不同上下游倒悬比琴键堰泄流特性试验研究

Experimental study on discharge characteristics of different upstream-downstream overhang ratios of piano key weir

琴键堰是一种新型的迷宫堰,具有超强的泄流能力,受地形限制影响小等特点,被认为是目前解决水库泄流能力不足的有效方案之一。为了弄清楚琴键堰关键体型参数之一——上下游倒悬比(Bo/Bi)对其泄流能力的影响规律,在长16m、宽0.5m、深0.75m的矩形钢化玻璃水槽中建立了三种不同上下游倒悬比的琴键堰模型并分别进行了19种不同流量工况下的过流试验,得到了对应工况时水面线的高清实拍照片和琴键堰的上下游水位等信息。结果表明:不同上下游倒悬比的琴键堰模型上的自由表面均呈现有随流量增大而由水平到弯曲再到大斜率倾斜的变化过程。对于Bo/Bi大于1的琴键堰模型,Bo/Bi越大,琴键堰的超泄比越大且泄流能力也越强。当Bo/Bi为2.5时,其泄流量最大比Bo/Bi=1时提高约16%。另外,通过量纲分析的方法,进一步拟合了含多参数、高精度的琴键堰泄流系数公式。

Piano key weir is a new type of labyrinth weir with the characteristics of ultra-strong discharge capacity and less impact from the limitation of landform,etc.,and then is considered to be one of the effective schemes for solving the problem of insufficient discharge capacity of reservoir at present.In order to make clear about the law of the influence from one of the key shape parameters——upstream-downstream overhang ratio(Bo/Bi)on the discharge capacity of the weir,three models of piano key weir with different upstream-downstream overhang ratios(Bo/Bi)are established in rectangular tempered glass flume with length of 16m,width of 0.5m and depth of 0.75m,from which the flow-passing experiments under 19 different discharge conditions are respectively carried out,thus the high-definition photos of water surface profile and the information of the upstream-downstream water levels for the corresponding working conditions are obtained.The result shows that the free surfaces of the models with different upstream-downstream overhang ratios exhibit the changing processes from horizontal to bending and then to the declination with large gradient.For the piano key weir with Bo/Bi ratio>1,the larger the Bo/Bi ratio is,the larger the over-discharge ratio is to be and the stronger the discharge capacity is to be as well.When Bo/Bi ratio of 2.5,the maximum discharge is to be increased by about 16%than that of Bo/Bi=1.Additionally,the discharge coefficient formula of piano key weir with several parameters and high accuracy is further fitted through the relevant dimensional analysis method.