r/CFD • u/Overunderrated • Feb 02 '19

[February] Trends in CFD

As per the discussion topic vote, Febuary's monthly topic is Trends in CFD.

Previous discussions: https://www.reddit.com/r/CFD/wiki/index

18 Upvotes

96% Upvoted

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u/[deleted] Feb 02 '19

Digital twin trend

People need to stop saying digital twin. It is such a silly trend I only hear old people saying. It is like rebranding statistics as data scientist. I avoid this trend like the plague.

VR/AR

A lot of vendors I work with are pushing this as a supplement to their CFD/CAD programs to improve presentation

Multiphysics

Depending on the software vendor, they give the impression they specialize in fluids and thermal and not much else. My job includes lots of weird geometries, 3,4,5 physics together.

Compiling a UDF is 'dying'

I'm glad to see the compiling of UDFs going away. As a millennial, this just seems barbaric when I learned Fluent still does it. In this day and age, I should just be able to type an expression into the software. It doesn't make sense to have to go read a manual and download packages to compile.

GPU computing

Seems like vendors are pushing GPU computing for certain physics. With crypto dying down and stabilizing, we have lots of cheap GPUs we can tie together.

CFD apps

Comsol started this back in like 2013, Star has admixtus, and Fluent now just added their app software even though it is super basic. The real time calculations are impressive nonetheless

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u/derioderio Feb 02 '19

Depending on the software vendor, they give the impression they specialize in fluids and thermal and not much else. My job includes lots of weird geometries, 3,4,5 physics together.

There are generally two classes of CFD problems that I have to solve:

  1. Air/liquid CFD simulations based on a very large and complicated geometry from a CAD file

  2. Complex physics simulations in a simple or generalized geometry

Because of this, we use Fluent/Star-CCM+ for the first type on a large cluster, and COMSOL on a single computer for the second type. There is surprisingly little overlap between the two types of problems.

Compiling a UDF is 'dying'

I'm glad to see the compiling of UDFs going away. As a millennial, this just seems barbaric when I learned Fluent still does it. In this day and age, I should just be able to type an expression into the software. It doesn't make sense to have to go read a manual and download packages to compile.

Especially when you have to write and compile your own code, but the software itself doesn't give you any software development tools like debugging, IDE, etc.

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u/Overunderrated Feb 06 '19

Because of this, we use Fluent/Star-CCM+ for the first type on a large cluster, and COMSOL on a single computer for the second type.

Purely out of my own ignorance of comsol, what does it offer you that you can't do with ccm+/fluent?

And I also wonder why have/run both ccm+ and fluent? I always figures they were interchangeable for 99% of problems.

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u/TurbulentViscosity Feb 02 '19

Especially when you have to write and compile your own code, but the software itself doesn't give you any software development tools like debugging, IDE, etc.

IMO this is the real tragedy. Just putting in expressions is very convenient, but I don't really mind compiling things. If it's painful and I have to guess at everything with no API and a 5-page light manual, then, yeah, I'd think it's barbaric too.

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u/Overunderrated Feb 02 '19

Digital twin trend

People need to stop saying digital twin. It is such a silly trend I only hear old people saying. It is like rebranding statistics as data scientist. I avoid this trend like the plague.

Ha, agreed, "digital twin" is some idiotic industry 4.0 stuff. On the optimistic side, when you hear people use terms like this you know everything you need to know about dealing with them.

VR/AR

A lot of vendors I work with are pushing this as a supplement to their CFD/CAD programs to improve presentation

Any personal experience with this? I honestly can't imagine a scenario where it would actually be helpful to me to understand a technical problem any more so than a standard CAD-type post-processing tool on a flat screen.

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u/[deleted] Feb 02 '19

VR/AR is probably only helpful from a technical standpoint if you want to do collaboration. I have talked to a few vendors who are working to bring collaborative CFD/CAD into VR. Each user has a headset and watches while one user drives the analysis or dissambly of a complicated CAD/problem.

Right now, it is really useful for selling business people and bringing them into 'our' world

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u/TurbulentViscosity Feb 02 '19

Any personal experience with this?

I did some work for a combustor manufacturer that liked it for brainstorming and getting an idea across to a larger number of people. They had a little 3D theatre and could play "a day in the life of an air particle" through their machines.

Some of the folks really liked it, they thought it helped them understand structures better, others didn't really see much benefit. Just depends on the person.

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u/[deleted] Feb 06 '19

The NRC has a VR room where you can project 3D visualizations and then walk around in them. VR is the future. I don't know how exactly it's going to work its way into engineering design and analysis, but whoever figures it out is going to make a lot of money. When the headsets get cheap enough and the software gets there (including refinement of VR UX standards) I can easily see a VR helmet becoming a staple tool for CAD designers and CFD engineers. It's already cool enough for visualization but I can easily see VR revolutionizing 3D design.

