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The head losses in sewer systems can be computed by the Prandtl-Colebrook's
formula, expressed as:
where: Re is the Reynolds number, l is the friction coefficient, D is the inside pipe diametar (m),
K is the roughness coefficient (m)
The critical value of Reynolds number Re
is computed by the next formula:
By combine the Prandtl-Colebrook's formula and Chezy's formulas provides formula for the maximum velocity
in sewers system with circular section,
where: v is the maximum velocity (m/s) and g is gravitational acceleration (m/s”)
we obtain the value of maximum velocity and
the value of maximum flow through a pipe.
Pipes in sewerages are mostly not full up and because of that we have to compute values
of velocity and flow in partially filled profile.
Water elevation's dependence on flow in pipes is represented at table 1.
|Relation Q/Qmax||Degree of pipes filling h/hmax|
|N. F. Fedorov||0.020||0.073||0.175||0.311||0.468||0.628||0.765||0.890||0.975||1.000|
Velocity's dependence on water elevation in pipes is represented at table 2.
|Relation v/vmax||Degree of pipes filling h /hmax|
|N. F. Fedorov||0.340||0.550||0.710||0.835||0.920||0.980||1.030||1.040||1.034||1.000|