OENG1116
Modelling
and
Simulation
OENG1118
Sustainable
Engineering
Practice
&
Design
Project
M:
Mixing
Analysis
of
Primary
Wastewater
Digester
Note:
This
is
a
shared
Project
between
OENG1116
and
OENG1118.
Many
of
the
assessments
will
be
shared
between
OENG1116
and
OENG1118
in
that
for
a
given
assessment
you
will
need
to
prepare
one
piece
of
work
(e.g.
Group
Proposal
Report,
Group
Project
Report)
that
covers
the
requirements
of
both
OENG1116
and
OENG1118.
Marking
of
these
assessments
shall
be
performed
separately
for
each
course,
but
your
group’s
overall
recommendations
take
into
account
findings
from
both
the
Modelling
and
Simulation
and
Sustainability
Assessment
aspects
of
the
project.
BLUE
text
below
indicates
tasks
that
shall
be
assessed
by
OENG1116
only,
RED
text
below
indicates
tasks
that
shall
be
assessed
by
OENG1118
only,
and
BLACK
text
indicates
tasks
that
shall
be
assessed
by
both
courses.
1.0
Project
Task/Outline
With
increasing
population
density
and
demands
on
water
resources
in
general,
water
and
wastewater
treatment
play
an
increasingly
pivotal
role
in
modern
society.
At
the
Western
Treatment
Plant,
the
primary
digester
acts
to
digest
suspended
solids
and
biomass
into
inert
materials
and
methane
for
on-‐site
power
generation
that
may
be
used
by
the
plant
or
sold
back
to
the
grid.
It
has
been
recognized
that
the
efficiency
of
the
complex
chain
of
biochemical
digestion
reactions
within
the
digester
are
heavily
impacted
by
the
mixing
conditions
within
the
digester.
It
is
suspected
that
the
current
mixing
conditions
in
the
primary
digester
at
the
Western
Treatment
Plant
are
suboptimal,
and
may
be
attributed
to
the
highly
viscous
nature
of
the
activated
sludge
that
arises
from
the
high
biomass
content.
As
such,
whilst
it
has
been
recognized
that
the
primary
digester
could
benefit
from
improved
mixing
conditions,
conventional
approaches
to
accelerate
fluid
mixing
such
as
gas
spargers
or
mixing
impellers
are
not
appropriate
for
this
application.
Your
Engineering
Team
has
been
charged
with
the
task
of
assessing
the
current
mixing
conditions
within
the
primary
digester
and
develop
and
assess
alternate
mixing
approaches
under
laminar
flow
conditions
such
as
the
use
of
internal
baffles
and/or
steady
or
transient
fluid
extraction
and
reinjection,
the
outcomes
of
which
will
be
communicated
to
the
client
via
a
professional
engineering
report
which
outlines
the
project
recommendations
and
feasibility.
Your
Engineering
Team
based
within
a
professional
engineering
firm
is
interested
in
undertaking
this
assessment
project
that
is
comprised
of
the
following
tasks:
• Develop
a
computational
fluid
dynamics
(CFD)
model
of
the
flow
conditions
within
the
primary
digester
under
the
different
mixing
approaches
and
develop
a
measure
of
the
mixing
efficiency
across
these
cases
• Estimate
the
energy
consumption
of
the
alternate
approaches
and
develop
recommendations
based
upon
the
offset
between
mixing
and
energy
efficiency.
• Conduct
a
preliminary
sustainability
assessment
to
quantify
and
qualify
impacts
of
the
solution
on
the
economy,
environment,
and
society
• Conduct
a
multi-‐criteria
analysis
to
decide
on
an
optimal
variant
of
the
solution
• Make
and
justify
recommendations
as
to
whether
the
project
should
proceed
based
on
the
outcomes
of
the
tasks
above
This
information
will
allow
the
benefits
of
the
project
to
be
estimated
and
the
overall
feasibility
of
the
project
to
be
gauged.
