NSWC/WOL TR 76-155 



l/3\ a 

 PMAX = k (L- (C2) 



(^7 



a. w 



V3 /_R \ P (C3) 



O 3 ) 



where W is the explosive weight of the charge, R is the slant range 

 from the charge, and k, a , £, and 8 are empirical constants (see, 

 e.g., Reference 7). Values for the constants, k, and I and $ used 

 for the calculations of this report can be obtained from Equations 

 3.1.1 and 3.1.3. 



The instantaneous free-field (or direct arrival) pressure, 

 p_, was calculated using two separate exponential segments joined 

 at t = 1.8 



PMAX e" t/G (t < 1.8 0) (C4a) 



P D (t)= j 



0.25 PMAX e" t/4 ' 3 6 (t > 1.8 0) (C4b) 



which were fitted to the pressure signatures recorded on the 1973 

 explosion test series. 



CALCULATION OF PNEG, NEGATIVE PRESSURE FOLLOWING SURFACE 

 CUT-OFF . PNEG was determined by a calculation along the surface 

 reflected ray from the charge to the fish. If the surface reflected 

 ray went thru the region of bulk cavitation, PNEG was computed from 

 the depths at which the ray intersected the top and bottom of the 

 cavitation. Otherwise, PNEG was computed from the linear super- 

 position of the direct and surface-reflected pressure waves. 



C-3 



