Calculating Flow Via Circle Functions

One possible way to calculate flow is to use the CIRCLE function. The CIRCLE function returns the cross-sectional area of the flow in square-units of whatever the depth channel is measured in.

So, assuming the depth channel is in meters, using the CIRCLE function will give square-meters for an output.


  • Assuming the pipe diameter is 0.3 meters, (D) is depth in meters, (V) velocity in meters/second (m/s).
  • The equation for flow in Liters/second (l/s) would be: CIRCLE(D,0.3)*V*1000.
    • This equation produces a flow value in liters per second, the multiplication by 1000 is used to convert cubic meters per second (m3/s), to l/s.
  • If depth is in Millimeters (mm), then the CIRCLE function will give square-mm.
    • To convert back to Square Meters would require function: CIRCLE(D,300)/1000000*V*1000.
    • This equation produces flow in l/s, where the 1000000 value converts from square millimeters (mm2) to square meters (m2), and the 1000 converts  the cubic meters per second (m3/s) to liters per second (l/s).

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