12 



-E> 



Camera 



••-Sliding Mechanism 



To Balance 



Air Supply 



— Glass Funnel 



Insert 



Camera 



Dumping Cup 



Nozzle 



Figure 1 - Experimental Setup 



BUBBLE GENERATION 



Small bubbles were generated by means of hypodermic needles and glass nozzles of 

 various sizes. The larger bubbles were obtained by use of a dumping cup, which was inverted 

 to release the air bubble. The nozzles and needles were connected to a brass tube which 

 was fastened to a sliding mechanism (Figure 1). This sliding mechanism allowed the tips of 

 the various nozzles to be placed at the identical position. The air was supplied from a com- 

 pressed air bottle. A needle valve regulated the air flow so that bubbles were released at the 

 interval desired. 



DETERMINATION OF BUBBLE SIZE 



The bubble size was determined by "weighing" a sufficient number of bubbles in the 

 inverted funnel (Figure 1) by means of an analytical balance. Since the density of air is 

 negligible in comparison to that of a liquid, the difference in balance reading equals the 



♦This device eliminated focusing of the camera after each change of nozzle. The camera was used to deter- 

 mine velocity, path, and shape of the bubble. 



