NSWC/WOL TR 76-155 



DYNAMICAL MODEL FOR EXPLOSION INJURY TO FISH 



1 INTRODUCTION AND SUMMARY 



This report describes a method for calculating the kill probability 

 for bladder fish subjected to an underwater explosion. The method 

 consists of an approximate calculation for the extreme values of com- 

 pression and extension of the fishes' gas-filled swim bladder in 

 response to the explosion pressure wave. The calculations are made 

 for the damped radial oscillations of a spherical air bubble in water. 

 The kill probability is then calculated as an experimentally determined 

 function of the ratio of maximum to minimum radius during the oscilla- 

 tory response. For each species of fish the effective swim bladder 

 radius needed for the calculations is determined by trial and error 

 thru correlating the observed injuries with the calculated ratio of 

 maximum to minimum radius. 



The method is used to describe dissection results from 1500 Spot 

 and White Perch caged at depths from 5 to 100 feet and subjected to 

 pentolite explosions of from 1 to 70 lbs submerged at depths ranging 

 from from 5 to 70 feet. 1 ' 2 



These results are then used to calculate several examples of 

 kill-probability and fish-kill distributions for a particular 

 explosion geometry and several species and sizes of fish. Details 

 of the computations are given in the appendices. Appendix C gives 

 an approximate method for calculating the pressure signature from an 

 underwater explosion subject to surface effects including cavitation. 



1. Gaspin, Joel B., "Experimental Investigations of the Effects of Underwater 

 Explosions on Swim Bladder Fish, I: 1973 Chesapeake Bay Tests", NSWC/WOL TR 75-58, 

 1975. 



2. Gaspin, J. B., Wiley, M. L., and Peters, G. B., "Experimental Investigations of 

 the Effects of Underwater Explosions on Swim Bladder Fish, II: 1975 Chesapeake Bay 

 Tests", NSWC/WOL TR 76-61, 19 76. 



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