Partially Full Pipe Flow Calculations 
U.S. Units




II. Calculation of Discharge, Q, and average velocity, V




for pipes more than
half full













Instructions: Enter values in blue boxes. Calculations in yellow





Inputs

















Pipe Diameter, D =



in





Depth of flow, y =



in






(must have y > D/2)

















Full Pipe Manning








roughness, n_{full} =








Channel bottom









slope, S =



ft/ft














Calculations








n/n_{full} =








Partially Full
Manning








roughness, n =



























Pipe
Diameter, D =


ft






Pipe Radius, r =


ft















Circ. Segment
Height, h =


ft















Central
Angle, q =


radians






CrossSect.
Area, A =


ft^{2}















Wetted
Perimeter, P =


ft






Hydraulic
Radius, R =


ft






Discharge, Q =


cfs






Ave.
Velocity, V =


ft/sec














pipe % full
[(A/A_{full})*100%]
=















