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Publications in Scientific Journals:

S. Braun, A. Kluwick:
"The effect of three-dimensional obstacles on marginally separated laminar boundary layer flows";
Journal of Fluid Mechanics, 460 (2002), 57 - 82.



English abstract:
We consider the steady viscous/inviscid interaction of a two-dimensional, nearly
separated, boundary layer with an isolated three-dimensional surface mounted
obstacle. For example in the large Reynolds number flow around the leading
edge of a slender airfoil at a small angle of attack.
An integro-differential equation describing the effect of the obstacle on the
wall shear stress valid within the interaction regime is derived
and solved numerically by means of a spectral method, which is outlined in
detail. Typical solutions of this equation are presented for different values
of the spanwise width B of the obstacle including
the limiting cases B -> 0 and B -> infinity. Special emphasis is placed on the
occurrence of non-uniqueness. On the main (upper) solution branch the
disturbances to the flow field caused by the obstacle decay in the lateral
direction. Conversely a periodic flow pattern, having no decay in the spanwise
direction, was found to form on the lower solution branch. These
branches are connected by a bifurcation point, which characterizes the
maximum (critical) angle of attack for which a solution of the strictly plane
interaction problem exists. An asymptotic investigation of the interaction
equation, in the absence of any obstacle, for small deviations of this
critical angle clearly reflects the observed behaviour of the numerical
results corresponding to the different branches. As a result we can conclude
that the primarily local interaction process breaks down in a non-local
manner even in the limit of vanishing (three-dimensional local) disturbances
of the flow field.


"Official" electronic version of the publication (accessed through its Digital Object Identifier - DOI)
http://dx.doi.org/10.1017/S0022112002008066

Electronic version of the publication:
http://journals.cambridge.org/action/displayIssue?jid=FLM&volumeId=460&issueId=-1


Created from the Publication Database of the Vienna University of Technology.