[Avr.Tomer]

Can we actually determine which turbulence model is the most valuable to the many engineering applications we have?...

Could modeling error due to different types of turbulence closure models, and by that, our choice of turbulence model be different even in different parts of a domain for a specific application?...

Does the abundance of turbulence modeling choices produce a noticeable engineering value?…

Some models portray to include “more physics”, whether it’s RANS transition modeling approaches, Scale-Adaptive simulation (SAS), and hybrid RANS/LES. Is that consistently so from an engineering value standpoint?...

Do we even know enough about complex phenomena such as the transition from laminar to turbulent regimes to incorporate them in a simplistic and limited in it’s range of applicability framework, such as RANS?...

Spoiler Alert: The following questions do not have answers in this new "All About CFD..." post. Just my thoughts...

What are your thoughts?

https://lnkd.in/dkKqUcz

[sbaffini]

You touch a very interesting point, engineering value. I think we don't even have a precise framework to actually evaluate the engineering value in CFD as a whole.

However, before I attempt any answer (which will take me some time), let me add that in my opinion, to a large extent, the value of any turbulence model cannot be evaluated without also referring to its implementation in a code.

I understand the point of view of assimilating the availability of a turbulence model in some code on the same level of, say, the availability of Sutherland law for viscosity, but that really isn't the reality.

From this point of view, for example, Spalart-Allmaras wins hands-down at any comparison, from every engineering point of view.

Take any other model and you won't find two equal implementations.

[FMDenaro]

Originally Posted by Avr.Tomer

Can we actually determine which turbulence model is the most valuable to the many engineering applications we have?...

Could modeling error due to different types of turbulence closure models, and by that, our choice of turbulence model be different even in different parts of a domain for a specific application?...

Does the abundance of turbulence modeling choices produce a noticeable engineering value?…

Some models portray to include “more physics”, whether it’s RANS transition modeling approaches, Scale-Adaptive simulation (SAS), and hybrid RANS/LES. Is that consistently so from an engineering value standpoint?...

Do we even know enough about complex phenomena such as the transition from laminar to turbulent regimes to incorporate them in a simplistic and limited in it’s range of applicability framework, such as RANS?...

Spoiler Alert: The following questions do not have answers in this new "All About CFD..." post. Just my thoughts...

What are your thoughts?

https://lnkd.in/dkKqUcz

To be honest, my answer is ... no. I don't think that the RANS formulation has the intrinsic idea of describing transition, any turbulence model you could immagine.

[Avr.Tomer]

Originally Posted by FMDenaro

To be honest, my answer is ... no. I don't think that the RANS formulation has the intrinsic idea of describing transition, any turbulence model you could immagine.

I agree. I go even further and claim that I'm not sure the CFD practitioners are doing enough to fully understand these models and their range of applicability (or lack there of) , therefore not able to put a quantifiable measure on the engineering value of them, while commercial code vendors seem to have found that merely presenting an exhaustive list of models and variants does a good enough job at convincing the average practitioner in the unsupported claim that more physics of engineering value is captured.

[JBeilke]

Originally Posted by Avr.Tomer

... that I'm not sure the CFD practitioners are doing enough to fully understand these models

Who are "the CFD practitioners"?

[FMDenaro]

Originally Posted by JBeilke

Who are "the CFD practitioners"?

well, that's a term for denoting generic users of commercial CFD softwares with no specific background in CFD theory and newbye in the field.

[JBeilke]

Originally Posted by FMDenaro

well, that's a term for denoting generic users of commercial CFD softwares with no specific background in CFD theory and newbye in the field.

Very precise definition. That's a good basis for a scientific discussion.

[Avr.Tomer]

Originally Posted by JBeilke

Who are "the CFD practitioners"?

On average it's engineers practicing CFD on a regular basis...

[JBeilke]

Originally Posted by Avr.Tomer

On average it's engineers practicing CFD on a regular basis...

"On average, the village pond is a meter deep and yet the cow is drowned."

[Avr.Tomer]

Originally Posted by JBeilke

"On average, the village pond is a meter deep and yet the cow is drowned."

I find the character of most CFD practitioners to be concentrated mostly around what I deemed average. There are exceptional outliers, but I feel that it is not the outliers who set the tone for claims along the line I have presented in my blog post. This worries me in the kind of ways I have elaborated on in my post, especially regarding the engineering community.

On a different note, I don't feel I would like to have a 'Twitter-like" discussion. I can not disagree with someone, nor can I update the prior credence I gave to my claims in a discussion with someone who I think is not even wrong for not making a point