SUMMARY 



It does not appear possible to place electrodes using the earth's field to 

 produce such a rejection filter. Perhaps another configuration employing ac fields 

 could be constructed to give average velocity readings over lai'ge distances. 



The main advantages of the induction method are the lack of moving parts; 

 high-frequency response; linear output; and direction-sensing ability. The major 

 disadvantage with the tube-type meter using its own ac magnetic field is a probable 

 noncosine direction response. The principal disadvantages with the earth's field 

 method are the low signal levels and zeroing problems. Installation and proper 

 maintenance would also be a problem. Direction response is a cosine function, 

 and the rejection-filter configuration should be kept in mind. 



Drag Force 



STEADY-STATE FLOW 



This method consists of recording the hydrodynamic drag on a fixed object, 

 which for convenience is usually attached to a stiff suspension system. The small 

 relative motion between the object and the mounting can be measured and recorded. 

 The shape and size of the object and the suspension are design variables. 



For the steady-state flow in the region of interest here, the drag can be 

 given by 



D = l/2rCD ApU\U\) 



where 



D = drag force 



Cg = drag coefficient 



A = cross-sectional ai'ea of object perpendicular to flow 



p = fluid density 



U = velocity of object relative to fluid 



The steady-state drag coefficient Cg for a given shape is determined 

 experimentally as a function of the nondimensional Reynolds number. The Rey- 

 nolds number, R, is given by 



(21) 



R = 



pU d U d 



(22) 



23 



