<DOC>
<DOCNO>
798
</DOCNO>
<TITLE>
interaction between shock waves and boundary layers, with a note on the
effects of the interaction of the performance of supersonic intakes .
</TITLE>
<AUTHOR>
holder, d.w., pearcey, h.h. and gadd, g.e.
</AUTHOR>
<BIBLIO>
a.r.c., c.p. 180, february 1954 .
</BIBLIO>
<TEXT>
the interaction between shock waves and boundary layers has important
effects in many problems of high-speed flow . this paper has been written
as a guide to the literature on the subject, and as a critical
review of the present state of knowledge concerning both the underlying
physical processes and the practical applications . it will be clear to
the reader that, although substantial progress has been made, our knowledge
is still far from complete and that more work both of a fundamental
nature and on specific applications is needed before the problem
is understood sufficiently well for design purposes .
part i of the paper describes experiments on comparatively simple types
of flow designed to provide fundamental information and to assist in the
 development of the theory . these experiments show that the interaction
 depends mainly on the mach and reynolds numbers and on the strength of
the shock wave . in particular, the interaction of a shock wave with a
laminar boundary layer is shown to produce much larger effects than if
the boundary layer is turbulent . for most cases where the effects of
the interaction are large enough to have serious practical consequences
it is found that the boundary layer separates from the surface, and the
difference between the interaction with laminar and turbulent layers
arises mainly because the laminar layer separates much more readily in
an adverse pressure gradient . the details of the interaction downstream
 of the separation point thus depend critically on the behaviour of the
separated layer, and on the conditions under which it reattaches to the
surface .
many of the features found in the fundamental experiments appear also in
 practical applications and these are considered in parts ii and iii of
the paper . although the emphasis hero is on the performance of aerfoils
and wings moving at high subsonic speeds, the importance of the
interaction in other examples such as at supersonic trailing edges and
in supersonic intakes is also discussed briefly . the differences between
the interaction with laminar and turbulent boundary layers are
often a source of serious discrepancy between model experiments and
full-scale conditions . for small-scale models it is, therefore, frequently
essential to make the boundary layer turbulent by artificial
means . some of the difficulties involved in doing this, and certain of
the more promising methods are briefly discussed . it is shown that
experiments on models with transition fixed can be used to explain a
number of aerodynamic effects encountered in transonic flight, and
connected with the occurrence of shock-induced separation of the turbulent
boundary layers . for both two-dimensional aerofoils and straight
 and sweptback wings, turbulent separation occurs for shocks above a
certain strength which applies for both model and full-scale conditions
full-scale conditions,. differences in magnitude would be expected if
the pressure recovery along the separated layer between the shock and
the trailing edge is affected by reynolds number, but little information
 is at present available on this point .
most of the repercussions of turbulent separation on the steady-motion
characteristics of aerofoils and wings can be traced to the associated
reduction in the pressure recovery over the roar of the surface . this
is because the pressure at the trailing edge controls the inter-relation
 between the two surfaces /so long as the flow at the trailing edge
remains subsonic/, and in particular the relative movements of the shock
 waves and the extents of the local regions of supersonic flow . certain
 unsteady-flow characteristics such as buffeting and control surface
separation .
some evidence is presented on the influence of section shape on the
occurrence and effects of separation, but in this, as in many other
respects, information relevant to turbulent boundary layers is scarce .
some notes on the further work which is required are given in part iv of
 the paper .
</TEXT>
</DOC>
