水闸水力计算

一、闸孔宽度的确定1、流量计算南沙平原总面积741.9km2, 72小时设计暴雨值20年一遇为258mm。 产流计算采用初损后损法。南沙平原为沙性土，初损取30mln,后损取每 小时0.5mm。设三日洪水总量为QoQ= （0.258m-0.03m-0.0005mX72） X741.9X 106nr=0.192mX741.9X 106m3=14244.48 万 in3南沙平原为河网地区，钱塘江一线排涝闸共11座，闸孔总宽为192H1O 外六工段闸分得三日排涝流量为2826.58万m3外六工段闸平均流量 Q=2826.58 X 104/72X 60 X60 X 50%=218,lm3/s0 2、闸孔总宽度计算外六工段及相关地段潮汐特征表：（85国际：米）地点项目外六工段外四工段盐官备注历史最高潮位7.837.928.03平均高潮位3.994.113.92平均低潮位1.191.840.66历史最低潮位-1.65-0.77-2.32百年一遇高潮位7.938.077.83五十年一遇高潮位7.677.837.59二十年一遇高潮位7.287.447.26百年一遇低潮位-1.65-0.77-2.32五十年一遇低潮位-1.09-0.47-1.57二十年一遇低潮位-0.630.01-1.12注：摘自萧围萧围北线外六工段至外八工段标准塘轴线调整（即新围2000)亩工程初步设计内河起排水位4.3m (85国际，下同)，外江水位取平均高潮位3.99m, 闸底板高程1,21110应用宽顶堰流量公式推算水闸总宽：-e-m72g H0THo=H +六 2g式中：。一淹没系数E 一侧收缩系数Ho 堰顶全水头(111)m流量系数Q过闸流量(n/s)Vo上游行近流速H上游水深11/H=(3.99-1.2)/ (4.34.2) =2.79/3.1=0.9查表得淹没系数为。=0.83侧收缩系数定为1流量系数m一般取0.385宽顶堰流量公式简化为:Ho和V。都是未知，须进行试算:第一次试算:不计行近流速，H0=H=4.3-1.2=3.1m= - an2gH 亍Bi =21&121&10.83x0.385j2x9.81x3.l0.83x0385x4.43x5.49VOi=- X xl218.1218.1、,% = 2.506m/s28.07x3.1 87.017H。 = H +2g= 3.1 + 2 506 = 3.1 + 0.320= 3.420m2x9.81第二次试算:Q ) -oinV2gH0/218.121&10.83x0.3855/2 x9.81x3.420t O.83xO.385x 4.43x6.325 8.954= 2436111B. xH218.12436x3.12184 = 2.888m/ s75.516%-2.888-Hp = 3.1 += 3.1 += 3.1 + 0.425 = 3.5 25m2g2x9.81第三次试算:21&121&1218.1B3 = j- = 23.2 &n0.83x 038572 x 9.81 x3.5257 0.83x0.385x4.43x6.618 9.368218.123.28x3.1218, = 3.022 m/ s72.168V 23 0222Hg = H += 3.1 + =3.1 + 0.465 = 3.5651112g2x9.81Hg - $ 3.565-3.525 0.04= 0.01122=1.12%5%Hq33.5653.565满足精度要求,Ho Hg =3.565m21a121&130.83x0.385x V2x9.81x3.565522.89m0.81x0385x4.43x6.731 9.528取B=24m,即4孔6m,中墩宽为1为闸底板高程1.2m （85国标）二、流量计算1、设计流量计算采用宽堰流量公式Q =(7- in n b0 2Ho=H + M2g式中：。一淹没系数E 侧收缩系数m流量系数n一闸孔数b o一单孔净宽(m)H。一堰顶全水头(m)vo上游行近流速(111/S )H上游水深(in)内河起排水位4.3m (85国际，下同)，外江水位取平均高潮位3.99m, 闸底板高程12n。(图应用宽顶堰流量公式推算设计流量：由 li/H=(3.99-1.2)/(4.3-1.2) =2.79/3,1=0.9 查表得淹没系数为。