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Eulerian-Lagrangian analysis of transport and residence times in estuaries and coasts
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Eulerian-Lagrangian analysis of transport and residence times in estuaries and coasts
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87557211142007_199710.oliveira.anabela.pdf
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http://www.ohsu.edu/xd/education/library/services/theses-dissertations/rights-statement.cfm
Title
Eulerian-Lagrangian
analysis
of
transport
and
residence
times
in
estuaries
and
coasts
Creator.PersonalName
Oliveira
,
Anabela
Pacheco
de
Thesis.Degree
Ph.D.
Thesis.Major
Environmental Science and Engineering
Thesis.DateDegreeAwarded
October
1997
Institution
Oregon Graduate Institute of Science & Technology
Department
Dept. of Environmental Science and Engineering
Thesis.Advisor/Mentor
Baptista, António Manuel
Thesis.Committee
Fish, William
Jay, David A.
Russell, Thomas F.
Subject.LCSH
Numerical calculations -- Computer programs
Coasts -- Models
Lagrange equations
Call Number
Q183.5.OGI O455a 1997
Description.Abstract
Eulerian-Lagrangian
methods
(ELMs)
are
increasingly
used
to
simulate
groundwater
and
surface
water
transport
and
water
quality
,
largely
due
to their
ability
to
use
large
time
steps
and to
formally
decouple
processes
with
distinct
time
scales
.
Yet
,
two
severe
limitations
remain
:
(1)
ELMs
do
not
inherently
conserve
mass
, and
(2)
in
multiple
dimensions
,
robust
implementations
of "
higher-order
"
ELMs
are
expensive
.
Our
research
focused
on the
understanding
of the
main
sources
of
errors
in
ELMs
.
We
analyzed
systematically
the
impact
and
relative
importance
of
tracking
errors
,
integration
errors
and
forcing
by
non-conservative
flow
fields
, on
measures
of
mass
conservation
,
overall
accuracy
and
stability
. From this
analysis
,
we
propose
new
methodologies
and
general
guidelines
towards
mass
conservative
,
globally
accurate
and
stable
multidimensional
ELM
transport
simulations
in
estuarine
and
coastal
regions
.
We
performed
a
pioneering
study
of the
influence
of
tracking
errors
,
demonstrating
their
very
strong
negative
impact
on
mass
conservation
,
overall
accuracy
and
stability
.
Low-order
tracking
methods
are
strongly
discouraged
in the
presence
of
complex
flow
fields
,
typical
of
estuaries
,
because
they are
too
inaccurate
to
allow
overall
mass
balance
and
phase
preservation
, and they
lead
to
potential
instability
.
We
show
that the
evaluation
of the
integrals
at the
feet
of the
characteristic
lines
is
an
important
source
of
mass
and
overall
errors
,
which
can
be
controlled
through
grid
refinement
. To
avoid
such
errors
,
we
develop
a
new
method
that
combines
the
flexibility
and
local
mass
properties
of
control
volume
finite
element
methods
(CVFE)
, with a
new
quadrature
integration
technique
.
Subdivision
quadrature
overcomes
stability
constrains
of
traditional
quadratures
and
allows
for
easy
implementation
in
multiple
dimensions
.
We
find
subdivision
quadrature
CVFE-ELMS
to be an
attractive
alternative
to
current
finite
element
ELMs
in
estuaries
and
coasts
.
Non-conservative
flow
fields
are the
primary
concern
for
estuarine
and
coastal
applications
because
ELMs
cannot
mitigate
their
effect
without
jeopardizing
overall
accuracy
.
We
found
bathymetric
gradients
and
complex
geometry
to be the
main
sources
for
flow
mass
errors
, and
grid
refinement
to be
inadequate
to
eliminate
them.
Consequently
,
mass
imbalances
in
ELM
solutions
cannot
be
removed
by
grid
refinement
.
Control
volume
finite
elements
and
conservative-equation-based
formulations
are
equally
ineffective
in the
presence
of a
non-conservative
flow
. The
problem
needs
to be
addressed
at the
source
,
i.e.
, the
circulation
models
that
generate
the
flows
. A
detailed
analysis
of
residence
times
illustrates
the
importance
of
improving
numerical
models
, and
provides
new
insights
on the
variability
of
residence
times
in
estuarine
systems
. A
new
methodology
is
proposed
,
which
emphasizes
the
importance
of
local
analysis
of
residence
times
to
understand
the
fluxing
properties
of a
complex
system
,
while
providing
an
alternative
approach
to
traditional
bulk
evaluations
of
residence
times
.
Language
eng
Type
Text
Format.Use
Needs Adobe Acrobat Reader to view.
Format.FileType
pdf
Format.FileSize
9193.648 KB
OCLC number
41073853
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