The Islamic University of Gaza Faculty of Engineering Civil Engineering Department Hydraulics - ECIV 3322 Chapter 6 Open Channel

Example 1 Open channel of width = 3m as shown, bed slope = 1:5000, d=1.5m find the flow rate using Manning equation, n=0.025.

Example 2 Open channel as shown, bed slope = 69:1584, find the flow rate using Chezy equation, C=35.

Example 3 Circular open channel as shown d=1.68m, bed slope = 1:5000, find the Max. flow rate & the Max. velocity using Chezy equation, C=70. Max. flow rate

Max. Velocity

Example 4 Trapezoidal open channel as shown Q=10m3/s, velocity =1.5m/s, for most economic section. find wetted parameter, and the bed slope n=0.014.

To calculate bed Slope Eng. Tamer Eshtawi

Example 5 Determine the critical depth if the flow is 1.33m3/s. the channel width is 2.4m

Example 6 Rectangular channel , Q=25m3/s, bed slope =0.006, determine the channel width with critical flow using manning n=0.016

Eng. Tamer Eshtawi

Example 7 A 3-m wide rectangular channel carries 15 m3/s of water at a 0.7 m depth before entering a jump. Compute the downstrem water depth and the critical depth

Example 8 d1=dn d2 dn = Depth can calculated from manning equation

a) d1=dn d2 b)

c) d1=dn d2

Example 9 A trapezoidal channel with a bottom width of 5m, side slope of 1H: 1V, and a Manning n of 0.013 carries a discharge of 50m3/s at a slope of 0.0004. Compute by the direct step method the backwater profile created by a dam that backs up the water to a depth of 6 m immediately behind the dam. The upstream end of the profile is assumed at a depth equal to 1% greater than the normal depth.

determine normal depth, Yn By trial and error, Yn = 2.87 m

determine critical depth, Yc By trial and error, Yc = 1.90 m Control depth = 1.01*2.87 =2.90m

12 11 10 9 8 7 6 5 4 3 2 1 L Δx So-Sfm Sfm Sf ΔE E V R P A y m *104 3.710 3.165 2.182 1.735 13.2 22.91 2.9 1250 0.455 3.545 0.057 3.380 3.222 2.080 1.779 13.49 24.0 3.0 2237 987 0.810 3.190 0.080 3.000 3.303 1.990 1.824 13.77 25.11 3.1 2937 700 1.170 2.830 0.082 2.660 3.384 1.900 1.868 14.05 26.24 3.2 4437 1500 1.732 2.268 0.260 1.875 3.644 1.680 1.997 14.90 29.75 3.5 6187 1750 2.495 1.505 1.135 4.099 1.390 2.207 16.31 36.0 4.0

12 11 10 9 8 7 6 5 4 3 2 1 L Δx So-Sfm Sfm Sf ΔE E V R P A y m *104 1.135 4.099 1.390 2.207 16.31 36.0 4.0 7713 1526 3.075 0.925 0.472 0.715 4.570 1.170 2.411 17.73 42.75 4.5 9123 1410 3.408 0.592 0.481 0.469 5.051 1.000 2.612 19.14 50.0 5.0 10473 1350 3.606 0.394 0.487 0.318 5.538 0.865 2.808 20.56 57.75 5.5 11793 1320 3.729 0.271 0.491 0.223 6.029 0.758 3.005 21.97 66.0 6.0