What phenomenon occurs when a nozzle is closed quickly and suddenly?

When a nozzle is closed quickly and suddenly, the phenomenon that occurs is known as Water Hammer. This effect is primarily due to the abrupt change in water flow. When the flow of water is rapidly halted, the momentum of the moving water creates a shock wave or pressure surge within the plumbing system. This sudden pressure change can lead to damaging vibrations and sounds, akin to a hammer striking a surface, hence the name "Water Hammer."

Understanding this phenomenon is crucial in fire suppression systems, where sudden changes in water flow can affect the integrity of the piping and nozzle components. Properly designed systems often incorporate features to mitigate the effects of Water Hammer, ensuring smooth operation and reducing the risk of damage to equipment.