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Pipe Transients
Transients Maths

CID Experimental Rig:

CID Experimental Facility

Air Intrusion

The aim of the CID project was to assess the intrusion of contaminants into a water distribution system through hydraulic transients and sustained low pressures.  As a demonstration of the driving force these low pressures have, the following two videos show low pressures sucking air into the system through a 2mm circular orifice.  The low pressures in both these cases were generated by closing a valve downstream of the test section.

Air entrainement from low pressure transient

The entrainment of the air is apparent from the large sucking sound as the  low pressure waves pass the orifice It can also be seen that each succesive wave is of less intensity than the last untill no further intrusion occurs, after which time the valve is re-opened.

Air entrainement from low pressure transient


If a valve closes too quickly or a pump trips the pressure the system in may drop so low that the water in the pipes cavitates. When this occurs the water boils and forms regions of water vapourWhen the pressure rises again these bubbles collapse causing very large pressure spikes, these can be heard in the videos as the large cracks and booms

Cavitation Generation

The cavitation bubbles also cause an appreciable movement in the pipes and the supporting structure

Cavitation Close Booming

Cavitation  Close

Pipe Shaking with a cracking transient

Pipe Shaking2 with a booming transient

Transients Maths

Maintained and updated by Sam Fox and Richard Collins, June 2015