垂直洞塞出口冲击区壁面压强特性

Characteristics of the Wall Pressure in Impacting Zone at the End of Vertical Plug

垂直洞塞作为一种新型消能工,其出口水流状态可视为淹没射流,出流区域为射流冲击区,受结构自身特点的影响,该类射流的流速大,射流冲击区壁面受到的压强大,为探索垂直洞塞出口冲击区附近有界区域内的壁面压强分布规律,为结构设计及水力设计提供科学依据,作者结合某大型泄洪洞工程,采用模型试验、理论推导及数值模拟相结合的方法,针对不同的出口射流流速及不同压坡位置,研究了垂直洞塞出口射流冲击区的壁面压强特性。结果表明:冲击压强的试验和数值模拟结果吻合良好;当轴线上压强测点同压强最大值处的距离和压强半宽值的比值小于1时,试验及数模得到的壁面压强与理论分析曲线贴合,但当该比值大于1时,且压坡段与射流中心之间距离和射流直径之比较小时,两者结果明显高于理论曲线,理论曲线此时不适用。定量分析表明:随着下游压坡段与射流中心之间距离的增加,底板轴线压强分布逐渐贴合理论曲线;当压坡段与射流中心之间距离和射流直径之比大于2.35时,冲击区下游压坡段位置对底板压强半宽值无显著影响,各试验组次中底板压强半宽约为射流直径的0.3倍;射流冲击区内,顶部和侧壁壁面的压强随着离射流中心的距离减小而降低,在泄洪洞上游封堵处压强达到最大值。

The vertical plug is a new way to dissipate water energy,in which the flow can be regarded as a submerged jet,and the construction leads to the high velocity and pressure on the wall.In order to explore the wall pressure distribution at the impinging zone and offer some scientific evidence for structural and hydraulic design,based on a spillway project,the characteristics of the wall pressure is analyzed by theoretical derivation,experimental test and numerical simulation under the condition of submerged jet with different flow rate.The results indicate that the measured pressure on the bottom axes agrees well with the numerical one,and both results have good agreement with the theoretical curve when the ratio of the distance between the test point and largest pressure point and the length of half maximum pressure is less than 1,but they are much larger than the theory when it is more than 1.The pressure gradually tends to the theoretical curve with the increasing of distance between pressslope and the center of the jet.The half-pressure length,which does not depend on the position of press-slope at the impacting zone downstream when the distance is 2.35 times larger than the jet diameter,is nearly equal to 0.3 times the diameter of the jet.Furthermore,the pressure of the top and side wall is decreasing when approaching to the center of the jet.