节制闸开度对分水口流速分布的影响

Influence of control gate opening on the velocity distribution of bifurcation channel

研究节制闸在调节分水口水位和流量时,闸门开度对分水口附近流速和泥沙分布的影响。采用梯形渠道分水口水力特性试验和数值模拟相结合的方法,对不同闸门开度下闸前主渠道沿程水深的变化规律及闸门开度对分水口附近流速的影响进行研究。结果表明:1)主渠道水深模拟值和实测值的决定系数R^(2)、纳什系数NSE和均方根误差RMSE分别为0.898、0.687和0.361,表明模拟值与实测值吻合度较好,模型比较可靠。2)闸孔出流时,不同闸门开度下,梯形主渠分水口处沿程水深变化规律基本一致,呈现先降低后升高再降低的规律;当来流量为20-30L/s时,闸孔出流和堰流的临界值出现在闸门开度为9-12cm(相对开度为0.78-0.81),即闸孔出流和堰流的分界并非一个定值,还受主渠来流量的影响。3)随闸门开度的增大,纵向流速平面分布逐渐恢复成对数型分布,且分水口处横向流速较纵向流速和垂向流速变化剧烈。4)分水口区域表层流速变化大于底层流速,随着闸门开度的增大,在越靠近分水口中心的区域流速值越小,该区域易形成漩涡与回流区。

To investigate the effect of the gate opening on the flow velocity and sediment distribution near the water diversion when the control gate adjusts the water level and flow of the bleeder.In this study,the variation of water depth along the main channel in front of the gate and the effect of the gate opening on the velocity near the diversion under different gate opening were investigated by combining numerical simulation of hydraulic characteristics at the diversion with different discharge and gate opening.The results show that:1)The determination coefficient(R^(2)),Nash coefficient(NSE),and root mean square error(RMSE)of the simulated and measured values of the water depth of the main channel are respectively 0.898,0.687 and 0.361,suggesting that the simulated values are in good agreement with the measured values and the model is more reliable.2)When water discharges at the lateral gate,the water depth at the diversion of the main channel is basically the same under different gate opening,which decreases first,then increases and then decreases.When the discharge is in the range of 20-30 L/s,the critical value of discharge at the lateral gate and weir flow appears in the range of gate opening is 9-12 cm(relative opening is0.78-0.81)indicating that the boundary between discharge at the lateral gate and weir flow is not a constant value,and also affected by the discharge of the main channel.With the increase of the opening of the gate,the horizontal distribution of the longitudinal velocity gradually returns to the pairwise distribution,and the transverse velocity at the diversion changes more sharply than the longitudinal velocity and the vertical velocity.3)With the increase of gate opening,the horizontal distribution of the longitudinal velocity gradually returns to the logarithm distribution,and the transverse velocity changes more dramatically than the longitudinal velocity and the vertical velocity at the diversion.4)The variation of surface velocity in the diversion area is greater than that at the bottom.With the increase of the gate opening,the velocity value in the area closer to the center of the diversion area is smaller,and the vortex and backflow are easy to form in this area.