=0.83；由于为无坎高宽顶堰,流量系数m取0385； n=4, b0=6m；侧收缩系数 e由下面三式进行计算：q(n-l) + 11=1-0.171x(1-)x4/ +d2)=1-0.171x（1八1*/网+ + 4）E z中间闸孔侧收缩系数E b-边闸孔侧收缩系数dz中间闸墩厚度拆一边闸墩顺水流向边向边缘线至上游河道水边线之间的距离根据初步设计三视图,d2=lm； b b=0m=1-0.171x(1-)x4/b0/(b0 + dz)瓦+ &=1-0.171x(1-)x/6/(6 + 1)6 + 1= 1-0.171x0.1429x0.9622= 1-0.024=0.976=1-0.171x(1-“小口/网+2 + 风) b0 + j + A V6 I 1= 1-0.171x(1) x y 6 /(6 + _ + 0)6+-+0 Y 22-1-0.171x0.077x0.980= 1-0.013=0.987= 0.984J(n 1) + 4 _ 0 987(4 1) +0.976 _ 3.937n44Ho和V。都是未知，须进行试算确定设计流量:第一次试算：不计行近流速，H0=H=4.3-1.2=3.1m 3 3Q =。 n】en02 = 0.83x0.385x0.984x4x6x72x9.81x3.12=7.546x4.43x5.45 8=18245m3/s18Z4583.70(n x bb + 3) x HQi18245(4x6 + 3)x3.1=2.180in/sH01 = H + 3 = 3.1 + 2 180 =3.1 + 0.242= 3.342m01 2g 2x9.81第二次试算:_3 IQ2 = er m n b0 = 0.83x0.385x0.984x4x6x V2x9?81x3.3422=7.546x 4.43x6.110= 20425m3 / s20425(nx%+3)xH(4x6 + 3)x3.1204.25,= 2.440ni/s83.7% =H +纹= 3.1+ 244(r = 3.1 + 0303= 3.4031】2g2x9.81第三次试算:L 3/ 2Q = bm en b J2gH= 0.83x0.385x0.984x4 x6 x V2 x9.81x3.4032 =7.546x4.43x6.278= 209.87m3/s209.87(n x 1 + 3) x H (4x6 + 3)x3.1209.87 、, =2.507m/s83.7Hn, = H+- = 3.12g2.5072+2x9.81= 3.1 + 0.320=3.420111第四次试算:Q4 = cr mn b0 - y2U032 = 0.83x0.385x0.984x 4 x6x 72791 x3.4202=7.546x 4.43x 6.325 = 21 L44m3 / sq421L44(n x bj + 3) x H (4 x 6 + 3) x 3.1211.44z=2.526iii/s83.7%=H += 3.1 + 2526 = 3.1 + 0.325 = 3.425m2g 2x9.81HQ4-HQ3Hg3.425-3.420_ 3.4250.005=0.0015= O.15%5%3.425满足精度要求,Ho a - =3.425nQ = a- in , n bb 2 = 0.83x0.385x0.984x4x6x 72 x9.81 x3.4252=7.546x 4.43x6339= 211.9 hn3 / s得设计流量：Q=211.91nij/s2、最大流量计算根据表1-1,当外江为平均低潮位时将为自由出流，。=1。水闸四 孔全开时将有最大流量Qmax，Qmax也要经过试算求得。第一次试算： 不计行近流速，H0=H=4.3-1.2=3.1m3 3Qz = m. n 4 /Ih亍=0.385x0.984x4x6x 72x9.81 x3.1- = 9.092x4.43x5.458= 219.83m3/sQmx _(n x 4 + 3) x H219.83(4x6 + 3)x3.l -2198383.7=2.626in/s%2.626-H01 = H + -51- = 3.1 += 3.1 + 0.351= 3.45 hn2g2x9.81第二次试算：L 3 2Qmax2 = nif 11 b0 , j2gHo5 = 0.385x0.984x4x6x V2 x9.81x3.4512 =9.092x 4.43x6.411= 25 &22m3 / s “ Qm25&2225822,Vp = 3.085m/s(nxbb+3)xH (4x6 + 3)x3.183.7Yn23.0852%=H + 且=3.1 += 3.1 + 0.486= 3.5 88n2g2x9.81第三次试算：3 3Qmax3 = ni- f ii-b0 .