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THE COMPUTER SOFTWARE FOR COMPUTATION HEAD LOSSES IN

SEWER SYSTEMS ACCORDING TO PRANTL-KOLBRUK'S FORMULA

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, expressed as:

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.

For computing the value of maximum velocity and the value of maximum flow in soil pipes,

necessary is enter next attributes of pipes in indicated gauge units .

Enter the longitudinal pipes slope - I(‰)

Enter the pipes diameter - D (mm)

Enter the roughness coefficient of pipes (1mm or 1.5 mm) - K (mm)

Enter number of decimal places for determining values of velocity and flow

Maximum velocity of flow through pipes - v_max (m/s)

Maximum flow of water through pipes - Q_max (l/s)

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/Q_max	Degree of pipes filling h/h_max
Relation Q/Q_max	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
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/v_max	Degree of pipes filling h /h_max
Relation v/v_max	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9	1.0
N. F. Fedorov	0.340	0.550	0.710	0.835	0.920	0.980	1.030	1.040	1.034	1.000

For computing the value of maximum velocity and the value of maximum flow in soil pipes,

necessary is enter next attributes of pipes in indicated gauge units .

Enter the real flow in pipes - Q_r (l/s)

Enter the maximum flow in pipes - Q_max (l/s)

Enter the pipes diametar - D (mm)

Enter the maximum velocity of flow in pipes - v_max (m/s)

Enter number of decimal places for determining the real elevation

Relation of flows in pipes   - Q_r/Q_max  (-)

Relation of pipes filling - h_r/h_max (-)

Real elevation of pipes filling - h_r (m)

Relation of velocities in pipes - v_r/v_max (-)

Real velocity in pipes - v_r (m)