Abstract
Space–time correlations and frequency spectra
of wall-pressure fluctuations, obtained
from direct numerical simulation, are examined to reveal the effects of
pressure
gradient and separation on the characteristics of wall-pressure fluctuations.
In the
attached boundary layer subjected to adverse pressure gradient, contours
of constant
two-point spatial correlation of wall-pressure fluctuations are more elongated
in the
spanwise direction. Convection velocities of wall-pressure fluctuations
as a function
of spatial and temporal separations are reduced by the adverse pressure
gradient.
In the separated turbulent boundary layer, wall-pressure fluctuations are
reduced
inside the separation bubble, and enhanced downstream of the reattachment
region
where maximum Reynolds stresses occur. Inside the separation bubble, the
frequency
spectra of wall-pressure fluctuations normalized by the local maximum Reynolds
shear
stress correlate well compared to those normalized by free-stream dynamic
pressure,
indicating that local Reynolds shear stress has more direct influence on
the wall-pressure spectra. Contour plots of two-point correlation of wall-pressure
fluctuations
are highly elongated in the spanwise direction inside the separation bubble,
implying
the presence of large two-dimensional roller-type structures. The convection
velocity
determined from the space–time correlation of wall-pressure fluctuations
is as low
as 0.33U0 (U0 is the maximum inlet
velocity) in the separated zone, and increases downstream of reattachment.
Publisher
Cambridge University Press (CUP)
Subject
Mechanical Engineering,Mechanics of Materials,Condensed Matter Physics
Cited by
124 articles.
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