NSWC/WOL TR 76-15 5 



II. ON THE MOTION OF A SWIM-BLADDER-SIZE AIR BUBBLE SUBJECTED 

 TO AN EXPLOSION GENERATED PRESSURE WAVE 



22. At the present time we ask such questions as: "Can 

 a nearby explosion kill or seriously damage fish by extending their 

 swim bladders?" Prodded by this, let us calculate the behavior of 



a bladder-sized air bubble subjected to an explosion pressure 

 signature — one which kills many, but not all, of the fish present. 

 The pressure signature shown in Figure A-2 is derived from a experi- 

 mental test condition (Shot 525, Chesapeake Bay Tests, July-Aug 73) 

 and appears to meet this criterion. It corresponds to a fish cage 

 location where, upon subsequent dissection, all ten of ten 5.4" long 

 Spot and six of ten 7.2" long White Perch were judged to have 

 received lethal damage. For this calculation we will further 

 approximate the outside pressure signature with the square-stepped 

 one which is also shown in Figure A-2. 



23. To get a better feel for physical phenomena, we will 

 do the calculation in three stages. First, we will calculate the 

 response to the positive portion, a square-step which returns to the 

 initial ambient pressure level; then, the response to a simple step 

 decrease in outside pressure to the level of the explosion induced 

 underpressure; and finally, the combined response to the square- 

 stepped signature sketched in Figure A-2. 



24. We will take our bladder-sized air bubble from a 5.4" 

 long Spot, and start the calculation with an initial (at rest) bubble 

 radius given by* 



A j _ = 0.0395 L (A43) 



it 

 Footnote on page A-16 



A-14 



