CIV E 530 - OPEN-CHANNEL HYDRAULICS
SPRING 2012
HOMEWORK No. 6

  1. Given the following data for three trapezoidal channels:

    ChannelQ
    (m3/s)    		zSonVmax
    (m/s)
    16020.0040.041.8
    2802.50.002 0.031.5
    375 30.00150.0351.2

    in which Vmax = maximum permissible velocity. What is the design bottom width (with accuracy to within one-tenth of a meter) required to satisfy the specified maximum permissible velocity? Use ONLINE CHANNEL 01.

  2. A channel has the following data:   Q = 330 cfs, z = 2, n = 0.025, and S = 0.0018. Use ONLINE TRACTIVE FORCE to calculate the bottom width and depth under the following conditions:

    • The particles are moderately angular and of size d25 = 0.9 in.

    • The particles are of the same size as in (a), but they are moderately rounded.

    Report the angle of repose θ for cases (a) and (b). Discuss how the particle shape affects the design.

  3. A channel has the following data:   Q = 60 m3/s, z = 2, n = 0.03, and S = 0.0006. Use ONLINE TRACTIVE FORCE to calculate the bottom width and depth under the following conditions:

    • The particles on the sides are slightly angular and of size d25 = 35 mm; the particles on the bottom are of size d50 = 5 mm.

    • The particles on the sides are the same as in (a), but the particles on the bottom are smaller, of size d50 = 4 mm.

    Both cases (a) and (b) have low content of fine sediment in the water and the channel sinuosity is none. Discuss how the bottom particle size affects the design.

  4. A certain type of lawn has a critical shear stress of 30 N/m2. The dimensionless Chezy friction factor f is 0.0075. What is a good estimate of the critical velocity?