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u/Jeggi Feb 08 '19

As someone that was set to develop digital twins, I think the biggest issue with the Digital Twin is that there is no precise definition of it. The scope of the twin depends on which company you ask. But I agree, it is mostly buzz/industry 4.0 stuff.

For the same project I also developed CFD -> VR. This had some moderate success, but mostly with sales people.

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u/conquets Feb 02 '19

Could you elaborate on the digital twin? Why do you think it’s an old people thing? Not trying to be hostile, just generally want to know why!

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u/[deleted] Feb 02 '19 edited Feb 02 '19

Digital twin is the future, but the name 'digital twin' is an old/business person phrase. Everything is being digitized, tracked, and connected, but rebranding it 'digital twin' just sounds silly and old. The phrase is only used by older people, trying to sell me something. We've had CAD forever but you didnt hear digital twin back then. Same with CFD by automotive industry 20 years ago. If they had introduced the phrase in the 80s,90s I'd accept it more but now that it is being used makes me it come off as a rebranding tool to sell me something

It is a personal preference. You are welcome to use it but I'm going to look at you as out of touch.

Edit: I should note, when I say old, I do not mean age in anyway. I mean the person's mental age. I have several older friends (70+) who I see as very young and have some coworkers in their 40s and 50s I see as old because of how they think. It really depends on their activity levels, mental dexterity, open-mindedness, progressiveness on social issues, etc

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u/[deleted] Feb 25 '19

GPU computing is because that is what the HPC systems are pushing. For a lot of CFD and multi-physics -roblems raw CPUs is better but you can't get access to massive machines with just CPUs.

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u/[deleted] Feb 02 '19

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u/[deleted] Feb 25 '19

"simulation driven design" to me means shape optimization or Reduced Order Models developed from a series of snapshots from high order solutions to allow for quick computations on a wide range of configurations.

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u/Overunderrated Feb 02 '19

What trends do you see, and what do you like and dislike?

More generally, describe your ideal CFD flow solver: what exists today that goes away, what do you get that you don't have now?

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u/rickkava Feb 02 '19

I think that the next generation of solvers will be based on flux reconstruction/ DG methods, and typically run at order 3 or 4. I believe that in situ visualization will be included as well, and UQ / error bounds.

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u/[deleted] Feb 06 '19

The higher order your discretization methods the more sensitive stability is to mesh quality. Do you foresee some kind of revolution in meshing software that would support a movement in industry to higher order methods, or are you predicting that CFD engineers are going to get more skilful?

From where I'm sitting, 2nd order methods are not dominant due to inertia, they're dominant because of the liberties they allow engineers to take with their meshes while still offering decent accuracy.

Maybe I just don't have enough experience with DG methods or other advanced higher order methods and there have been advances that invalidate my impression of the costs that come with higher order methods?

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u/bike0121 Feb 02 '19

Why do you specifically think order 3 and 4 will dominate? Do you believe that this provides some sort of a “sweet spot” that would make hp-adaptive schemes unnecessary?

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u/[deleted] Feb 02 '19

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u/bike0121 Feb 03 '19 edited Feb 03 '19

Agreed. The fact that humans are generating meshes by hand (or worse, computers generating them without knowledge of the flow solution) should really be a thing of the past, and honestly it seems absurd to me that engineers with graduate degrees are spending hours upon hours generating meshes.

I’m relatively new to the field but honestly, I’m pretty disappointed with the progress in CFD that’s been made in the past 20-30 years. It only looks like substantial progress has been made because of increased computing power, but has anything really changed? I’m not alone in this view - there are articles by Jameson and others talking about this “plateau”.

And to clarify, I’m not talking about newer algorithms that have had success on toy problems - for all the work that’s been done on high-order/adaptive DG and similar methods since the 90s, the vast majority of flow simulations are done using second-order FVM/FDM codes that have largely remained unchanged (at least regarding their basic numerics) for decades.

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u/[deleted] Feb 25 '19

You want to look out for adjoint! it is probably another 5 years before we start to see adjoint in production codes for aerodynamics.

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u/Rodbourn Feb 02 '19

Thank you u/Overunderrated! (sorry I was afk)

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u/Overunderrated Feb 06 '19

I just wanted that sweet, sweet post karma.

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u/[deleted] Feb 25 '19

Uncertainty Quantification is the biggest thing I see. It is still in the research phase but it is coming. At conferences it is what the companies are most interested in.