Studies on the Water-Hammer Effect in Cases in which a Certain Amount of Air Exists in Pipe-lines

Abstract

In agriculture, there are times when irrigation is needed and not neeeded.Therefore, due to this fact pipelines used for agriculture have more occurrences of air being entrapped within them than ordinary piping.
When observing the bulk coefficient of elasticity for water and air, one will notice that they have extremely different characteristics.Water is considered to be an incompressible fluid, but on the other hand, air is a typical compressible gas.
As a result, the water-hammer effect occurs differently when air is in the pipeline as opposed to when it is not.
In examining the safety of pipelines, it is important to know that the maximum water-hammer pressure that will occur when air is mixed with water.
Air is often used in controlling the water hammer effect, however, it is said that air has a dangerous influence on the water hammer effect.
But up until now there is no information about exactly what is actually dangerous and how it affects the system.
In this paper, we have taken on the task of study agricultural pipelines that have air entrapped within their systems and have made an all-out effort to solve the problems derived from this phenomenon, so as to reduce the water-hammer effect in piping.
The results obtained are summerized as follows:
1) The method of theoretical estimation for maximum water-hammer pressure in cases where air has been mixed in with the water is stated.A comparison of theoretical and experimental values are shown in Fig.10.
2) Characteristics of maximum water-hammer pressure in relation to the place where the entrapped air and water have been mixed, it's length, air content ratio and the closing time of the valve are shown in Fig.11, 12, 13 and 15.