As
detailed
in
the
assessment
descriptions
for
OENG1116
and
OENG1118,
your
Engineering
Team
will
first
develop
a
proposal
that
will
act
as
a
competitive
bid
for
this
assessment
project.
Assuming
that
this
bid
is
successful,
your
Engineering
Team
will
then
undertake
the
assessment
project
itself.
The
assessment
project
tasks
are
outlined
in
detail
as
follows:
2.0
Typical
design
questions
–Mixing
Analysis
1. Find
or
estimate
details
of
the
primary
digester
at
the
Western
Treatment
Plant,
including
a. Digester
dimensions
and
geometry
b. Input
flow
rate
c. Digester
fluid
rheology
2. Using
a
suitable
software
package
develop
a
two-‐dimensional
(2D)
preliminary
CFD
model
of
the
existing
primary
digester
at
the
Western
Treatment
Plant
a. Verify
model
through
convergence
testing
of
mesh
and
time-‐stepping
b. Solve
steady-‐state
flow
in
digester
c. Develop
measure
of
mixing
efficiency
of
digester
and
solve
steady-‐state
mixing
efficiency
3. From
2D
model
above,
identify
regions
of
poor
mixing
in
the
primary
digester
and
suggest
potential
interventions
to
improve
mixing
efficiency,
such
as
a. Internal
baffles
and
mixing
elements
b. Judicious
extraction
and
re-‐injection
of
fluid
4.
Model
digester
flow
and
mixing
over
several
different
mixing
protocols
and
measure
a. Mixing
efficiency
and
robustness
b. Energy
consumption
5. Develop
recommendations
for
improvement
of
the
mixing
efficiency
in
the
primary
digester
and
feasibility.
Comment
on
shortcomings
of
model
and
scope
for
improvement.
3.0
Typical
design
questions
–
Sustainability
Assessment
Environment
For
all
products
in
the
scenarios:
1. Formulate
a
single
functional
unit.
2. Determine
a
single
system
boundary.
For
the
products
in
each
scenario:
3. Identify
the
major
material-‐
and
energy-‐conversion
processes
across
the
product
life
cycle.
4. Determine
the
major
material
and
energy
flows.
5. Draw
a
process
flow
diagram
that
includes:
5.1. processes
5.2. elementary
flows
of
materials
and
energy
5.3. intermediate
flows
of
materials
and
energy
6. Calculate
the
largest
environmental
impacts.
7. Calculate
the
sensitivity
of
parameters
with
high
contributions
and
high
uncertainty,
and
of
assumptions.
Economy
For
the
solution
in
each
scenario:
1. Identify
sources
of
cost
and
revenue
across
the
product
life
cycle.
2. Determine
the
economic
costs
and
revenues.
3. Determine
the
useful
life
of
the
product.
4. Calculate
the
payback
period
and
net
present
value
of
the
product.
Society
For
the
solution
in
each
scenario:
1. Identify
the
societal
impacts
from
the
project
(both
positive
and
negative
impacts).
Multi-‐criteria
decision
analysis
1. Identify
a
variety
of
criteria
or
objectives
with
justifications
for
multi-‐criteria
analysis.
2. Determine
the
appropriate
weightings
for
each
criterion/objective
with
justifications.
3. Determine
the
measure
of
the
effectiveness
of
the
project/alternative.
4.0
Useful
resources
Software
tools
1. Fluid
dynamics
software:
• ANSYS-‐CFX
2.
Modelling
equations
and
theoretical
underpinnings
Discuss
the
governing
equations
that
will
be
solved
and
their
theoretical
underpinnings.
Identify
and
discuss
assumptions
involved
and
their
validity.
3.
Numerical
techniques
and
software
packages
Discuss
the
numerical
techniques
you
will
employ
to
solve
the
governing
equations
and
the
software
package
used.
Discuss
issues
regarding
accuracy
and
stability
of
numerical
solutions.
Identify
possible
ways
to
cross-‐validate
numerical
predictions