Enter the volumetric flow rate of the liquid through the pipe and the internal pipe diameter into the calculator to determine the pipe velocity.

Pipe Velocity Formula

The following equation is used to calculate the Pipe Velocity.

PV = .408 *  Q / D^2
  • Where PV is the pipe velocity (ft/s)
  • Q is the volumetric flow rate through the pipe (gpm)
  • D is the internal diameter of the pipe (in)

To calculate the pipe velocity, divide the volumetric flow rate by the diameter squared, then multiply by .408.

What is a Pipe Velocity?

Definition:

A pipe velocity describes the linear speed at which a liquid flows through a pipe. The pipe velocity depends on the volumetric flow rate of the liquid and the pipe’s internal diameter.

How to Calculate Pipe Velocity?

Example Problem:

The following example outlines the steps and information needed to calculate Pipe Velocity.

First, determine the volumetric flow rate through the pipe. In this example, the volumetric flow rate through the pipe is found to be 50 gpm.

Next, determine the internal diameter of the pipe. In this case, the internal diameter of the pipe is measured to be 5 in.

Finally, calculate the Pipe Velocity using the formula above:

PV = .408 * Q / D^2

PV = .408 * 50 / 5^2

PV = .816 ft /s

FAQ

What factors can affect pipe velocity besides the internal diameter and volumetric flow rate?

Several factors can influence pipe velocity, including the viscosity of the fluid, the roughness of the pipe’s internal surface, the temperature of the fluid, and any bends, fittings, or obstructions in the pipe that may cause resistance to flow.

How does changing the pipe diameter affect the velocity of the fluid?

According to the continuity equation and the pipe velocity formula, if the volumetric flow rate remains constant, increasing the internal diameter of the pipe will decrease the velocity of the fluid. Conversely, decreasing the internal diameter will increase the fluid’s velocity. This is because the fluid has less space to flow through, requiring it to move faster.

Can the pipe velocity formula be used for any type of fluid?

While the basic formula for calculating pipe velocity (PV = .408 * Q / D^2) is generally applicable, adjustments may be needed for fluids with significantly different properties from water, such as high viscosity oils or gases. The formula assumes a Newtonian fluid with a density and viscosity similar to water. For non-Newtonian fluids or those with very different properties, more complex calculations that account for these differences may be required.