Introduction to Fluid Mechanics

Pipe Flow Networks

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The pressure at a point in a fluid is called the 'static pressure'. The 'stagnation pressure' is the pressure that the fluid would obtain if brought to rest without loss of mechanical energy. The difference between the two is the 'dynamic pressure'. The 'total pressure' is the sum of the static pressure, the dynamic pressure, and the gravitational potential energy per unit volume. It is therefore the sum of the mechanical energy per unit volume in a fluid.

As fluid flows through a pipe network, the mechanical energy per unit volume (the total pressure) reduces due to irreversible processes, such as viscous dissipation. This clip shows how the total pressure drop across an orifice plate is calculated

This clip shows how the total pressure loss along a pipe is calculated.

This clip shows how the total pressure loss at a sudden expansion is calculated. (The full derivation, in text form, is at the end of the chapter.)

This clip shows how to deal with a wall along one side of a control volume

The total pressure loss across general pipe components is tabulated in books or embedded within pipe network software

Pumps do shaft work on a fluid, while turbines extract shaft work. The power in or out of this process is the total pressure change multiplied by the volumetric flowrate. (This is only valid for uniform density flows; in compressible flows, the internal energy must also be considered and the steady flow energy equation should be used.)

This clip shows how to work out the required mechanical power of a pump in a pipe network.

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