NSWC/WOL TR 76-155 



IV. CONCLUSIONS 



30. I hope that the analysis presented here (or some 

 further development of it) will prove useful in correlating observed 

 fish injury and kill with incident explosion pressure signatures. 

 The present analysis is but a crude first cut, however; and if 

 this approach to understanding fish damage should appear fruitful, 

 considerable further development will probably be desirable and 

 perhaps essential to achieving a useful correlation. Nevertheless, 

 some things are already clear. For example: 



(1) By itself, a step increase in the ambient pressure 

 cannot extend the bubble/bladder beyond its original size, since the 

 bubble oscillates between its original volume and some minimum volume 

 which depends on the magnitude of the incident shock pressure. 

 Extensions beyond the initial at-rest volume can only occur after 

 return to ambient pressure or below. 



(2) For a simple positive step pressure which returns to 

 the ambient level, the maximum bubble/bladder extension depends on 

 both the magnitude and duration of the pressure pulse. If cut-off 

 occurs at the instant of maximum bubble volume, the bubble is 

 returned to its initial at-rest state, having undergone no extension 

 beyond this initial at-rest state . If cut-off occurs at any other 

 time, some extension beyond the initial at-rest volume occurs. For 

 a given incident pressure level, the greatest bubble/bladder 

 extensions occur when cut-off is at the instant of minimum bubble 

 volume. * 



* Footnote next page 



A-22 



