NSWC/WOL TR 76-155 



predicting fish-kill.* The non-ideal appearance of the injury 

 correlations shown in Figure 3.4.1b and c are no doubt due to the 

 approximate nature of these two damage parameters. That the impulse 

 damage parameter can be used to describe observed injuries for 

 pressure waves of more than 1/2-cycle in duration (Figure 3.4.1b) is 

 clear evidence of its approximate nature. Apparently, for shallow 

 explosion geometries these two damage parameters approximate some 

 unknown "true" damage parameter about equally well. 



Additional work could possibly yield a better damage parameter 

 than either the Impulse Damage Parameter or the Bladder Oscillation 

 Parameter. However such additional work does not seem justified 

 because at present our ability to predict fish-kill is limited by 

 other more critical factors, namely, knowledge of the pressure 

 signature in the presence of surface and bottom effects and knowledge 

 of the fish species/size/density distribution in the vicinity of the 

 explosion. 



Finally, two observations are noted: 



(1) The bladder oscillation solution can be used to define 

 the useful range of the impulse damage parameter. 



(2) For shallow explosion geometries fish-kill computations 

 using the simpler impulse damage parameter can be used to check 

 computations using the computed bladder oscillation parameter. 



*We are also confident (based on unpublished work to date) that the Lovelace 

 Foundation results (Yelverton et al, 1975) can also be described in terms of 

 the bladder oscillation parameter. To do so is not a routine matter, however, 

 since the negative phase pressure and duration at each fish location must be 

 calculated, and an effective bladder radius coefficient, (Ai) /L (analogous to 

 Equations 3.1.7 and 3.1.8), must be determined by trial-and-error calculations 

 for each fish. 



52 



