Simple Flow Calculations 

Open Channel Flow  Velocity Flow 


Nearly all flow measurement systems, techniques and calculations –

“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”. 

The basic equation for most flow measurement applications is: Q = V A
Where: Q = Flow rate e.g. m^{3}/s V = Velocity e.g. m/s A = Area e.g. m^{3}/s 

“An Open Channel is any pipe or conduit where the water surface is at atmospheric pressure”  
The term “Velocity Area” usually refers to measuring flow in an open channel or partly filled pipe where the flow velocity and cross sectional area are measured separately. In a channel with a regular cross section, the area is usually obtained by measuring the depth of flow (the head)
The simplest method of measuring flow in an open channel is to measure the depth of flow and calculate the cross sectional area and then to estimate the velocity by throwing a stick or other floating object into the flow stream and measuring the time it takes to travel a set distance! It is not a very sophisticated technique but can often be a first step before deciding on more sophisticated systems. 

The following flow calculations are available free of charge:
Open channel Slope Area Method (Manning Equation)

