409 



Figure T 7 - Curves and Formulas for Estimating Roughly the 

 Effect of Migration on the Pressure in the Water 



r„ is the maximum pressure in the water at the instant of greatest recompression of the gas globe 

 in pounds per square inch, p„ is the total hydrostatic pressure in pounds per square inch and p. 

 is tiie same pressure expressed in atmospheres, Iq 2 is the peak impulse defined as /pdt integrated 

 between points before and after the peak at which p„, - Pg is one-fifth of its value at the peak, 

 r denotes distance in feet from the center of the gas globe at the instant of maximum recompres- 

 sion, Kg is the first maximum radius of the gas globe in feet, Q is the linear displacement of 

 the gas globe from the point of detonation iintil the instant of greatest recompression, in feet. 



to all migratory cases can be constructed, therefore, by plotting against 

 Q/R2 values of 



p„r r I 



where p^ is the total hydrostatic pressure p^ measured in atmospheres and p^ 

 is the maximum excess of pressure above p^. This is done in Figure ^'J. The 

 impulse /„ 2 is taken between the two instants at which the excess of pres- 

 sure p - Pq is 1/5 of its intervening maximum value. The values of /„ 2 thus 

 serve to give an idea of the estimated width of the pressure peak. 



To use Figure 17. the value of the displacement Q is first estl- 

 jmated by use of formulas given previously; then values of y and 2 are read 

 off the curves and p„ and /^ 2 3^® calculated from the formulas 



«■; 



Pm~Po ^ r Py^y pounds per square inch 



[56a] 



