Nonsteady flow probe uses miniature pressure transducers mounted within probe support very close to tube inlets. Response speed depends on internal volume between tube inlet and pressure transducer location

Krause, L. N.

Summers, R. L.

English

NASA Technical Reports Server

P2 
III_i,__
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July 197	 B72-10403 
67,
NASA TECH BRIEF 
Lewis Research Center	 - 
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 program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Nonsteady Flow-Direction Measurement 
Flow Direction	 Reference 
Transducers	 Pressure Line 
Transducer 
3-Tube Strobe 
A probe has been developed for the measurement of 
flow direction as well as total pressure for nonsteady 
flow. 
One of the quantities usually required in experimental 
fluid mechanics is fluid velocity. In all but the simplest 
experiments, a measurement of steady flow direction is 
required together with measurements of total and static 
pressure. Recent jet engine inlet experiments have re-
quired the measurement of flow direction and total 
pressure for nonsteady flow. 
Flow direction for steady flows is continuously de-
termined by the use of a pressure probe which has 
symmetrically oriented taps that are sensitive to flow 
direction. The probe shown in the figure is a 3-tube 
assembly using two bevelled tubes to sense flow direc-
tion and a central square-ended tube to measure total
pressure. The probe is fixed, and flow direction is 
determined from a correlation based on the relationship 
between probe pressures and flow direction. 
For nonsteady flow, the steady-state flow probe 
described above is modified by using miniature pressure 
transducers mounted within the probe support very 
close to the tube inlets, to shorten response time. The 
speed of response is dependent on the internal volume 
between the tube inlet and the pressure transducer 
location. The graph shows traces of the electrical output 
of the transducers when the probe is immersed in a gas 
stream whose flow direction alternates rapidly from 
+100 to 
Nonsteady flow direction in two planes may be 
obtained by the addition of a pair of bevelled tubes 
perpendicular to those shown.
(continued overleaf) 
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. 
Strut
https://ntrs.nasa.gov/search.jsp?R=19720000402 2020-03-17T03:39:11+00:00Z
(P 1 —P 2 ) For +1O0 
	
(P 1 —P 2 ) = 0	 (P1—P2) For —100 
(P1	 2 ) Trac e 
t Trace	
(Pt—Ps) 
_ 
	
001 Sec	 P5 
Flow Direction And Total Pressure Traces 
	
Typical test data indicate that, within its response 	 Reference: NASA-TM-X-52962 (N71.18632), 
	
capability, the probe measures the nonsteady flow 	 Non-Steady Flow-Direction Generation and 
	
direction to within 0.5 0 , as well as the nonsteady total 	 Measurement. 
pressure.	 3. Technical questions may be directed to: 
Technology Utilization Officer 
Notes:	 Lewis Research Center 
1. Development of such probes to measure nonsteady 	 21000 Brookpark Road 
	
flow direction requires a well-defined, nonsteady flow	 Cleveland, Ohio 44135 
	
source in which to calibrate the probes. Such a non-	 Reference: B72-10403 
steady flow direction generator is described in the 
	
technical support documentation for this Tech Brief. 	 Patent status: 
2. The following documentation may be obtained from: 	 No patent action is contemplated by NASA. 
National Technical Information Facility 
Springfield, Virginia 22151 	 Source: L. N. Krause and R. L. Summers 
Single document price $3.00
	 Lewis Research Center 
(or microfiche $0.95)
	 (LEW-1 1499) 
B72-10403	 Category 06


Nonsteady flow-direction measurement

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