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MMME4060 Computational Fluid Dynamics Coursework 2023
1. Coursework Briefing Computational Fluid Dynamics 2023
This coursework is worth 50% of this module assessment and on average
should take 50 hours.
This coursework meets learning outcomes 2, 3 and 4 for the module and
after completing this coursework you will have developed and demonstrated
Understanding of how computational fluid mechanics techniques are applied
to real fluid engineering problems,
Understanding of how computer software is used in this area and an
awareness of the limitations of computational techniques.
To lay the foundation for future research studies in fluid mechanics.
2. Background
Although a relatively simple geometry the turbulent flow physics between
the cavity and the mainstream flow can be extremely turbulent and
complex and a challenge for CFD. A consultancy wish to assess the ability
of CFD to capture the complex flow dynamics. They are particularly
concerned about certain modes of cavity flow including ‘wake mode’
where under certain conditions flow over cavities can oscillate violently
leading to structural damage and can be particularly problematic.
U
Figure 1 Simplified cavity geometry Grace et al. (2004) [2]
They wish to assess the capability of CFD to accurately simulate a
simplified cavity case as shown in Figure 1. In particular, the consultancy
are interested in an assessment of the performance of different turbulence
models and spatial discretization schemes in Ansys Fluent ranging from
the basic to advanced. How do less computationally expensive turbulence
models (e.g. 1-eqn Spalart-Allmaras) compare with more advanced
turbulence models (e.g. Reynolds Stress model) The key outcome for
them is to have a recommended approach and best practices for
modelling of cavity flows based on your simulation analysis.
The consultancy have asked you to base your assessment on the
experimental measurements of a cavity flow performed by Grace et al.
(2004) [1]. The link to a paper on the study is below and the paper is
also provided on the module Moodle page.
https://link.springer.com/article/10.1007/s00348-003-0761-3
The consultancy are requesting a 2D analysis (i.e. use a 2D mesh). In
Grace et al.’s experiments mean velocity and turbulent flow fields were
measured upstream, within and downstream of a cavity. Experiments
were performed with both laminar and turbulent upstream boundary
layers and measurements of these profiles are provided to aid
specification of simulation inlet boundary conditions. They want you to
use a laminar incoming boundary layer, the profile of which is provided in
the paper. Note that the experiments within the paper are performed
using air.
3. Ansys Fluent Resources
Ansys training will be provided at the start of the course. A wide variety
of Ansys Fluent resources are available through the module Moodle page
including user manuals, theory manuals and a tutorial manual with
appropriate files. Further help with the use of Fluent will be available in
the labs with demonstrators on-hand to provide assistance.
4. Report Format
The report will take the form of a PowerPoint presentation to be submitted
electronically (there will be no presentation; but imagine that you had 40
minutes to pitch your results to senior engineers). The report needs to
demonstrate a solid approach to deploying CFD and using it for analysis
purposes. The report must therefore first clearly describe:
– what is the background to the calculation;
– what are its specific aims;
– what is/are the case(s) (geometry, dimensions, [flow] conditions, cases
and data available and what they permit to examine);
– what is the fidelity of the data available before explaining and justifying
fully how the model is built;
The latter should cover discretisation (mesh and its suitability), boundary
conditions (how good are they, how faithful are they to the experimental
case How controlled and well defined What uncertainty might they
introduce, if suitable…), convergence criteria (general and specific, e.g. in
light of what is being investigated) and modelling approach (which models
and why are they chosen How do you show they are suited to the problem
Compatibility issues, e.g. between mesh and turbulence model ). The
results should be presented, describe them fully before evaluating them
against experimental measurements — this last step is called “validation”.
Validation should be quantitative as well as qualitative; it judges the
performance of your model against theory or the “real world” (how well do
my models describe reality ). It is not sufficient to state that results and
data “look” the same; it is not sufficient either to put two pictures next to
one another and let the reader form an opinion. You should provide
quantitative insight as much as possible. Finally, a discussion : Why the
differences How do different modelling approaches (e.g. turbulence models
& discretisation schemes affect results What recommendations would you
make What is the impact/consequence of your work/experience
Please note that the presentation should be 30 slides max – only the first
30 slides will be marked. There is no formal presentation; but imagine that
you had 40 minutes to present to senior engineers. The presentation
should contain detailed notes within Powerpoint to aid the
description of slides. These can be in bullet point format if desired.
5. Presentation Sections
Introduction (10%) – should clearly describe the task and aims and
introduce the presentation effectively. It should also provide relevant and
interesting background information
Description (10%) – should clearly describe the experimental case
(geometry, flow conditions and available data). It should highlight key
parameters, e.g. Reynolds number (based on what ), values of geometrical
parameters, flow inlet conditions. Use figures where possible to aid
description
Methodology (15%) – should provide a clear description of the CFD model
setup. Key parameters and settings should be highlighted and linked with
the experiments. This should cover the mesh, boundary conditions,
turbulence models, numerical schemes and appropriate investigations.
Results (20%) – should provide clear presentation of results, use of
appropriate range of graphs (contour, vector, streamlines). Sensitivities
should be discussed. There should be sufficient data accumulated and
presented to demonstrate the points described. Comparison should be
made with experimental measurements. Key flow physics should be
presented.
Discussion & Analysis (30%) – How do your results compare with the
experiments There should be a discusion of both quantitative and
qualitative comparisons. Can you recommend an approach How does the
flow physics look Is it realistic and as expected Can you suggest reasons
for discrepancies Sources of error
Conclusions (10%) – Draw out points from discussion and analysis.
Identify key and useful points. Give recommendations for future work.
Presentation (5%) – Good quality presentation (including layout and
figures) and effective use of notes.
6.Submission
The submission for the PowerPoint file will be via turnitin which will run
an originality report which will be visible. It is possible to run the report
through this originality checker prior to submission on Moodle (test your
text on the top banner of Moodle). The submission date for the
coursework is Friday 31st March 2023 at 17:00
To provide evidence of your use of Ansys you must submit an Excel
analysis file containing results data and plots that are used in your final
report. This will be reviewed with your report for marking but will not be
commented on/returned as part of your feedback. There will be a
separate submission box for your Excel file.
The coursework will be marked electronically and marks will be available
on Moodle. An email will be sent when it is available, normally
coursework will be returned 21 days after the submission date. Return of
coursework will be via Moodle to allow pick up during the vacation
period.
7. Marking Rubric
8.References
[1] Grace, S. M., Dewar, G. W., 2004, Wroblewski, D. E., “Experimental investigation of the
flow characteristics within a shallow wall cavity for both laminar and turbulent upstream
boundary layers”, Experiments in Fluids, Vol. 36, pp. 791 – 804.