NSWC/WOL TR 76-155 



APPENDIX E 

 NOTE ON FISH CLOSE TO THE WATER SURFACE 



According to the bladder oscillation model for explosion 

 injury, as the fishes' depth tends to zero near the water surface 

 the kill probability should also tend to zero reqardless of how high 

 the incident pressure. Eventually, however, for fish at the water 

 surface and sufficiently close to the charge, the bladder oscillation 

 model must break down and a different mechanism for injury must take 

 over. Apparently, this happens so close to the charge, and to the 

 water surface, to be of little practical importance, since results 

 reported by the Lovelace Foundation show no evidence of such a 

 transition for 149 gm Carp (length = 21 cm) at a depth of 5 cm 

 subjected to 5.58 megapascals (810 psi) incident pressure. 



A possible close-in non-bladder injurv mechanism is tissue 

 damage due directly to compression by the incident Shockwave. If 

 this is the case, tissue damage probably also occurs due to the 

 pressure wave (generally an order of magnitude areater) emitted by 

 the oscillating swim bladder. Assuming that this is the meaning of 

 the ratio, AMIN/A., in the damage parameter Z, we rewrite Equation 

 3.1.3 in terms of the adiabatic compression ratio, PMIN/p , as 



__1 

 /pmtn\ 



X 



= _ 100 m (^_ N ) 3Y (ei) 



where PMIN is the maximum value of the oscillating bladder pressure 

 (corresponding to radius AMIN at the first compression) , p^ is the 

 initial ambient pressure, and y, the adiabatic exponent for air. 

 Using El we then rewrite 3.1.5 as 



E-l 



