Zoom-Webinar: My “Recipe” for learning How to Become a CFD Self Sustaining Practitioner (Nov. 2020) + Unabridged Recording

I’ve been practicing CFD for the past 15 years. I started practicing at my second year of undergraduate studies at Tel-Aviv University, as the stars aligned for me, and a childhood very close friend of my dad, who was also a faculty senior Professor by the name of Moshe Rosenfeld, head of the faculty’s CFD LAB, and a very experienced Fluent practitioner (that was before ANSYS acquiring Fluent), took me under his wing and offered me to start working at my spare time at the CFD LAB (I guess the incentive was my dear dad, he’s close childhood and still one of his best friends. Certainly not my beautiful eyes…).

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Wolfson Building – Where it all started

I was also lucky enough for the Professor to not only give me little chores, and although my knowledge in fluid dynamics as a second year undergraduate student at the early stages of even taking some fluids 101 courses, was for every meaningful purpose close to nonexistent, he always seem to take the time explaining carefully what it is I’m actually doing. He also gave me a library card allowing a free access to a top-notch of technology machine called “a copying machine”, hence after taking the time to fully explain what we are aiming for I would run to the library (just over the bridge), copying the relevant references he was sure to mention, and read…. of course I had so much basic knowledge missing, I couldn’t really make sense of what I’m reading (although his office explanations of the phenomenological CFD application were handling was wholeheartedly sincere and elaborated), I quickly took note that I simply miss the basic knowledge… But then there’s the university  engineering library, with all the books in hard copy fashion, so I simply decided to start from the beginning: fluids 101, discretisation schemes, boundary layers and turbulence (schlichting-pope-tennekes lumley-Chorin’s random walks…Ahhhh….), Oh, transition – got me hooked on KTH’s Dan Henningson team, then pure CFD (structured pde methods, unstructured methodologies, pde solving ) – got me accidentally to a set of lecture notes by a mathematician named J.M. McDonough, who seemed to want to cover many of the topics I was just on the need for: incompressible flows (methods, got acquainted with this professor Patankar guy… Solving PDEs: Jacobi, SOR, ADI, ILU, Multigrid, marching methods, Domain decomposition, Newton-Kantorovich, d&g, Cell Reynolds/Peclet…). He also wrote about Turbulence, funny to say as somewhat of an opposer to statistical methods such as RANS, it is turbulence from a mathematician standpoint (get all of his lectures here. I mean really, download all of them now)

In the lab getting wonderful cfd explanations from the Moshe, than doing my job which was mostly enclosing a vortex, get the value for the circulation and c&p to an excel worksheet, then repeat…

But something happened on this weird road, not really a CFD practitioner yet, reading every book I could lay my hand on, and while doing that for a long time I new already what’s “the good stuff”, I knew it! I shall be practicing CFD for a long long time now!!

Time came for some more software experience, it was wonderful. I kind of felt well acquainted with the GUI from the circulation calculations, but till then didn’t do much else, so I took a CFD course, yet something in me was different while doing the tutorials… everything was knew in perception, first time I did what the tutorial told me, the nice colourful pictures where there, but something else was happening also dazzling me… there were my library friends: types of meshes, Boussinesq hypotheses, the law of the wall, the “viscous button” also had some other friends I knew all about: Here’s Spalart and Almaras, I know exactly what they are there for, here’s Wilcox’s k-w, there’s the BSL, it combines smoothly two models, here are the k-epsilon’s family, I know why there’s a wall treatment window added to it.McDonough and Menter explained it perfectly. Then there’s the kr-w SST,I remember this one from Menter’s 92 NASA publication, it got me reminded of Bradshaw, that beyond his hypothesis that makes the model somewhat improved over the BSL for “regular” aerodynamics, had quite interesting contributions.

I felt a little weird following the instructor, a graduate MSc soon, because I knew our boundary layer for the simulation was not covering the entire log layer. I’ve checked the Eddy viscosity ratio. But he said that’s the tutorial, the mesh was already prepared, and anyway, he doesn’t know what I mean by log layer and how can I decide that just from looking at the mesh, that he’s colleague, made a mistake. So modesty I said, that I’m sorry, that maybe that’s what they want us to see in the simulation but still as it happens, if the choice is to compare the SST with the standard k-e for such a low Reynolds flow and with the use of standard wall functions will perform badly, it’s a shame that the SST can’t give the good numbers for the drag force just because the boundary layer thickness larger what the prismatic cells cover, especially as he gave an experimental result to be compared to … but then, I can repeat the simulation while taking a break from circling a vortex and c&p the resulting circulation to excel and repeat the CFD and also get some more experience at calculating boundary layers, doing that eddy viscosity ratio checkup and see whether I get a better fit. Moshe wouldn’t mind…

As far as I know, many undergraduate “CFD” courses are still awful (in comparison to the ANSYS learning hub let’s say…). And CFD is a lot more then getting a converged solution…

 

I get many, and I mean many guidance requests. I do like to help, I can spend a lot of rime helping students of any kind (undergraduates, graduates, doctorate, lecturers). I’m not a saint, I enjoy it. I seem to get in a state of Flow (the Mihaly Csikszentmihaly kind of Flow). 
But time is not an inexhaustible resource. Many questions I would have liked to spend hours on explaining to a person eager and passionate to learn are lost. Notwithstanding the fact that most of those who actually can help would not give it even the slightest time. For them there is nothing gained. That’s sad, but true:

4 thoughts on “Zoom-Webinar: My “Recipe” for learning How to Become a CFD Self Sustaining Practitioner (Nov. 2020) + Unabridged Recording

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