Author:
SAATHOFF P. J.,MELBOURNE W. H.
Abstract
Wind-tunnel experiments were conducted to investigate the cause
of large
pressure
fluctuations near leading edges of sharp-edged bluff bodies. Measurements
obtained
with a blunt flat plate showed that very low pressures occur in a narrow
region
located
approximately 0.25XR from the leading edge,
where
XR defines the distance from the
leading edge to the mean reattachment location. This phenomenon occurs
in the
undisturbed flow as well as turbulent flow, although the magnitude of peak
pressure
fluctuations increases with both turbulence intensity,
σu/u,
and turbulence scale, LX.Flow visualization experiments conducted with a high-speed cine-camera
reveal the
process that causes large pressure fluctuations in separation bubbles.
This
process is
initiated when a perturbation in the approaching flow causes a roll-up
of
the separated
shear layer, producing a strong vortex near the surface. Conditional sampling
of
pressure data was used to determine the spanwise length of the vortex.
A significant
increase in the spanwise correlation of pressure fluctuations occurs when
the shear
layer rolls up. Coherence measurements indicate that the spanwise length
of vortices
in the separation bubble is not directly related to longitudinal velocity
fluctuations in the free-stream.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
110 articles.
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