前置掺气坎阶梯溢洪道近壁掺气特性
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摘要
为更清楚地认识前置掺气坎阶梯溢洪道近壁面沿程掺气规律,对其掺气特性进行了研究,得到了在不同坡度、单宽流量、台阶体型条件下阶梯竖直面和水平面近壁处掺气浓度沿程分布规律,并与不设前置掺气坎但设置过渡阶梯溢洪道的掺气规律进行了对比分析。研究表明:前置掺气坎式阶梯溢洪道中阶梯水平面与竖直面掺气浓度沿程的分布规律相似,受前置掺气坎的帮助,掺气浓度很高,沿程逐渐减小,达到一定距离后趋于稳定;掺气浓度随单宽流量的增大而减小,随坡度的减缓而减小;前置掺气坎克服了过渡阶梯存在前几级的底部清水区的缺陷,能够用于更大单宽流量。
Pre-aerator stepped spillways,where the aerator is placed prior to the primary step in the stepped spillway,can form a cavity chamber at the bottom to produce enough aeration concentration to avoid the cavitation erosion. To make a better understanding of the bottom aeration characteristics along the pre-aerator stepped spillways,laboratory experiments were carried out,in which aeration concentration distributions on the vertical and horizontal planes along the stepped spillway with different discharges and slopes were investigated. Ulteriorly,comparation of aeration characteristics was made between the pre-aerator stepped spillway and the transitional stepped spillway. It was showed that distribution of aeration concentration on the horizontal surfaces of the pre-aerator stepped spillway was similar to that on the vertical plane. Because of the pre-aerator,the aeration concentration is very high along the primary steps,decreases along the stepped spillways,and tends to the stability for a certain distance. With the increase of discharge per unit width and the decrease of the slope,the aeration concentration decreases. The results indicate that the pre-aerator can eliminate the clear water zone on the bottom of the primary steps,where the transitional steps cannot avoid. Therefore the pre-aerator stepped spillways can be widely used for larger discharges per unit width.
Pre-aerator stepped spillways,where the aerator is placed prior to the primary step in the stepped spillway,can form a cavity chamber at the bottom to produce enough aeration concentration to avoid the cavitation erosion. To make a better understanding of the bottom aeration characteristics along the pre-aerator stepped spillways,laboratory experiments were carried out,in which aeration concentration distributions on the vertical and horizontal planes along the stepped spillway with different discharges and slopes were investigated. Ulteriorly,comparation of aeration characteristics was made between the pre-aerator stepped spillway and the transitional stepped spillway. It was showed that distribution of aeration concentration on the horizontal surfaces of the pre-aerator stepped spillway was similar to that on the vertical plane. Because of the pre-aerator,the aeration concentration is very high along the primary steps,decreases along the stepped spillways,and tends to the stability for a certain distance. With the increase of discharge per unit width and the decrease of the slope,the aeration concentration decreases. The results indicate that the pre-aerator can eliminate the clear water zone on the bottom of the primary steps,where the transitional steps cannot avoid. Therefore the pre-aerator stepped spillways can be widely used for larger discharges per unit width.
引文
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[9]陆芳春,包中进,徐岗.阶梯式溢流面水力特性规律研究[J].浙江水利科技,2008(2):34-35.(LU Fangchun,BAO Zhongjin,XU Gang.Research on hydraulic characteristic regularity for benched spillway face[J].Zhejiang Hydrotechnics,2008(2):34-35.(in Chinese))
[10]夏毓常,张黎明.水工水力学原型观测与模型试验[M].北京:中国电力出版社,1999:5-6.(XIA Yuchang,ZHANG Liming.Prototype observation and model test for engineering hydraulic[M].Beijing:China Electric Power Press,1999:5-6.(in Chinese))
[2]郑阿漫.掺气分流墩台阶式溢洪道水力特性的研究[D].西安:西安理工大学,2001.(ZHENG Aman.Hydraulics of stepped spillways with aerated splitter[D].Xi'an:Xi'an University of Technology,2001.(in Chinese))
[3]张志昌,曾东洋,刘亚菲.台阶式溢洪道掺气特性的试验研究[J].应用力学学报,2003,20(4):97-100.(ZHANG Zhichang,ZENG Dongyang,LIU Yafei.Experimental investigation on the characteristic of air entrainment on the stepped spillways[J].Chinese Journal of Applied Mechanics,2003,20(4):97-100.(in Chinese))
[4]PFISTER M,HAGER W H,MINOR H E.Bottom aeration of stepped spillways[J].Journal of Hydraulic Engineering,2006,132(8):850-853.
[5]PFISTER M,HAGER W H,MINOR H E.Stepped chutes:Pre-aeration and spray reduction[J].International Journal of Multiphase Flow,2006,32(2):269-284.
[6]PFISTER M,HAGER W H.Self-entrainment of air on stepped spillways[J].International Journal of Multiphase Flow,2011,37(2):99-107.
[7]彭勇,张建民,许唯临,等.前置掺气坎式阶梯溢洪道掺气水深及消能率的计算[J].水科学进展,2009,20(1):63-68.(PENG Yong,ZHANG Jianmin,XU Weilin,et al.Calculation of aerated water depth and energy dissipation rate of a pre-aerator stepped spillway[J].Advances in Water Science,2009,20(1):63-68.(in Chinese))
[8]陈剑刚,张建民,许唯临.前置掺气坎式阶梯溢洪道体型特点及工程应用试验研究[J].四川大学学报:工程科学版,2010,42(6):6-11.(CHEN Jiangang,ZHANG Jianmin,XU Weilin.Practical engineering application and hydraulic characteristics of the flow in stepped spillway with pre-aerator slot[J].Journal of Sichuan University:Engineering Science Edition,2010,42(6):6-11.(in Chinese))
[9]陆芳春,包中进,徐岗.阶梯式溢流面水力特性规律研究[J].浙江水利科技,2008(2):34-35.(LU Fangchun,BAO Zhongjin,XU Gang.Research on hydraulic characteristic regularity for benched spillway face[J].Zhejiang Hydrotechnics,2008(2):34-35.(in Chinese))
[10]夏毓常,张黎明.水工水力学原型观测与模型试验[M].北京:中国电力出版社,1999:5-6.(XIA Yuchang,ZHANG Liming.Prototype observation and model test for engineering hydraulic[M].Beijing:China Electric Power Press,1999:5-6.(in Chinese))