WATER HAMMER 



233 



1 -T- V v seconds after the latter is closed, the conditions are the same as 

 at the beginning of the cycle and the whole is repeated. 



Under such ideal conditions the state of affairs behind the valve, as 

 regards pressure, would be represented by such a diagram as Fig. 106 A, 

 the cycle, in the case of an elastic, non-viscous fluid, being repeated 







Aim OS: 



Press, 



Instant of Va.it e Closing. 



FIG 106. 



indefinitely. At any other point in the pipe, at a distance /i from the 

 open end, the pressure-time diagram would appear as in Fig. 106 B. 



Actually, because of the elasticity of the pipe walls and joints, part of 

 the kinetic energy of the moving column is expended in stretching these, 

 with a resultant reduction in the maximum pressure attained, this 

 reduction depending entirely on the form, material, and construction of 

 the pipe line. Obviously an air vessel or any such device near the closed 

 end will considerably reduce the pressure, and its action may be 

 considered as being due either to a reduction in the effective modulus of 



