Transition Caused by the Laminar Flow Separation Page: 2 of 15
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TECH LIBRARY KAFB, NM
0144487
G NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
TECHNICAL MEMORANDUM 1352
TRANSITION CAUSED BY THE LAMINAR FLOW SEPARATION*
By T. Maekawa and S. Atsumi
INTRODUCTION
A great number of discussions have long been made to explain the
cause of transition from laminar to turbulent flow in the bouridary layer;
none of them has as yet led to a definite conclusion. Many attempts have
been put forward to calculate the transition theoretically by considering
the stability of the boundary layer with superimposed infinitesimal dis-
turbances. But the results do not agree with experiments except in the
case of the transition in the flow between concentric rotating cylinders
discussed by Taylor (ref. 1). (According to Nature, December 14, 1946,
it is reported that Dryden has succeeded in showing the agreement between
the calculated result by stability theory and the transition observed in
a wind tunnel of low stream turbulence, but we know nothing about the
details.)
Another example of the breakdown of laminar flow is the case when
the boundary layer flow separates from the surface while it is laminar.
There are two cases; in one case the separated flow leaves the surface
forever, while in'the other case the separated flow becomes turbulent
due to its instability and reattaches to the surface as a turbulent
boundary layer. The latter case is a kind of transition, and there are
many experimental examples in which such a sort of transition appears.
The transition which occurs when there is a steep rise in surface pres-
sure distribution seems to be mostly due to this mechanism. The sudden
change in drag or maximum lift occurring in a certain range of Reynolds
numbers is considered to depend upon whether or not the separated flow
reattaches to the surface. In spite of such an importance in practice,
very few studies have been made concerning this problem, except for
Von Doenhoff's kinematical speculation deduced from a simple experiment
(ref. 2), Tani's postulate of constant Reynolds number at the laminar
separation point based on dimensional analysis (ref. 3), and Inoue's
discussion of Von Doenhoff's speculation (ref. 4). Experiments were
therefore made to examine the effects of the geometry of body surface,
Reynolds number, stream turbulence and a roughness element (wire) on the
reattachment of separated flow, with a view to inquiring about the
mechanism of transition caused by separation and hence to understanding
the effect of Reynolds number on the flow characteristics.
"Sjryu-Buri ni tomonau Sen'i ni kansuru Kenkyu." Journal of
the Society of Applied Mechanics, Japan, vol. i, no. 6, Nov. 1948,
pp. 187-192.
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Maekawa, T. & Atsumi, Shoichi. Transition Caused by the Laminar Flow Separation, report, September 1952; (https://digital.library.unt.edu/ark:/67531/metadc62935/m1/2/: accessed April 19, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.