be made to show the fluid velocity patterns clearly on film will siof f ice , 

 At some indicative value of the total pressure^ the coulomb transfer across 

 the surface area of the wetted wire can then be determined. In the time 

 interval of the pulse width;, this coulomb transfer specifies the required 

 current. This current is expressed by: 



T - eA (p + Y h) L d^TT 



ITr WT 

 u 



where 



I is the current, 



e is the charge of an electron, 



A is Avogodro's number, 



p is the pressure at the water surface, 



Y is the specific weight of the water, 



h is the depth of the platinum wire, 



d is the width of the hydrogen bubble row, 



L is the length of the hydrogen bubble row, 



R is the Universal Gas Constant, 

 u ' 



W is the pulse width, and 

 T is the temperature . 



Now the power per pulse can be specified and the electrical equipment output 

 determined when line losses are incorporated into the above result. 



The hydrogen bubbles observed in the work reported here were produced 

 by several different power supplies . The dc power supply which was used to 

 excite the kinked wire (DTMB unit, Type lUOA, Serial 101 ) transmitted a 

 maximum of I50 V and 5OO ma to the wetted wire. A continuously variable 

 voltage amplitude was available by means of this dc power supply. The 

 insertion of a suitable switch in the output of this power supply permitted 

 a polarity reversal which was very helpful in keeping the wetted wire free 

 from platinum oxides. 



In addition to the dc power supply, a Hewlett-Packard Model 21UA 

 Pulse Generator was used for the pulsed power supply. This unit delivered 

 - 170 V into the approximately 300-ohm load resistance and produced 

 excellent bubble rows for flow velocities up to about 5 ft/sec. The output 



li^ 



