SUMMARY 



The hydrogen-bubble visualization technique has been 

 adapted to the 12- inch variable -pressure water timnel of the 

 David Taylor Model Basin. An outline of this adaption and the 

 operation of the technique; are described. 



Photographic techniques and analyses applied to the result- 

 ing films are discussed. Sources of error are delineated, par- 

 ticularly with regard to the deceptive streakline patterns that 

 can be formed and especially the results of exceeding the velocity 

 limitation imposed by the shedding phenomena taking place behind 

 the platinum wires. Errors caused by compression and/or stretching 

 of bubble lines along their length are discussed, and procedures 

 are given for recognizing this type of error. In addition, cathode- 

 wire configurations are described by which both longitudinal and 

 transverse velocity profiles can be obtained in steady or unsteady 

 water flows . 



Various cathode-wire configurations are described through 

 which qualitative aspects of the flow about bodies as stagnation 

 and separation point motions are depicted. 



INTRODUCTION 



The uses of visualization techniques for the determination of the 

 characteristics of fluid flows have become quite diversified since Reynolds' 

 transition experiments in the l880's. The introduction of visible media 

 into fluid flows has been accomplished in many ways for the acquisition of 

 either qualitative and/or quantitative flow characteristics. Injection of 

 dyes into liquids or smoke into gasses through porous bodies or hypodermic 

 needles, the homogenous mixing of visible "unity oil" - (Sp/Or. = l) in 

 water, the ihypodennic- injection of anlsol bubbles into boundary layers. 



