Prediction of heat, mass, species, and momentum fluxes in a space vehicle and aerodynamic noise production by supersonic jet and rocket exhausts requires a predictability of the associated turbulence fields. The hot wire is a technique that will allow an experimental determination of turbulent properties

Hanson, A. R.

Krause, F. R.

Larson, R. E.

English

NASA Technical Reports Server

December 1966	 Brief 66-10687 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Study of Hot Wire Techniques in Low Density Flows with High Turbulence Levels 
Large turbulence levels in the separation and re-
attachment regions of free shear layers produce severe 
heat fluxes that emphasize the urgent need for a 
technique that will allow an experimental determina-
tion of turbulent properties. The prediction of heat, 
mass, species, and momentum fluxes in a space 
vehicle and a more detailed understanding of aero-
dynamic noise production by supersonic jet and 
rocket exhausts require a predictability of the as-
sociated turbulence fields. 
Flow phenomena and heat transfer have been 
studied behind a blunt trailing edge in a two-dimen-
sional, supersonic shear with a turbulent forebody 
boundary layer. 
To date, the hot wire is the only instrument that has 
been applied successfully to turbulence investigated 
in shear layers. The proposed measurements are, 
however, unusual since the rms levels in the recircula-
tion zones of interest might very well be so large that 
they are comparable to the mean value. 
A review of hot-wire heat loss equations indicates 
that a time invariant frequency response can be 
obtained at high turbulence levels only if the probes 
are operated at a constant temperature. The static 
calibration of two modern constant-temperature hot-
wire systems combined with hot-wire and hot-film 
sensors was used. The two systems were a modified 
Kovasznay circuit and the DISA anemometer. These 
calibrations showed significant changes at low den-
sities approaching one percent of atmosphere. Also, 
there was a large increase of wall proximity effects 
at low densities. At a pressure of approximately 0.1
atmosphere, the effect of a wall at room temperature 
is detectable at approximately 1000 hot-wire radii. 
Considerable changes were found to occur in the 
slope of the wire resistance temperature relation. This 
is especially true at low temperatures. These changes 
are attributed to impurities and results of the me-
chanical drawing process which make it necessary 
to repeat the resistance-temperature calibration for 
each consignment of wire. 
A summary of the extensive static and dynamic 
calibrations of modern hot-wire systems that might 
be used in low density flows with high relative fluctua-
tion levels is contained in a technical report, "Hot 
Wire Techniques in Low Density Flows with High 
Turbulence Levels," by A. R. Hanson and R. E. 
Larsoh of Litton Systems, Inc., and F. R. Krause 
of Marshall Space Flight Center. The report is avail-
able from:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B66-10687 
Patent status: 
Inquiries about obtaining rights for the commercial 
use of this invention may be made to NASA, Code 
GP, Washington, D.C. 20546. 
Source: A. R. Hanson, R. E. Larson
of Litton Systems
F. R. Krause
of Marshall Space Flight Center
(M-FS-1269) 
Category 01 
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 hot wire techniques in low density flows with high turbulence levels

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