水环境课程设计

4--34.某均匀河段长8km，流速u=5km/h，纵向离散系数E=2km2/h，BOD的降解系数K1=0.0151h-1，上游断面有一断面混合均匀的污染源，0~1h间稳定排污，使该断面的污染浓度保持在20mg/L，以后排污停止，试用隐式差分体系计算本河段各断面的BOD浓度变化过程。解：取，根据题中所给资料，按（1）计算各节点水质迁移转化方程中的系数ai、bi、ri、di，和按式（2）自i=1至n顺序算出gi、wi；然后逆序从n至1由式（2）求得各节点的含BOD浓度变化过程，公式如下：(1)（2）编制程序运用C语言进行求解程序代码附在最后求得数据如下表1所示时间距离012345678020.0000.0000.0000.0000.0000.0000.0000.0000.000120.00015.4745.3231.8310.6300.2170.0750.0260.009220.00018.06813.7577.3273.4131.4810.6150.2480.098320.00018.99616.77412.9688.2024.5432.3051.1000.501420.00019.42218.15915.88512.5288.6455.3333.0171.598520.00019.64418.88017.47315.24312.2408.9015.8983.610620.00019.76819.28418.38716.90914.75912.0319.0636.315720.00019.84219.52318.93517.94616.44014.37811.8669.173820.00019.88719.66919.27418.60317.55216.04314.06811.732920.00019.91519.76219.48919.02718.29117.20015.70313.8091010.00019.93319.82119.62819.30418.78518.00016.88515.407时间距离91011121314151600.0000.0000.0000.0000.0000.0000.0000.00010.0030.0010.0000.0000.0000.0000.0000.00020.0380.0150.0060.0020.0010.0000.0000.00030.2210.0950.0400.0160.0070.0030.0010.00040.8030.3880.1810.0820.0360.0160.0060.00152.0711.1260.5850.2930.1420.0660.0280.00664.0992.5021.4490.8020.4260.2170.1010.02876.6334.5042.8881.7601.0240.5670.2890.10189.2506.8834.8413.2292.0491.2350.6870.288911.6189.3077.0835.1233.5242.3001.3930.6861013.58811.5199.3477.2435.3533.7602.4681.391表1各断面各时段BOD浓度数据表（单位：mg/L）由表1可以画出河段各断面BOD浓度随时间变化过程，如图1.附-----------------------------------------------------C语言程序代码%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%已知量%L为河段长，为8km%u为流速，为5km/h%E为纵向离散系数，为2km2/h%k1为BOD的降解系数，为0.0151/h%T为污染物排放时间，为1h%CO初始位置污染物的浓度，为10mg/LL=8;u=5;E=2;k1=0.0151;T=1;CO=20;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%分段%x为所取断面的间距，设为0.5km%t为测各断面浓度的时间间隔，设为0.1h%n1为监测断面总数%n2为时间点总数x=0.5;t=0.1;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%相关系数的计算a=-E/(x^2);b=1/t+2*E/(x^2)+k1/2;r=a;d=1/t-u/x;e=u/x-k1/2;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%设置边界条件result=zeros(11,17);result(1:10,1)=CO;A=zeros(11,17);g=zeros(11,17);w=zeros(1,17);%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%生成w矩阵w(1,2)=r/b;fori=3:16w(1,i)=r/(b-a*w(1,i-1));end%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%forj=2:11%生成g矩阵A(j,2)=result(j-1,2)*d+result(j-1,1)*e-a*result(j,1);g(j,2)=A(j,2)/b;fori=3:16A(j,i)=result(j-1,i)*d+result(j-1,i-1)*e;g(j,i)=(A(j,i)-a*g(j,i-1))/(b-a*w(1,i-1));endA(j,17)=result(j-1,17)*d+result(j-1,16)*e;g(j,17)=(A(j,17)-(a-r)*g(j,16))/((b+2*r)-(a-r)*w(