Invitation to Tender – How to Analyse and Process CFD output
NAFEMS' Computational Fluid Dynamics Working Group (CFDWG), wishes to commission a new
document with the suggested title as outlined below:
How to Analyse and Process CFD output
Purpose
The document will form part of the “How to …?” series of books. The book will focus on the analysis and
processing of CFD output. Its aim is to equip analysts with the understanding and techniques necessary to
obtain key project data from CFD output. Part of this is to understand that the post processing starts very
early in the project and that the post processing requirements may influence the grouping of surfaces or
location of interior surfaces and model setup. The book should go further than merely illustrating how to postprocess and visualise CFD results: it should also show how to check the output of CFD software to ensure
that the results are credible and correctly reflect the intended model set-up.
The book should show an analyst how to check the output of CFD software to ensure that the results are
credible. This will include checks for physical realism; global conservation of conserved quantities; etc. The
role of visualisation and the numerical processing of CFD output should be highlighted in such checks. The
benefits and limitations of cross-checks on the credibility and consistency of CFD results through simple
calculations and comparisons to empirical data should also be covered. Whilst the main focus of the book is
on the analysis and processing of CFD output, brief coverage should also be given to checks that the flow
solver has converged, that sufficient time-steps have been simulated in an unsteady flow and that the CFD
output correctly reflects the intended model set-up, through checks on self-consistency, scrutiny of boundary
conditions, etc
The content should focus on the output of RANS models of turbulent flow. Both steady and unsteady flows
should be addressed. The book should also mention the differing requirements imposed by LES and DES,
but at an introductory level.
The book should initially describe and illustrate the need for analysis and processing of CFD output, including
the benefits of verifying the CFD model set-up and checking the credibility of results.
The main part of the book should begin by setting out the flow variables which are typically modelled in CFD,
with a description of their usefulness as regards project data. It is expected that quantities derived from the
flow variables will also be addressed, such as: mass, momentum and heat flux; shear stress; stream-function;
forces, moments and impact loads on surfaces; non-dimensional parameters; etc.
The different uses,
advantages and disadvantages of averaged values, single point values and ‘pretty pictures’ should be
explained. Issues with geometrically and physically complex 3D simulations, where there is a danger of
missing important results if arbitrary post-processing locations are used, should be commented on with tips
on how best to achieve the required output.
The book should show how post-processing and flow visualisation can play a key role in obtaining flow
variables and derived quantities from CFD output, and in a form that is useful for project requirements. The
importance of visualisation as a means to understand the output of CFD software should be stressed. The
commonly-used means of interpreting CFD output via visualisation – contour plots, iso-surfaces, vector plots,
etc. should be covered, including their benefits and disadvantages. The benefits of animation, and how these
are best realised, should also be covered.
In addition, the value of the numerical analysis of CFD output should be addressed. This includes the need
for some types of numerical analysis to be built into the simulation before it is undertaken – for example, the
calculation of quantities integrated over time in an unsteady simulation.
Comparison of results from different simulations and with test data, is an important aspect of post-processing.
Although this document should not aim to cover validation issues, which are covered in another NAFEMS
publication currently being written, guidance would be appropriate on how to compare results produced using
different modelling methods (e.g. 1, 2 or 6 equation turbulence models) or test data with simulated data and
the importance of a standard post-processing approach.
The reader should understand the data storage requirements and implications, particularly for unsteady
simulations. A separate section may be appropriate for this. Tips on how to reduce large data sets to enable
meaningful interpretation of results would be appropriate.
Furthermore, the book should also briefly cover the main issues which need to be addressed when raw or
processed output must be passed to other analysis software – such as FE packages. Automation of postprocessing, including that required for integration with other analysis types and optimisation techniques
should be included and the risks and benefits of such automation. Guidance on how to pass data beyond the
CFD engineer would also be useful, including pre-processing considerations and checking.
The text should reference and be consistent with other NAFEMS books in the ‘How to….?’ series, in
particular ‘How to Plan a CFD Analysis?’ and the forthcoming ‘How to validate industrial CFD?’ (outline
content can be provided), as well as on-line guidance on Convergence on NAFEMS’ web-site.
The book must be illustrated by examples, ideally taken from a wide range of technology areas; such as
aerospace, automotive, chemical/process, and building services, etc. There must be no bias towards any
particular CFD or visualisation software and both solver integrated and third party post-processors should be
mentioned.
Intended Readership
The book should be applicable to new and improving analysts who perform CFD simulations. It should aim to
give them an understanding of the “whys” as well as describing the “hows” of analysing and processing CFD
results.
The book may also be of interest to technical managers, clients for CFD projects, and regulators, but this is
not the main audience.
Scope
Each proposal should consist of
1.
Scope of document
2.
Chapter headings, possibly with outline contents
3.
Cost
4.
Work plan with target dates / duration
5.
Number of pages (anticipated ot be up to 100)
The authors credentials, curriculum vitae etc
Cost
The cost of preparing each document is expected to be in the low to mid thousands of GB Pounds (or
equivalent in Euros or US dollars as specified).
Submission
If an interested potential author is unable to submit a tender by this date he or she should communicate their
interest to the CFD working group chairman at cfd@nafems.org
Selection
The proposals will be reviewed by the Computational Fluid Dynamics Working Group.