NSWC/WOL TR 77-90 



4.3 NOMINAL FISH KILL . In order to assess the fish-killing 

 potential of an explosion we define a "Nominal Fish Kill" based on 

 an assumed uniform fish density distribution of 10 fish of specific 

 species and size per cubic meter of water. Thus, to calculate the 

 Nominal Fish Kill we compute the /p dv where p is the calculated kill 

 probability and multiply by the assumed uniform fish density, i.e.. 



Nominal Fish Kill = lO""^ /p dv (4.3.1) 



where v is the water volume in meters. 



We now wish to calculate the Nominal Fish Kill for the four 

 explosion test geometries described by Figures 4.2.1 and 4.2.2. 

 To do this we approximate /p dv (Equation 4,3.1) by the volume of 

 water enclosed by the 50%-kill contour.* Table 4.3.1 lists the 

 calculated water volumes enclosed by the 50% and 10% kill contours 

 for the four explosion geometries. The calculated volumes for the 

 underwater explosions were used to estimate an average value of the 

 volume ratio, 50%-to-10% kill, (= 33|%) which we then used to esti- 

 mate the 50% kill volume for the full scale air burst test (Figure 

 4.2.2) . 



The Nominal Fish Kill values calculated from these 50% kill 

 volumes (Table 4.3.1, first column) are listed in Table 4.3.2.** 

 The final column of Table 4.3.2 lists the Nominal Fish Kill per 

 kilogram of explosive used. Thus, on a fish/kg basis the underwater 

 shots are some 1000 times more effective in killing fish than the 

 air burst test configurations. 



*This approximation underestimates Jp dv. For the example worked out in Table 

 4.3.1 of Reference 1 (same set of calculations as used here for the 32 kg under- 

 water explosion) this approximation results in a value for Nomina] Fish Kill 

 which is 89% of the value obtained thru the approximate integration described 

 by the Table. For the underwater explosions, volumes enclosed by the contours 

 were calculated by summing cone frustrum elements which approximated successive 

 slices of the figure of revolution. 



**Alternatively, x^?e could describe the fish killing potential in terms of a Mean 

 Kill Volume = Jp dv. (See Appendix A.) Thus, the Nominal Fish Kill is simply the 

 Mean Kill Volume expressed in thousands of cubic meters of water. 



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