22nd Congress of International Council of the Aeronautical Sciences, Harrogate, UK, 28 August - 1st September, 2000
Paper ICAS 2000-2.9.R1
ADVERSE REYNOLDS NUMBER EFFECT ON MAXIMUM LIFT OF TWO DIMENSIONAL AIRFOILS
K. Yoshida, M. Noguchi
NATIONAL AEROSPACE LABORATORY, Japan
Keywords: transition, short bubble, turbulent separation, naca 8318, wind tunnel test
An adverse Reynolds number effect on C!max of
NACA 8318 airfoil was experimentally
investigated, using a rectangular wing model
with an aspect ratio of 5.7. At a little lower
Reynolds number than that of old test data by
NACA, a slight decrease of the C!max , namely
the adverse effect was confirmed. Furthermore,
short bubble that did not play a major role in
the old explanation given by Tani was also
observed at the condition showing the adverse
effect. The adverse effect is clearly based on the
forward movement of turbulent separation
point, and we assumed new mechanism that the
forward movement was dominated by the initial
state of turbulent boundary layer at
reattachment point.
At relatively higher Reynolds numbers,
large adverse effect was also obtained and it
strongly originated in three-dimensionality of
separated flow. This means such threedimensionality
is more important in the study on
C!max of two-dimensional airfoils in addition to
the new mechanism, because turbulent
separation has almost three-dimensionality at
high Reynolds numbers.
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