WATER HAMMER 229 



accordance with those calculated from this formula. In Fig. 103 the 



Valve c/osed\ 



Valve begins to close 



A tmospheric _} 



90 ^ 

 u 



w % 



70 *. 



50 



w Open 



30* * 



1L0 Pressure 



Time T Seconds 

 FIG. 104. 



experimental results are plotted against the dotted curves which represent 



the calculated results. 



Series A. a -=- ai = 19'5 h = 104'6 ft. 



B. = 34-7 = 104-6 



C. = 72-5 = 105-5 



D- = 8-6 = 104-0 



Pressures were measured by an indicator whose drum received its 



rotary motion directly 



from the spindle of the s/uare 



valve, and a typical 'Jj}F h ' 



diagram under these 3(j 



conditions is shown in 



Fig. 104. 



When the valve has to 



reached its seat the 



pressure falls below that 



corresponding to the 



statical head, then rises 



again, a wave of pres- 

 sure being reflected backwards and forwards along the pipe. This portion 



of the phenomenon, due solely to the elasticity of the water column, will 



