Water Hammer Theory Explained

When a there is a sudden or instantaneous change of flow in a pipe this causes water hammer. Usually this occurs when a valve such as a tap or faucet closes quickly. Water hammer can generate very high transient pressures which could burst a pipe and can generate pipeline vibrations. In this video the process of water hammer is explained and you are shown how to calculate the pressure rise using the Joukowsky equation. The video also proves the Joukowsky equation from first principles. To use the Joukowsky equation you need to know the fluid density, fluid velocity and sonic wave speed in the pipeline. The video shows how to use Hookes law to calculate the wave speed and how this formula is modified to take into account the pipeline wall thickness and young’s modulus.
The video gives an example of how to calculate the surge pressures and wave speed for a 15mm cooper pipe.
Water hammer is part of the larger subject of transient flow or surge analysis. Water hammer is the special case when the flow is stop very rapidly or instantaneously.
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Fluid Mechanics are consultant hydraulic engineers who can analyse and design for surge and water hammer in pipelines.