Simple, inexpensive drag sphere velocity meter with a zero to 6 ft/sec range measures steady-state flow. When combined with appropriate data acquisition system, it is suited to applications where large numbers of simultaneous measurements are needed for current mapping or velocity profile determination

Roberts, C. W.

Smith, D. L.

English

NASA Technical Reports Server

g Sphere 
Gages 
Electrical 
Leads
December 1970	 Brief 70-10662 
S	 NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the National Technical Information Service, Springfield, 
Virginia 22151. Requests for individual copies or questions relating to the Tech Brief progam may be directed to the Tech-
nology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Water Velocity Meter 
A water current meter with a 0 to 6 ft/sec range has 
been developed for steady-state flow measurements. 
Two mutually perpendicular components of the drag 
force exerted on a perforated sphere (see -fig.) are 
measured via strain-gage techniques similar to those 
applied in wind tunnel instrumentation. This force is
	 Force 
then related to the flow velocity about the sphere as 
follows: 
F =/F 2 + F2 where F = drag force X	 y	 0 = flow direction 
.	 0 = tan	 p fluid density 
Fy	 A = frontal area of drag sphere 
V
	
	 "2F	 C D = drag coefficient 
p ACD 
The velocity range of from 0 to 6 ft/sec corresponds 
to a force range on the order from 0 to 1.7 lb. 
These drag sphere velocity meters are simple and 
relatively inexpensive; and, when combined with an 
appropriate data acquisition system, they are well 
suited to applications where a large number of simul-
taneous measurements are needed for current mapping 
or velocity profile determination. 
Note:	 Patent status: 
Additional documentation may be obtained from: 	 No patent action is contemplated by NASA. 
Technology Utilization Officer 	 Source: D. L. Smith and C. W. Roberts 
Langley Research Center	 Instrument Research Division 
Hampton, Virginia 23365 	 Langley Research Center 
Reference: TSP70- 10662 	 (LA R-l06l9) 
Category 02 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States	 will be free from privately ownedrights.
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Water velocity meter

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