This study aims to evaluate the energy loss at manhole. Experimental model with straight pipes (D=0.2 m for diameter, 18.5 m for length) and four rectangle-shaped manholes (0.26 m for width, Dm=0.12 m for length) was used. Energy losses at manholes, Δ H, were determined as the difference of hydraulic gradient lines at the center of the manhole extended from both upper and lower side of pipes. The energy loss coefficient was given as K=(Δ H)(2g)/v2. Obtained coefficients converged their range from 0.02-0.12 to 0.04-0.06, according to the increase of the water velocity. We concluded that the reason of this comparatively smaller K values was due to the smaller diameter ratio; Dm (manhole diameter or length)/D(pipe diameter), compared to the results of other experiments.

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