Analytical and experimental effort explores possibility of using charged particles as diagnostic tool in study of fluid flows. Test program involved right circular cylinder and airfoil located in large wind tunnel; ions were injected into flow and resulting currents at surfaces were monitored

Deluca, M.

Velkoff, H. R.

English

NASA Technical Reports Server

Febhiary 1975	 B75-10028 
NASA TECH BRIEF 
Ames Research Center	
£ 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
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be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Study of Fluid Flow by Charged Particles 
S
An analytical and experimental effort has been 
undertaken to explore the possibility of using charged 
particles as a diagnostic tool in the study of fluid 
flows. Because the results of prior studies had indi-
cated that secondary vortices can be predicted by ion 
measurements, there was ample reason to believe 
that the technique could be extended to include large-
scale external flows around typical aerodynamic 
shapes. The test program involved a right circular 
cylinder and an airfoil located in a large wind tunnel; 
ions were injected into the flow and the resulting 
currents at the surfaces were monitored. The main 
effort of the program involved measurements of up-
stream motion and the nonsteady effects resulting 
from a nonsteady lateral force that was in phase with 
the Strouhal shedding frequency. 
In the experimental work, ions were generated by 
corona discharge from a point or line source, or 
charges were obtained from the dust or water par-
ticles normally in ambient air. The charges were col-
lected and measured as currents at selected positions 
downstream on the particular aerodynamic. shape 
under study. Experimental data indicate periodic 
oscillations in the ion currents, as measured at the 
forward side of the cylinder in crossflow, correspond-
ing to the Strouhal shedding frequency which is 
characteristic of the cylinder and the Reynolds num-
ber. In the aft portion of the cylinder, the oscillations 
were found to be nonperiodic, which would be char-
acteristic of a large-scale, turbulent, separated flow. 
Qualitative analysis of the data verifies the de-
pendence of the ion currents (measured at the cylin-
der) on the vortex shedding frequency (or Strouhal 
number) that is characteristic of flow about a circular 
cylinder. In the tests conducted, this dependence is 
attributed to the fact that the fluid motions are suf-
ficiently slow to permit ions to follow the fluid. For 
a period of vortex shedding that is small with respect 
to the time of ion traverse, the trajectories tend to 
vary less with fluid motion and, thus, flow measure-
ment with ions becomes less useful; in this study, 
such action occurred only under conditions of artifi-
cially high Strouhal number. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: TSP 75-10028 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Michael Deluca of 
Ohio State University
under contract to
Ames Research Center
with Henry R. Velkoff, Ames Research Center 
and U.S. Army Air Mobility R & D Laboratory 
(ARC-10925) 
Category u3 
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 owned rights.
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Study of fluid flow by charged particles

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