Originally Posted by Unregistered
if i wanted to convert say 30 gallons per minute going through 3/4" tube how could i convert this to knots
Fundamentally you divide the volumetric flow rate by the cross-sectional area to get velocity, but you also have many incompatible units to reconcile. Since a knot is defined as 1.852 km/h, we need to convert to metric units, and it helps to use hours in the flow rate.
30 gallons per minute is 1800 gallons per hour. A gallon is 0.0003785411784 m³, or 6.814 m³/h, rounding the result to sensible precision
The area is pi*r² = 3.14159 x (0.375 in x .0254 m/in)² = 6.1818 x 10^-4 m²
Dividing, the velocity is 11022.7 m/h, 11.0227 km/h, or 5.95 knots.