Henderson, Jason (2001) Investigation of cavity flow aerodynamics using computational fluid ...

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Henderson, Jason (2001) Investigation of cavity flow aerodynamics using
computational fluid dynamics. PhD thesis.

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Investigation Cavity Flow
of
Aerodynamics Using
Computational Fluid Dynamics
Jason Henderson, B. Eng
Thesis to the Faculty Engineering,
submitted of
University Glasgow, for Degree Doctor Philosophy
the
of of of
University Glasgow
of
Department Aerospace Engineering
of
August 2001
© 2001 Jason Henderson
ALL MISSING PAGES ARE BLANK
IN
ORIGINAL
BEST COPY
AVAILABLE
Variable
print quality
Dedicated father, James,
to
my my mother,
Norah, Kirsty.
and my wife,
Abstract
The bomb bay large
acoustic environment of a or cavity causes pressure oscillations
[68].
the them is that has intrigued for
and severity of a problem researchers years
Many have been degrees
techniques
suppression applied with varying of success.
Despite how
this, the the the
understanding of why pressure oscillations exist or
have been investigated thoroughly. Advances in
suppression methods work not as
CFD be
the to to
permits modelling of cavity environment performed and reveal
details the flow is difficult to from The
about which obtain experiments. contribu-
tion this thesis is to investigate the flow for flows the CFD
of physics cavity and use
theroretical information to
results synergistically with experimental and enhance
the the
understanding of problem.
The is
the
realism of computational aerodynamics method substantially validated
before investigation the flow features is is the
any of performed, which motivation of
this The the is discussed to the
work. verification of approach with regards problem
discretisation for flows. The is
of grid cavity approach validated against experimen-
tal data for transitional-open, transtional-closed, flow from
open, and closed cavity
Mach 0.6 to Mach 1.35. For flow traces taken the floor
open cavity pressure on of
from Other
the cavity agree well with those obtained experiment. characteristics of
the flow data the instils that
agree well with experimental and validation confidence
flow
the
physics simulated.
Open flow is that interest to The flow is typical to
cavity of most researchers.
that found to exist in the bomb bay of the F-111 and is characterised by intense
is included
levels. A the
acoustic review of work of previous experimental researchers
for the findings the thesis. The flow physics indicate that
comparison with of present
111
travel downstream in the driven by
a series of vortices cavity and are vorticity gener-
lip When downstream
the the the
ated at upstream of cavity. strengthened moving
influences the the trailing initiating
vortex mass addition and expulsion at edge a
by
the
pressure wave which propagates upstream and sustains process completing
the feedback lopp. These features in the thesis. The
are elucidated upon present
flow Mach 0.85 Mach 1.19 is differences in the
at and analysed with only external
being for higher Mach
the
stream apparent number case.
The the is investigated by the
suppression of acoustic environment sloping aft wall
the The the CFD to the
of cavity. results of study are used examine why sloping of
is It is that the flow tends towards
aft cavity wall successful. shown a steady state
the to the hypothesis Heller Bliss. This hypothesis
and results are compared of and
is by the in doing the demonstrates
substantiated present simulations and so work
the CFD to be tool in
ability of used as a conjunction with experimental methods
to the flows.
enhance understanding of cavity
An flows for information is is for the transitional
area of cavity which sparse cavity
flows. the literature that the 4 types flow
a review of shows of cavity exist at super-
these identified by the CFD. The the
sonic speeds and are results of computational
to the impingement
study are used examine when and exit shocks, characteristic
flow, to form This is defined
of closed cavity collapse a single shock wave. point
L/Dcrit
the the
as and occurs when vertices of seperation and recompression wakes
It the boundary between transitional-closed flow flow
merge. represents and closed
CFD Prandtl-Meyer
the to theory investigating
and predictions are compared
when
L/D,,.
the
position of
it.
Similar flows for
Previously
cavity subsonic speeds are examined. only one type
transitional flow believed to The CFD that transitional
of was exist. study shows
flow be further transitional-open transitional-closed flow
can classified as and at sub-
Mach A
in terms
sonic numbers. previous experimental study was extremely useful
of providing the pressure distributions used to classify cavity flows today. How-
ever it was not too instructive about the flow features occurring in the transitional
iv
CFD is to investigate the flows indicates
cavities. used and erroneous conclusions
derived from due lack Once
the to tappings. this
experimental results a of pressure
is identified, the the flow indicators
other characteristics of are examined as possible
flow The CFD be
to the type to
of occurring. value of used synergistically with
information is demonstrated is theme that through
experimental clearly and a runs
this thesis.
V
Acknowledgement
s
I like to to Dr. Ken Badcock
would express my sincere gratitude my supervisors and
Prof. Bryan Richards. Their
continual assistance and encouragement and relentess
have been Thanks to the
enthusiasm greatly appreciated. also other members of
the CFD Mark Woodgate, for their help the three
group, especially all over past
Special thanks is to John Ross from DERA Bedford for
years. extended generously
data fruitful discussions during the the
providing experimental and course of study
I like to to Ian Wrisdale the Defence Evaluation
would also express my gratitude at
Research Agency, Bedford for his
and advice and practical assistance.
This is by from DERA Bedford.
work supported sponsorship
vii
Contents
Abstract
111
Acknowledgements
vii
ix
Contents
List Figures
xii
of
Nomenclature
xviii
1 Introduction I
2 Simulation details 9
2.1 Overview 9
..................................
2.2 Mathematical Models 9
...........................
2.3 Turbulence Influences for Cavity Flows 10
.................
2.3.1 Algebraic based 11
studies
......................
2.3.2 Two kinetic based 12
equation energy studies
...........
2.3.3 Summary RANS Modelling 13
of
..................
2.3.4 Validity RANS 13
of
.........................
2.4 Numerical Method Data Analysis 14
and
..................
2.4.1 Numerical Method 14
........................
2.4.2 Data Analysis 15
...........................
2.5 Open Subsonic Supersonic Flow 17
and
..................
2.5.1 Description Experimental Test Cases 17
of
.............
Experimental Data 17
........................
LX