前置掺气坎坡度对阶梯溢洪道掺气水流影响的数值模拟
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摘要
为研究复杂边界条件下气液两相界面的流动及混掺现象对工程建设的影响,结合某大型水电站的溢洪道,利用RNG k-ε模型对其进行三维流场模拟,采用有限体积法离散控制方程,并用GMRES算法进行压力求解,对前置掺气坎式阶梯溢洪道和传统阶梯溢洪道泄流壁面上的高速掺气水流进行数值模拟。结果表明:随着掺气坎坡度的增加,其掺气空腔及掺气浓度均有所增大,随着水流下泄掺气浓度沿程降低,达到一定距离后趋于稳定,掺气浓度值达到了减免空蚀破坏的要求;与传统阶梯溢洪道的模拟结果进行对比可知,增设前置掺气坎后,既可以增加前几级阶梯的掺气浓度使水流提前达到水气平衡,也没有降低阶梯式溢洪道的消能率,为解决传统阶梯溢洪道中出现的工程难题提供了一种新思路。
In order to study the influence of gas-liquid two-phase interface flow and mixing phenomenon on engineering construction under complex boundary conditions,we combined with the medium spillway of a large hydropower station,used the RNG k-ε model to simulate the three-dimensional flow field,used the finite volume method to discretize the governing equation,and used the GMRES algorithm to solve the pressure problem.Numerical simulation of high speed aerated flow on the discharge wall of the pre-aerated stepped spillway and the traditional stepped spillway was carried out.The results show that the aeration cavity and aeration concentration increased with the increase of the slope of the aerator,and the aeration concentration decreased along the flow,until reaches a certain distance,the concentration reaches the requirement of reducing cavitation damage.Compared with the simulation results of the traditional stepped spillway,the addition of the front aerator can increase the aeration concentration of the first several steps,make the flow reach water and gas balance ahead of time,and do not affect the energy dissipation rate of the stepped spillway.This study provides a new way to solve the engineering problems in the traditional stepped spillway.
In order to study the influence of gas-liquid two-phase interface flow and mixing phenomenon on engineering construction under complex boundary conditions,we combined with the medium spillway of a large hydropower station,used the RNG k-ε model to simulate the three-dimensional flow field,used the finite volume method to discretize the governing equation,and used the GMRES algorithm to solve the pressure problem.Numerical simulation of high speed aerated flow on the discharge wall of the pre-aerated stepped spillway and the traditional stepped spillway was carried out.The results show that the aeration cavity and aeration concentration increased with the increase of the slope of the aerator,and the aeration concentration decreased along the flow,until reaches a certain distance,the concentration reaches the requirement of reducing cavitation damage.Compared with the simulation results of the traditional stepped spillway,the addition of the front aerator can increase the aeration concentration of the first several steps,make the flow reach water and gas balance ahead of time,and do not affect the energy dissipation rate of the stepped spillway.This study provides a new way to solve the engineering problems in the traditional stepped spillway.
引文
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[14]陈剑刚,张建民,许唯临.前置掺气坎式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.
[15]吴守荣,张建民,许唯临,等.前置掺气坎式阶梯溢洪道体型布置优化试验研究[J].四川大学学报(工程科学版),2008,40(3):37-42.
[2]李志高,霍静静,向光红.跌坎型底流消能试验研究[J].人民长江,2009,40(23):28-29.
[3]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.
[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]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.
[6]刘善均,朱利,张法星,等.前置掺气坎阶梯溢洪道近壁掺气特性[J].水科学进展,2014,25(3):401-406.
[7]朱利,张法星,刘善均.前置掺气坎高度对阶梯溢流坝水力特性的影响[J].人民黄河,2014,36(6):110-112.
[8]王自明,王斌,包中进.阶梯式消能工与掺气墩在工程中的联合运用[J].人民长江,2016,47(15):78-81.
[9]尹芳芳.带有掺气挑坎的台阶式溢洪道的三维数值模拟[D].西安:西安理工大学,2010.
[10]王月华,包中进,王斌.基于Flow-3D软件的消能池三维水流数值模拟[J].武汉大学学报(工学版),2012,45(2):454-457+476.
[11]包中进,王月华.基于FLOW-3D软件的溢洪道三维水流数值模拟[J].浙江水利科技,2012(2):5-9.
[12]HIRT C W.Modeling turbulent entrainment of air at a free surface[J].Flow Science,2004.
[13]SARFARAZ M.Numerical computation of inception point location for steeply sloping stepped spillways[J].Journal of Lightwave Technology,2009,27(16):3662-3671.
[14]陈剑刚,张建民,许唯临.前置掺气坎式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.
[15]吴守荣,张建民,许唯临,等.前置掺气坎式阶梯溢洪道体型布置优化试验研究[J].四川大学学报(工程科学版),2008,40(3):37-42.