河道交汇区涡旋结构研究
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摘要
利用粒子图像测速技术(PIV)实现了基于涡量的剪切层和分离区位置的精确确定,同时对汇流区水平面内的涡旋结构进行系统观测和分析。研究发现:剪切层和分离区近水面和近底面水深平面的涡旋密度大,水深中部的涡旋密度小;支流流量增大的情况下涡旋密度均增大。槽底壁面湍流是近底面涡旋密度大的主要原因。剪切层由水流剪切产生的剪切涡以小旋转强度涡旋为主,分离区由水流分离产生的分离涡以中等及小旋转强度涡旋为主。
Particle image velocimetry(PIV) technique is used to accurately determine the location of shear layer and separation zone based on vorticity. Meanwhile, the vortices in the horizontal plane at the confluence are systematically observed and analyzed. It is found that the vortex density within both the shear layer and the separation zone is larger near the water surface and near the bottom than that in the middle of water depth. The vortex density increases with the increase of tributary discharge when the discharge of main channel is fixed. The high density of vortices near the bottom is caused by the wall turbulence. In addition, the shear layer generated by flow shear is dominated by vortices with small swirling strength, while the separation zone generated by the flow separation is dominated by vortices with medium and small swirling strength.
Particle image velocimetry(PIV) technique is used to accurately determine the location of shear layer and separation zone based on vorticity. Meanwhile, the vortices in the horizontal plane at the confluence are systematically observed and analyzed. It is found that the vortex density within both the shear layer and the separation zone is larger near the water surface and near the bottom than that in the middle of water depth. The vortex density increases with the increase of tributary discharge when the discharge of main channel is fixed. The high density of vortices near the bottom is caused by the wall turbulence. In addition, the shear layer generated by flow shear is dominated by vortices with small swirling strength, while the separation zone generated by the flow separation is dominated by vortices with medium and small swirling strength.
引文
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[18] CHEN Huai,ADRIAN R J,QIANG Zhong,et al.Analytic solutions for three dimensional swirling strength in compressible and incompressible flows[J].Physics of Fluids,2014,26(8):193-208.
[ 2 ] DRUCKER E G,LAUDER G V.Locomotor forces on a swimming fish:three-dimensional vortex wake dynamics quantified using digital particle image velocimetry[J].Journal of Experimental Biology,1999,202(18):2393-2412.
[ 3 ] PENG Jifeng,DABIRI J O.A potential-flow,deformable-body model for fluid-structure interactions with compact vorticity:application to animal swimming measurements[J].Experiments in Fluids,2007,43(5):655-664.
[ 4 ] 顾莉,赵欣欣,戴波,等.汇流比对U形弯曲交汇河道中污染物离散系数的影响[J].河海大学学报(自然科学版),2018,46(3):189-195.(GU Li,ZHAO Xinxin,DAI Bo,et al.The influence of discharge ratio on the pollutant dispersion coefficient in the U-shaped confluent curved river[J].Journal of Hohai University (Natural Sciences),2018,46(3):189-195.(in Chinese))
[ 5 ] WEBER L J,SCHUMATE E D,MAWER N.Experiments on flow at a 90° open-channel junction[J].Journal of Hydraulic Engineering,2001,227(5):340-350.
[ 6 ] YUAN Saiyu,TANG Hongwu,XIAO Yang,et al.Water flow and sediment transport at open-channel confluences:an experimental study[J].Journal of Hydraulic Research,2017,56(3):333-350.
[ 7 ] RHOADS B L,SUKHODOLOV A N.Lateral momentum flux and the spatial evolution of flow within a confluence mixing interface[J].Water Resources Research,2008,44(8):134-143.
[ 8 ] BEST J L.Flow dynamics at river channel confluences:implications for sediment transport and bed morphology[J].Recent Developments in Fluvial Sedimentology,1987,39:27-35.
[ 9 ] YUAN Saiyu,TANG Hongwu,XIAO Yang,et al.Turbulent flow structure at a 90-degree open channel confluence:accounting for the distortion of the shear layer[J].Journal of Hydro-environment Research,2016,12:130-147.
[10] 王协康,王宪业,卢伟真,等.明渠水流交汇区流动特征试验研究[J].四川大学学报(工程科学版),2006,38(2):1-5.(WANG Xiekang,WANG Xianye,LU Weizhen,et al.Experimental study on flow structure at open channel confluences[J].Journal of Sichuan University(Engineering Science Edition),2006,38(2):1-5.(in Chinese))
[11] 刘同宦,郭炜,詹磊,等.主支汇流比对交汇区域水流脉动特性影响试验[J].水利水电科技进展,2009,29(3):6-8.(LIU Tonghuan,GUO Wei,ZHAN Lei,et al.Experiment on the influence of discharge ratio of main flow of tributary on flow fluctuation characteristics in confluence area[J].Advances in Science and Technology of Water Resources,2009,29(3):6-8.(in Chinese))
[12] 刘盛赟,康鹏,李然,等.水流交汇区的水动力学特性数值模拟[J].水利水电科技进展,2012,32(4):14-18.(LIU Shengyun,KANG Peng,LI Ran,et al.A numerical study on hydrodynamic characteristics of confluence flow[J].Advances in Science and Technology of Water Resources,2012,32(4):14-18.(in Chinese))
[13] ZHONG Qiang,LI Danxun,CHEN Qigang,et al.Coherent structures and their interactions in smooth open channel flows[J].Environmental Fluid Mechanics,2015,15(3):653-672.
[14] 陈凯霖,冯民权,张涛.基于PIV技术的明槽交汇区流场试验研究[J].水力发电学报,2018,37(11):43-55.(CHEN Kailin,FENG Minquan,ZHANG Tao.Experimental study on open-channel flow confluence based on PIV technology[J].Journal of Hydroelectric Engineering,2018,37(11):43-55.(in Chinese))
[15] K?HLER C J,ASTARITA T,VLACHOS P P,et al.Main results of the 4th International PIV Challenge[J].Experiments in Fluids,2016,57(6):97-167.
[16] LANDRETH C C,ADRIAN R J.Impingement of a low Reynolds number turbulent circular jet onto a flat plate at normal incidence[J].Experiments in Fluids,1990,9(1):74-84.
[17] 陈启刚,陈槐,钟强,等.高频粒子图像测速系统原理与实践[M].北京:清华大学出版社,2005:138-139.
[18] CHEN Huai,ADRIAN R J,QIANG Zhong,et al.Analytic solutions for three dimensional swirling strength in compressible and incompressible flows[J].Physics of Fluids,2014,26(8):193-208.