导出了描述明渠水流流速分布的改进模型,并通过多组试验工况对改进模型的准确性进行了验证。【结果】(1)该模型的分析结果与明渠中内/外区域的流速分布均吻合较好,仅有1.1%左右的误差;(2)将试验结果与当前应用较为广泛的YL、ML和CL定律对比,这些定律预测的结果与外层区域的实测数据相比分别存在3.1%、4.5%、5.2%左右的误差。【结论】二维均匀流中存在尾流定律的原因来自于流速的上下紊动,这种紊动造成外区水流的流速微降。
【Objective】The objective of this paper is to disentangle the underlying mechanisms that the distribution of water velocity in the outer region of open channel deviates from the log-law.【Method】We developed a new analytical model, similar to the Reynolds 'average Navier-Stokes equations, by considering the bursts, and then verified it against experimental data.【Result】(1)The results calculated from the proposed model agreed well with the measured velocity distribution in both internal and outer regions of the channel with an error of 1.1%.(2)Compared with experimental velocity distribution, the errors resulted from the commonly used YL, ML and CL law in the literature were 3.1%, 4.5% and 5.2% respectively, much higher than the error of the proposed model.【Conclusion】The underlying mechanisms of the wake law in 2 D uniform channel flow is the result of up-down events, and such a turbulent flow slightly reduced the velocity in the outer region of the open channel.
【Objective】The objective of this paper is to disentangle the underlying mechanisms that the distribution of water velocity in the outer region of open channel deviates from the log-law.【Method】We developed a new analytical model, similar to the Reynolds 'average Navier-Stokes equations, by considering the bursts, and then verified it against experimental data.【Result】(1)The results calculated from the proposed model agreed well with the measured velocity distribution in both internal and outer regions of the channel with an error of 1.1%.(2)Compared with experimental velocity distribution, the errors resulted from the commonly used YL, ML and CL law in the literature were 3.1%, 4.5% and 5.2% respectively, much higher than the error of the proposed model.【Conclusion】The underlying mechanisms of the wake law in 2 D uniform channel flow is the result of up-down events, and such a turbulent flow slightly reduced the velocity in the outer region of the open channel.
引文
[1]韩金旭,李敬茹,杜凯,等.明渠水流测线平均流速横向分布及其应用[J].灌溉排水学报,2013,32(3):71-73.
[2]刘春晶,李丹勋,王兴奎.明渠均匀流的摩阻流速及流速分布[J].水利学报,2005,36(8):950-955.
[3]KELULEGAN G H.Laws of turbulent flow in open Channels[J].Journal of Research of the National Bureau of Standards,1938,21(6):707-741.
[4]雒天峰,吕宏兴,张春景,等.U形渠道横向流速分布规律及测流技术研究[J].灌溉排水学报,2008,27(1):61-64.
[5]陈兴伟,林木生,林炳青.粗糙透水床面明渠水流垂线流速分布的试验研究[J].亚热带资源与环境学报,2012,7(4):16-19.
[6]COLES D.The law of the wake in the turbulent boundary layer[J].Journal of Fluid Mechanics,1956,1(2):191-226.
[7]NEZU I,RODI W.Closure of“open-channel flow measurements with a laser doppler anemometer”[J].Journal of Hydraulic Engineering,1987,113(12):1 574-1 576.
[8]BAI Y,WANG X.Theoretical bend-flow solutions and velocity-dip phenomenon[J].Journal of Hydraulic Research,2016,55(3):1-11.
[9]韩金旭,李敬茹,杜凯,等.明渠水流测线平均流速横向分布及其应用[J].灌溉排水学报,2013,32(3):71-73.
[10]王二平,金辉,张艳艳,等.矩形明渠流速分布特征及其在流量量测中的应用[J].灌溉排水学报,2008,27(4):25-28.
[11]KIRKGOZ M S.Turbulent velocity profiles for smooth and rough open channels-closure[J].Journal of Hydraulic Engineering,1991,117(9):1 221-1 222.
[12]TACHIE M F,BALACHANDA R,BERGSTROM D J.Low Reynolds number effects in open-channel turbulent boundary layers[J].Experiments in Fluids,2003,34(5):616-624.
[13]YANG S Q,LIM S Y,TAN S K.Velocity distribution and dip-phenomenon in smooth uniform open channel flows[J].Journal of Hydraulic Engineering,2004,130(12):1 179-1 186.
[14]LASSABATERE L,JANN HUI P U,BONAKDARI H,et al.Velocity distribution in open channel flows:an analytical approach for the outer region[J].Journal of Hydraulic Engineering,2013,139(1):37-43.
[15]GUO J.Modified log-wake-law for smooth rectangular open channel flow[J].Journal of Hydraulic Research,2014,52(1):121-128.
[16]CELLINO M,LEMMIN U.Influence of coherent flow structures on the dynamics of suspended sediment transport in open-channel flow[J].Journal of Hydraulic Engineering,2004,130(11):1 077-1 088.
[2]刘春晶,李丹勋,王兴奎.明渠均匀流的摩阻流速及流速分布[J].水利学报,2005,36(8):950-955.
[3]KELULEGAN G H.Laws of turbulent flow in open Channels[J].Journal of Research of the National Bureau of Standards,1938,21(6):707-741.
[4]雒天峰,吕宏兴,张春景,等.U形渠道横向流速分布规律及测流技术研究[J].灌溉排水学报,2008,27(1):61-64.
[5]陈兴伟,林木生,林炳青.粗糙透水床面明渠水流垂线流速分布的试验研究[J].亚热带资源与环境学报,2012,7(4):16-19.
[6]COLES D.The law of the wake in the turbulent boundary layer[J].Journal of Fluid Mechanics,1956,1(2):191-226.
[7]NEZU I,RODI W.Closure of“open-channel flow measurements with a laser doppler anemometer”[J].Journal of Hydraulic Engineering,1987,113(12):1 574-1 576.
[8]BAI Y,WANG X.Theoretical bend-flow solutions and velocity-dip phenomenon[J].Journal of Hydraulic Research,2016,55(3):1-11.
[9]韩金旭,李敬茹,杜凯,等.明渠水流测线平均流速横向分布及其应用[J].灌溉排水学报,2013,32(3):71-73.
[10]王二平,金辉,张艳艳,等.矩形明渠流速分布特征及其在流量量测中的应用[J].灌溉排水学报,2008,27(4):25-28.
[11]KIRKGOZ M S.Turbulent velocity profiles for smooth and rough open channels-closure[J].Journal of Hydraulic Engineering,1991,117(9):1 221-1 222.
[12]TACHIE M F,BALACHANDA R,BERGSTROM D J.Low Reynolds number effects in open-channel turbulent boundary layers[J].Experiments in Fluids,2003,34(5):616-624.
[13]YANG S Q,LIM S Y,TAN S K.Velocity distribution and dip-phenomenon in smooth uniform open channel flows[J].Journal of Hydraulic Engineering,2004,130(12):1 179-1 186.
[14]LASSABATERE L,JANN HUI P U,BONAKDARI H,et al.Velocity distribution in open channel flows:an analytical approach for the outer region[J].Journal of Hydraulic Engineering,2013,139(1):37-43.
[15]GUO J.Modified log-wake-law for smooth rectangular open channel flow[J].Journal of Hydraulic Research,2014,52(1):121-128.
[16]CELLINO M,LEMMIN U.Influence of coherent flow structures on the dynamics of suspended sediment transport in open-channel flow[J].Journal of Hydraulic Engineering,2004,130(11):1 077-1 088.