Preliminary investigation of the delay of turbulent flow separation by means of wedge-shaped bodies Page: 2 of 31
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NACA RM ABOL12 G lLE 'C
NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS
PRELIMINARY INVESTIGATION OF THE DELAY OF TURBULENT
FLOW SEPARATION BY MEANS OF WEDGE-SHAPED BODIES
By George B. McCullough, Gerald E. Nitzberg,
and John A. Kelly
An experimental investigation of pyramidal, wedge-like bodies as
devices for delaying separation of a turbulent boundary layer was under-
taken. Tests of individual wedges on a large flat plate showed that,
within certain limits, effective boundary-layer control could be obtained
with wedges of different geometry, but that the drag of the wedges was
high, making it desirable to keep the size of the wedges to a minimum.
Tests of multiple small wedges attached to a two-dimensional
NACA 633-018 airfoil model showed that greater maximum lift was attained
by placing the wedges well forward along the chord, and by allowing open
spaces between adjacent wedges. The best arrangement found increased
the maximum lift of the airfoil about 45 percent at the expense of
doubling the zero-lift drag. Similar gains were achieved by the use of
small, vane-type vortex generators at about half the cost in drag.
This report is concerned with an attempt to control the growth of a
turbulent boundary layer by means of wedge-shaped bodies similar to the
one shown in figure 1. The method was suggested by consideration of the
types of flow associated with the NACA submerged inlet (reference 1), and
the vane-type vortex generators described in reference 2.
Studies of the flow in the NACA submerged inlet indicated that,
although a pair of vortices existed in the lee of the divergent walls of
the inlet, the principal mechanism exerting a thinning action on the
boundary layer on the floor of the inlet was the lateral spreading of the
flow caused by the divergent walls. Also, the United Aircraft Corpora-
tion has shown that a turbulent boundary layer can be re-energized by
a utilizing the circulation of trailing vortices shed from the tips of
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McCullough, George B.; Nitzberg, Gerald E. & Kelly, John A. Preliminary investigation of the delay of turbulent flow separation by means of wedge-shaped bodies, report, March 1, 1951; (digital.library.unt.edu/ark:/67531/metadc58702/m1/2/: accessed February 17, 2019), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.