NSWC/WOL TR 77-90 



3. CALCULATIONS 



3.1 PRESSURE-TIME INPUTS . The first step in these calculations 

 was to sketch-in average curves for the three sets of pressure-time 

 signatures at the greatest horizontal range (3.66 m) shown in 

 Figure 2.1. These average curves were then approximated either by 

 two successive exponentials or by a square step followed by an 

 exponential, since these simple wave forms could be calculated by 

 the method presented in Reference 1. 



These approximating pressure-time signatures were then 

 scaled up from 8 lb to 1000 lb and 64,000 lb -- the corresponding 



distances and times were increased in the ratio of the linear scale 



1/3 

 factor (or W ' ) and pressures were held constant. The scaled 



approximating pressure-time signatures for the 1000-lb and 64,000-lb 

 test configurations are shown in Figures 3.1.1 and 3.1.2, respec- 

 tively. As in Reference 1 the exponential portions were calculated 

 using two separate exponential segments joined at t = 1 . 8 9 



p = PMAX e"^/® (t < 1.8 9) (3.1.1) 



p = 0.25 PMAXe-^/4-3 ^ ^^ > ^'^ ®) ^""^'^^^ 



The parameter 9 was taken as the time for the measured pressure 

 to drop to 1/e of its peak value, PMAX. 



3.2 REPRESENTATIVE FISH SPECIMENS . The fish selected for this 



study were Striped Bass (or Rockfish) and White Perch. These are 



the fish expected to be present during the 1000-lb tests in the 



Potomac River during April, May, and June, at the Dahlgren test site 



of the Naval Surface Weapons Center. For each species a single 



representative size was selected for this study -- 38-cm fork 



length for Striped Bass, 17-cm for White Perch. In addition, 



calculations were done for 21.5-cm White Perch in order to compare 



kill probabilities calculated for the air burst tests with kill 



probabilities previously calculated for charges detonated underwater 



(Reference 1). Table 3.2.1 summarizes the fish input data for these 

 calculations . 



