Cu06997 lecture 9-10_exercises

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Cu06997 lecture 9-10_exercises

  1. 1. Exercise 1Clean and straight natural channelBed slope 1:2000, Length = 1000 mAssuming steady uniform flow1. Calculate the velocity and discharge usingManning , assume n = 0,02 s/m1/32. Calculate the mean boundary shear stress3. Is the flow turbulent?4. Value specific energy?
  2. 2. Open channel, with bed slope >02211 AuAuQ Head lossReference line𝑦1 + 𝑧1 +𝑢122𝑔= 𝑦2 + 𝑧2 +𝑢222𝑔+ ∆𝐻1−24
  3. 3. Manning’s formula𝑉 =𝑅23 ∙ 𝑆𝑓12𝑛𝑉 = Mean Fluid Velocity [m/s]R = Hydraulic Radius [m]𝑆𝑓 = Slope Total head [1]𝐴 = Wetted Area [m2]𝑃 = Wetter Perimeter [m]𝑛 = Mannings roughness coefficient [s/m1/3]6
  4. 4. Exercise 2Clean and straight natural channelBed slope = 0 (horizontal), Length = 1000 m,Water level downstream = +1,0 m N.A.P. ,water depth downstream = 0,70 m.Q = 1,5 m3/s, Assuming steady flow1. Calculate water level upstream using Manning, ,assume n = 0,02 s/m1/32. Calculate the mean boundary shear stress3. Is the flow turbulent?4. Uniform or non-uniform flow?5. Value specific energy?
  5. 5. u1Reference [m]Surfacelevel y +z [m]Total Head H [m]P1z1y1u12/2gP2z2y2u22/2gu2212222211122 HguzyguzyHead loss [m]ΔHVelocity Head [m]Open channel, with bed slope <= 04
  6. 6. Little errors or inaccuracies with calculation by hand.1. Length between the calculation points.2. Assume that between the calculation points ∆H = ∆y+1,31 m
  7. 7. Model in sobekWaterdepthDistance (m) Sobek (m) By Hand (m)0 0.7 0.7200 0.78 0.81600 0.89 0.941000 0.96 1.01+1 m NAP+1,26 m NAP

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