In: Civil Engineering
"Two reservoirs 1200 m apart are connected by a 50-cm smooth concrete pipe. If the two reservoirs have an elevation difference of 5 m, determine the discharge (20 degree C) in the pipe by the Darcy Weisbach equation, (b) the Hazen- Williams equation, (c) the Manning equation. Assume minor losses are negligible and verify your results with computer software."
Distance between reservoir, that is the length of pipe, l = 1200m
Diameter of pipe, Dc = 0.5m (full flow condition is assumed)
head loss, hl = 5m
Discharge, Q, as per Darcy Weisbach equation
S=f*8π2g+Q2Dc5
S à hydraulic slope (hl/l)
f à Darcy friction factor; Re = 2000
f=64Re
f = .032 (for laminar flow)
therefore, substituting in the above equation, Q = 0.00699 m3/s
Computer Analysis Using EPANET
Used two pipes of 600m length and .5m dia for successful analysis. Below is the screenshot of the results as per each equation:
as per Darcy Weisbach equation
as per Hazen- Williams equation
Discharge, Q, as per Hazen- Williams equation
S=10.67*Q1.852C1.852*d14.87045
Cà Roughness coefficient, C = 100.
Q = 0.00159 m3/s
Discharge, Q, as per Manning equation
Q=.312n*D83*S1/2
D = A/P ; S=.5/1200; n = 0.015
Q = 0.00165 m3/s