David Tatchell’s Blog

Reflections on experiences and lessons learned during 40 years in the CFD business. Thoughts on the present state of the CFD industry and future trends, in the broader context of the CAE, CAD and EDA industries.

6 January, 2010
To complete my recollections of the time when I was working on my PhD at Imperial College during 1969-1972 …
 
First of all, a short theoretical interlude. As CFD theorists know, it is often useful to categorise classes of flow according to the form of the governing equations – as parabolic, hyperbolic, or elliptic. Leaving aside hyperbolic – supersonic – flows – I want to focus on the distinction between parabolic or elliptic flows as applied to low-speed subsonic flows. 

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2 November, 2009
In previous blogs in this series I have recounted my recollections of the first development of 3D CFD methods at Imperial College in the very early 1970s – and how, after a “false start” with the SIVA algorithm, I adopted Suhas Patankar’s SIMPLE algorithm (with a refinement of my own) for my PhD work.
 
As will have been apparent from the earlier blogs, the main focus of the 3D Boundary Layer Group, of which I was part, had been on developing the numerical methods and algorithms themselves – leading to the successful application of SIMPLE to a range of laminar flow situations, including my own work on developing flows in square and rectangular sectioned ducts. But of course, as we all know, this only takes us part way towards a practical CFD solution for real engineering flows – there is still the troublesome matter of turbulence modelling!
 

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30 September, 2009
A bit of light relief a couple of weeks ago – I took my aging Porsche to the Goodwood race circuit for a Porsche Club Track Day. (For aficionados – she’s a 1990 911/964 Carrera 2 Targa – completely standard spec, but quite fast enough for me!)
 
Track days are great fun – a chance to drive your car in ways that would not be prudent, or legal, on the public roads – and to begin to get a feel for what real motor racing must feel like. As I say – great fun! 

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21 September, 2009
I should add a word or two to my previous blog – “CFD … Or Not CFD”.
 
What does all this mean for the CFD itself? Does the self-perception at Flomerics that “we are not a CFD company” mean that the CFD itself is less important or gets less attention? Absolutely not! Actually the opposite is the case. One of our fundamental requirements has always been that the software can be used effectively by users without any CFD knowledge or expertise. This then leads to some very special challenges associated with the CFD itself.

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8 September, 2009

I started off this series of blogs by claiming “40 years in CFD” – which is true.

It’s therefore a little ironic that when we were setting up Flomerics 20 years or so ago, we made a point of emphasising to ourselves that “we are not a CFD company” – to the extent that, some years later, when we were included in industry rankings of CFD companies, we weren’t sure whether to be pleased at a favourable ranking, or displeased that we were included in the list at all!

This isn’t as perverse as it may seem. Let me try to explain. Read the rest of this entry »

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21 August, 2009
In my last blog I explained how Suhas Patankar created the SIMPLE algorithm in 1970, and how the 3D Boundary Layer Group at Imperial College then adopted SIMPLE for all its future work.
 
I first applied SIMPLE to the problem that I had been working on with the SIVA method – laminar flow in the inlet region of a rectangular- (mainly square-) sectioned duct. This led me to identify some deficiencies in SIMPLE in its standard form, and to devise an improved formulation.

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13 August, 2009
In the first blog in this series I described how the research group at Imperial College, under Professor Spalding, on computational methods for 3D parabolic boundary-layer flows (the “3D Boundary Layer Group”) got started, with me as a relatively junior member. I described how I (re)discovered the need to use a staggered grid when solving for the primitive variables, (pressure and velocities) – and how Suhas Patankar joined the group around mid 1970.
 
To continue …

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4 August, 2009
I just want to make a brief response to John Parry’s recent blog  in which he challenged my ability to remember the 1960s.

It is said that everyone who was around at the time remembers where they were when President Kennedy was assassinated. I have for a long time had a vivid memory of coming home from a Beatles concert (I only ever attended the one) to find my parents watching the TV coverage of the aftermath of the Kennedy assassination. Then, over the years I began to question the memory. Maybe I was combining two vivid memories of formative events in my teenage years into one, convenient, composite memory. A trick of the mind perhaps. Over time I concluded that this was the case – I did see the Beatles, and I did watch coverage of the Kennedy assassination on TV, but not the same evening. Read the rest of this entry »