WATER HAMMER 



239 



about '21 seconds, while when T = '26 seconds, the mean error involved 

 in using the uncorrected formula in this case is about 14 per cent. 



In a series of experiments carried out by M. Joukowsky 1 on cast-iron 

 pipes of 4 inches and 6 inches diameter, having lengths of 1,050 and 

 1,066 feet respectively, the time of valve closing being '03 seconds in each 

 case, the observed rise in pressure agrees closely with the formula, 

 p = 57 v. The following are some of the results obtained by interpolation 

 from the plotted results of these experiments. 



4-iNCH PIPE. 



6-iNCH PIPE. 



The pressure in the last experiment, calculated on the assumption that 

 the water is incompressible, is 3,585 Ibs. per square inch, a result which 

 sufficiently indicates the nature of the errors involved in extreme cases 

 by neglecting the effect of elasticity. 



These sudden increases of pressure, commonly known as water 

 hammer, may evidently become most serious with large values of r, and 

 in such cases the ill effects due to the too sudden closing of a valve 



1 Stoss in Wa*xerleitungtri>hren, St. Petersburg, 1900. The author has been unable to 

 ascertain the thickness of the walls of these pipes. Abstract by O. Simin in Trans. Am. 

 Waterworks Ass., 1904. 



