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National Advisory Committee for Aeronautics, Technical Notes - Turbulent Shearing Stress in the Boundary Layer of Yawed Flat Plates

Hot—wire anemometer measurements of the turbulent shearing stress
in a turbulent boundary layer on a yawed flat plate are presented. Two
plates with angles of yaw of 0° and #50 were studied. Measurements of
the intensity of turbulence were made simultaneously with the shear
measurements, using a technique developed by the author. The experi-
mental procedure is reviewed briefly and an attempt is made to evaluate
the precision of the results.

The measured velocity profiles are used to calculate the shear
distribution and the result is compared with the result of experimental
shear measurements.

The unyawed—flat—plate data agree well with calculated results,
whereas the H50 data are apparently not amenable to calculation. Some
speculative remarks are included in an attempt to explain the discrepancy.

The problem of the turbulent boundary layer has engaged the attention
of aerodynamicists for many years. The mathematical difficulties entailed
in a theoretical analysis of the problem have inevitably led to a strong
dependence on experimental studies. In order to obtain any insight into
the turbulent boundary layer, it is necessary to consider as simple an
experimental setup as possible. That is, problems of the mechanism of
transition and of the behavior of a two-dimensional turbulent boundary
layer without pressure gradient and similar fundamental problems have
had to be attacked; though some.of these problems have not been solved,
at least some light has been thrown on the subject so that more complex
phenomena can be studied. It is not too surprising, therefore, to find
little in the literature regarding three-dimensional turbulent boundary
layers, when the two—dimensional turbulent—boundary—layer problem can
scarcely be considered near solution.

During the past decade, however, some interest has been shown in
the problem of the turbulent boundary layer on a yawed cylinder, which ¢
is probably the simplest three—dimensional case that might be considered.
The impetus to this interest in the yawed turbulent boundary layer was
given primarily by the work of Prandtl (ref. 1), Jones (ref. 2), and
Sears (ref. 5) who showed that for the laminar boundary layer on a
yawed cylinder, the boundary—layer equations in the chordwise direction
are independent of the flow along the span; that is, the flow past a
yawed cylinder may be expressed in terms of the flow at right angles to
the same cylinder.