Investigation of a variable Mach number supersonic tunnel with nonintersecting characteristics Page: 2 of 29
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TECH LIBRARY KAFB, NM
NACA RM No. E8J13
JE M W I!'llI llIlIIIiItllllllIllll gIIII 014359
" ' 0143594
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
INVESTIGATION OF A VARIABLE MACH NUMBER SUPERSONIC TUNNEL
WIT NONINTERSECTING CHARACTERISTICS
By John C. Evvard and DeMarquis D. Wyatt
A method is presented for the design of supersonic-wind-tunnel
nozzles that produce uniform flow over a continuously variable Mch
number range without the use of flexible walls. Experimental
results obtained from a preliminary investigation of such a tunnel
Overexpansion of the flow in the neighborhood of the throat
was observed at all Mach numbers. Boundary-layer effects were
noticeable above the design Mch number of 2.0. Mach numbers were
obtained in the range of 1.75 to 2.65 with the limits imposed by
either tunnel choking or the structural design of the tunnel. At
* any given flow-turning angler less than 1-percent variation in
ach number was observed in the test-section flow downstream of the
The usual method for obtaining a range of Mach numbers in
supersonic wind tunnels is to employ interchangeable fixed nozzle
blocks. This technique is subject to the limitations of requiring
a large number of nozzles to cover the flow range and to the dif-
ficulties of fabricating and maintaining alinement when changes in
nozzle blocks are made. Flexible-wall tunnels and sliding non-
elastic nozzle contours (reference I) have been employed to over-
come these objections. Solutions to the problem of obtaining theo-
retically perfect flow in a variable Itch number tunnel have by no
means been exhausted and study on the subject is being continued.
The difficulty in designing conventional superson T 9
for variable Match number operation without the use of flexible Walls
largely arises from problems associated with cancellation af inter-
secting characteristics originating from the flo-ezansion regions.
(For the theory of supersonic-wind-tunnel nozzi7esignplee a efer-
ence 2.) The calculation of nozzle-v ll contou. may ye simpli*led
if all the expansion wves originate on one wall re
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Evvard, John C. & Wyatt, DeMarquis D. Investigation of a variable Mach number supersonic tunnel with nonintersecting characteristics, report, November 15, 1948; (https://digital.library.unt.edu/ark:/67531/metadc64572/m1/2/: accessed March 18, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.