Obtain measurement of the head (H). This is the height at which the water is raised to at the discharge of the jet pump. Measure the head as distance from the water surface of your tank or well to the discharge pipe end (nozzle). Make sure all your measurements are in the same standard unit. Know that 1 foot equals 0.3048 meters.
Find the friction coefficient of the nozzle (C), coefficient of discharge, from the supplier of the jet pump. If it is not provided, assume a general average of C = 0.95.
Use the Bernoulli Equation to calculate drive flow velocity:
V = C * square root (2*g*H); where g is acceleration due to gravity and equals 9.8 m/s
Substitute C and H (in meters) with your numbers into the formula to find velocity in meters per second.
Find the drive flow velocity of the jet pump if the head of water at the nozzle equals 80 meters and the friction coefficient C equals 0.95.
Calculate velocity using the Bernoulli Equation from Step 3:
V = 0.95 * square root (2 * 9.8 m/s * 80 m) = 0.95 * 39.6 = 37.6 m/s
The drive flow velocity of this jet pump is 37.6 meters per second.