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Costal Inlets Research Program
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Figure 49. Comparison of horizontal flow magnitudes in lee of a vertical step
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separation at a
vertical
edge
resulting
in a
free
jet,
(b)
flow
separation at a
vertical
edge
with
a constrained
jet,
(c)
flow
separation at a
sloping
edge
resulting
in a
free
jet,
and
(d)
flow
separation at a
vertical
step.
In
all
cases
the
impact
of
model
distortion
was
evaluated
by
comparing
the
measured
velocity
fields
of the
prototype
experiment
with
the
velocity
fields
of the
distorted
models
scaled
to
prototype
size
using
appropriate
scale
ratios.
Judging
whether
or
not
good
similitude
existed
between
model
and
prototype
was
subjective,
and
good
correspondence
was
noted
where
variations
between
vector
fields
were
thought
to be
small
enough
to have
been
caused
by
measurement
error
or
small
misalignment
of
boundary
geometry
between experiments.
The
conclusions
from
the
turbulence
scale
effects experiments
are
as
follows:
a.
Flow
separation and
turbulence
generated at
vertical
edges
will
not
have
a
scale
effect
in
geometrically
distorted
models
because
vertical
turbulent
fluctuations
are
small.
b.
Flow
separation at
vertical
edges
with
constraining
downstream
jetties
will
be
similitude
in
distorted
models
with
good
correspondence
in
resulting
flow
patterns
in the
main
flow
and in the
entrainment
region.
c.
Flow
separation at a
vertical
step
where the
turbulence
is manifested
primarily
in the
vertical
plane
will
not
have
any
significant
scale
effect
in
geometrically
distorted
models.
d.
Flow
separation
initiated
by a
sloping
edge
will
exhibit
a
scale
effect
in
geometrically
distorted
models.
However,
the
scale
effect
is
strongest
near
the
bottom
and
appears
to
lessen
closer
to the
free
surface.
Also,
the
scale
effect
seemed
to be restricted to the
immediate
vicinity
of the
jet
boundary;
however,
potential
impacts
farther
downstream were
not
evaluated
due to the
limited
measurement
region
of the experiments.
e.
Evaluation
of
potential
turbulent
scale
effects in proposed
distorted
physical
models requires
good
understanding
of
dominant
flow
patterns
in the
prototype
along
with
knowledge
of
boundaries
where
flow
separation
and/or
turbulence
generation
might
occur.
Evaluation
must
be
site-specific.
f.
Importance
of
turbulent
scale
effects is a
geometrically
distorted
physical
model
relates
directly
to the
problem
being
studied,
and
whether
or
not
flow
turbulence
is a
dominant
forcing
of
that
problem.
66
Chapter
5
Turbulence
Scale
Effects
Experiments
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