Basic Hydrology & Hydraulics: DES 601 Module 14 Closed Conduit Flow

Closed Conduits A closed conduit is a conduit (culvert, storm sewer) that has the conduit crown as the upper limit of flow – hence it behaves as a pipe under pressure The HDM uses Manning’s equation as the loss model for closed conduits Module 14

Hydraulic Grade Line (HGL) Total energy line is called energy grade line (EGL) EGL = h + p/g + V2/2g Line that is sum of elevation and pressure energy is called hydraulic grade line (HGL) HGL = h + p/g For pipes flowing full, EGL and HGL are parallel if pipe diameter does not change. The invert elevation is called the flowline in the HDM Module 14

HGL illustration HW = headwater TW = tailwater Module 14

Energy Equation The slope of the energy grade line is the friction slope in Manning’s equation Thus the energy equation for the figure is Module 14