10 



EXPERIMENTATION 



The experimental study consisted of measuring the terminal velocity of individual bub- 

 bles of various sizes rising in eight liquids. It also included the determination of the effect 

 of the walls of the container on the bubble velocity. The experimental apparatus consisted 

 of test tanks, means for determining the physical properties of the liquids, a regulated bubble 

 supply, and means for measuring bubble size and velocity. Details of the experimental appa- 

 ratus and procedure, the generation of the bubbles, and the test liquids are given in the fol- 

 lowing paragraphs. 



TEST TANKS 



In order to obtain free bubble rise and to reduce the effects of such boundaries as the 

 bottom of the tank and the free liquid surface, the containers for the liquids had to be at 

 least 2 ft high. The tests were performed in three transparent wall tanks; the large one was 

 of 3 x 3 ft cross section and 5 ft height, the medium one was of 1 x 1 ft cross section and 

 3 1/2 ft height, and the small one was of 6 x 6 in. cross section and 2 ft height. In addition, 

 tests were also performed in an insert of 6 x 6 in. cross section and 20 in. height, placed in 

 the center of the medium tank. 



Since the large tank was of sufficiently large dimensions, no significant wall effect 

 was expected. The dimensions of the medium tank were chosen large enough to reduce wall 

 effects, yet small enough to allow use of a variety of liquids. The small tank and the insert 

 provided an additional tank size. It was intended that if wall effect existed, the results ob- 

 tained in the finite containers would be extrapolated to the case of an infinite medium. 



TEST LIQUIDS 



The eight test liquids used were water (at three different temperatures), Varsol, 

 methyl alcohol, turpentine, water containing 0.42 percent (by volume) Glim, mineral oil, 

 and two corn syrup-water mixtures. Turpentine was selected as one of the test liquids be- 

 cause at room temperature it has the same viscosity as cold water. One of the corn syrup 

 mixtures had approximately the same viscosity as the mineral oil (see Table 1). 



The viscosity of the liquids was measured by means of ordinary and modified Ostwald 

 viscosimeters. The accuracy of measurement of viscosity was 1.5 percent and 0.5 percent, 



*A few of the previous Taylor Model Basin tests were repeated in the large tank to observe any change in 

 results. These previous tests were conducted in a tank of 4 1/2 X 25 ft cross section and 9 ft height with 8 ft 

 depth of filtered water at room temperature, using one end of the tank for the tests. 



**A trade name (Standard Oil Company) for mineral spirits (heavy naphtha), a petroleum distillate. 



***Glim (Antarox A-480), a surface-active agent, is the trade name (B.T. Babbitt, Inc.) of a non-ionic, liquid 

 detergent, a condensation product of ethylene oxide and lauryl alcohol. 