= 0385x0.984x4x6 x V2x9.81x3.586227352273.5283.7= 3.26 811/s= 9.092x4.43x6.791= 27A52m3/s(n x a + 3) x H (4 x 6 + 3) x 3.1H += 3.1+ 3 26* = 3.1 + 0.545 = 3.645m2g2x9.81第四次试算:L 3I 2Qnux4 = ni en,4，2gHo35 = 0385x0.984x4 x6x V2 x9.81 x3.6452= 9.092x4.43x6.959= 28Q29in3/s280.29(nx%+3)xH(4x6 + 3)x3.1280.29=3.345n/s83.7Hw =H += 3.1 + 34* = 3.1 + o.572= 3.6721112g2x9.81第五次试算:-3/ 2Q5 = 11111 -TlgHoji =0.385x0.984x4x6xV29?81x3.6722 = 9.092x4.43x7.036= 283i39iii3/sQmax528339(n x + 3) x H(4x6 + 3)x3.128339z=3.386m/s83.7Hns = H+- = 3.1 +2g3.386 =3.1 + 0.584= 3.6 84n2x9.81h05-h(mHo53.684-3.672 0.0123.684=0.0033= 0.33% 5% 3.684满足精度要求,Ho Hqj =3.68411 3 3Qm =menbb iHo5 = 0.385x0.984x4x6xV2x9.81 x3.6842 = 9.092x4.43x7.071= 284.80m3/s得设计最大流量:Qmax=284.80m3/s三、消能设计1、消力池池深计算（1）计算消力池深度的流量确定将消力池初始工况设为上游为起排水位4.3m,下游平均低潮位。下游平均低潮湿位为1.99m （表而闸低板高程为1.2m,所以初始工况为下游无水。用式公d =计算消力池深度。（如图31）图3-1从式d =-11 - Az中不难看出当h；最大时所需的池深最深，当闸门拉启，随着流量的增大，下游水深也会逐渐上升。因此最大流量时 往往得出的最大，池深也不是最深。应通过试算各种流量下的 h/ -h/的差距，当h-儿最大时选用这时的流量作为计算池深的流量C2、消力池池长计算由于水跃长度与下游水深关系不大，消力池池长计算的流量取最大流 量 001蚀=284.80111%。消力池长度为：k = Ls +/?Lj4消力池长度L,消力池斜坡段水平投影长度Lj 一自由水跃长度夕一水跃长度校正系数自由水跃长度计算采用欧氏公式：匕=6.9（h一 h Jh一设池后最大流量时的跃后水深限一设池后收缩水深%消力池底算起的总势能q过闸单宽流量a水流动量校正系数（取1.0）g重力加速度（取9.8m/sD。一流速系数（取0.95）284 80q = Qmx /（24 + 3）= _ = 10.55m3（s m）/ fd消力池池深（1.2m）H上游水深（4.3-L2=3ni）Vo一最大流量时的行近流速（3.39m/s）V 33 jo2或=d + H +_ = L2 + 3.l+= 43 + 0.60=4.901112g2x9.8由公式心转+黑=。移项变为工2备募则6.2886.288.=1.4101114.9-1.739由于本闸设计消力池首端、末端相等I =21+t-1二四仙+ 10高；29.8xl.413,W+38x 27.47= 0.71x(5.78-1)= 0.71x4.78=3.39m自 由水跃长度Lj =6.9& -hj = 6.9(3.39-1.41) = 6.9x1.98 = 13.60ni由于池深1.2m消力池斜坡比例设计为1：5,消力池斜坡段水平投影长度 L； = 5 xl.2 = 6in oLq = L, +/JLj = 6 + 0.8x13.6 = 16.88tn所以定消力池长为18m,其中斜坡段水平投影长度6m,水平段12m。