Frequency selection mechanisms in the flow of a laminar boundary layer over a shallow cavity
File(s)
Accepted version
Author(s)
Qadri, UA
Schmid, PJ
Type
Journal Article
Abstract
We investigate the flow over shallow cavities as a representa
tive configuration for modelling small
surface irregularities in wall-bounded shear flows. Due to t
he globally stable nature of the flow, we
perform a frequency response analysis, which shows a signifi
cant potential for the amplification of
disturbance kinetic energy by harmonic forcing within a cer
tain frequency band. Shorter and more
shallow cavities exhibit less amplified responses, while en
ergy from the base flow can be extracted
predominantly from forcing that impacts the cavity head-on
. A structural sensitivity analysis,
combined with a componentwise decomposition of the sensiti
vity tensor, reveals the regions of
the flow that act most effectively as amplifiers. We find that the fl
ow inside the cavity plays a
negligible role, whereas boundary layer modifications imme
diately upstream and downstream of
the cavity edges contribute significantly to the frequency r
esponse. The same regions constitute
preferred locations for implementing active or passive con
trol strategies to manipulate the frequency
response of the flow.
tive configuration for modelling small
surface irregularities in wall-bounded shear flows. Due to t
he globally stable nature of the flow, we
perform a frequency response analysis, which shows a signifi
cant potential for the amplification of
disturbance kinetic energy by harmonic forcing within a cer
tain frequency band. Shorter and more
shallow cavities exhibit less amplified responses, while en
ergy from the base flow can be extracted
predominantly from forcing that impacts the cavity head-on
. A structural sensitivity analysis,
combined with a componentwise decomposition of the sensiti
vity tensor, reveals the regions of
the flow that act most effectively as amplifiers. We find that the fl
ow inside the cavity plays a
negligible role, whereas boundary layer modifications imme
diately upstream and downstream of
the cavity edges contribute significantly to the frequency r
esponse. The same regions constitute
preferred locations for implementing active or passive con
trol strategies to manipulate the frequency
response of the flow.
Date Issued
2017-01-10
Date Acceptance
2016-12-13
Citation
Physical Review Fluids, 2017, 2
ISSN
2469-990X
Publisher
American Physical Society
Journal / Book Title
Physical Review Fluids
Volume
2
Copyright Statement
© 2017 American Physical Society.
Subjects
Science & Technology
Physical Sciences
Physics, Fluids & Plasmas
Physics
BACKWARD-FACING STEP
3-DIMENSIONAL INSTABILITIES
STABILITY ANALYSIS
NOISE AMPLIFIERS
SENSITIVITY
Publication Status
Published
Article Number
013902