PIPE FILL CALCULATOR FULL
If the pipe slope and Manning roughness coefficient are known, then it should be easy to calculate flow rate and velocity for the given depth of flow using the Manning Equation, right? No, wrong! As long ago as the middle of the twentieth century, it had been observed that measured flow rates in partially full pipe flow aren’t the same as those calculated as just described. Using the geometric/trigonometric equations discussed in the next couple of sections, it is relatively easy to calculate the cross-sectional area, wetted perimeter, and hydraulic radius for partially full pipe flow with any specified pipe diameter and depth of flow. Is the Manning Roughness Coefficient Variable for Partially Full Pipe Flow Calculations? The calculations are complicated a bit by the need to consider the Manning roughness coefficient to be variable with depth of flow as discussed in the next section. With the use of Excel formulas in an Excel spreadsheet, however, the rather inconvenient equations for area and wetted perimeter in partially full pipe flow become much easier to work with. Q full and V full can be conveniently calculated using the Manning equation, because the hydraulic radius for a circular pipe flowing full is simply D/4. The parameters, Q and V in this graph are flow rate an velocity at a flow depth of y in a pipe of diameter D. As a result graphs of Q/Q full and V/V full vs y/D, like the one shown at the left are commonly used for partially full pipe flow calculations. There is no simple equation for hydraulic radius as a function of flow depth and pipe diameter. the Manning equation applies if the flow is uniform flow For background on the Manning equation and open channel flow and the conditions for uniform flow, see the article, “ Manning Equation/Open Channel Flow Calculations with Excel Spreadsheets.”ĭirect use of the Manning equation as a partially full pipe flow calculator, isn’t easy, however, because of the rather complicated set of equations for the area of flow and wetted perimeter for partially full pipe flow.
The Manning equation can be used for flow in a pipe that is partially full, because the flow will be due to gravity rather than pressure. Read on for information about Excel spreadsheets that can be used as a partially full pipe flow calculator. To obtain Excel spreadsheets for partially full pipe flow calculations, click here to visit our spreadsheet store for partially full pipe flow calculator spreadsheets. Where to Find Partially Full Pipe Flow Calculator Spreadsheets
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