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Simple Flow Calculations |
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Open Channel Flow - Slope Area |
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What is now called the Slope Area Method of measuring flow in an open channel was originally developed by Robert Manning in the late 19th century.
Manning presented a formula to determine the velocity of the flow which was based on the hydraulic gradient and the roughness of the pipe or channel.
For simple calculations the hydraulic gradient can be taken as the gradient of the channel. Tables of n values are available for different pipe and channel materials |
“The rate of flow of a liquid moving in a pipe or an open channel is dependent on the velocity and the cross sectional area of the liquid”. |
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The basic equation for most flow measurement applications is:- Q = V A
Where:- Q = Flow rate e.g. m3/s V = Velocity e.g. m/s A = Area e.g. m3/s |
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| “An Open Channel is any pipe or conduit where the water surface is at atmospheric pressure” | |||||||||||||
The accuracy of the Slope Area Method depends on:-
1) A uniform flow pattern – a straight section of channel without bends is required. 2) Accurate determination of the n value 3) Accurate measurement of the cross sectional area. |
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The following flow calculations are available free of charge:-
Open channel Velocity Area Calculation
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