OpenFOAM vs. Fluent & CFX
 

RANS modelling had its days and now LES is taking over. CFX is not a very good software for serious LES work. I am not so sure about Fluent. Considering the cost and limited features that CFX and Fluent offer, is it still worth to work on such softwares?

On the other hand OpenFOAM offers much more than CFX for both RANS and LES modelling and its absolutely free of charge. OpenFOAM results have proven to be much more accuarte than other commerical codes. When OpenFOAM is the future then why work on CFX and Fluent. Why are you guys still using CFX and Fluent and have you considered switching to OpenFOAM? Comment please

Re: OpenFOAM vs. Fluent & CFX
 

Dear Marco,

You got to be kidding!! right?

OpenFoam with all the good stuff it might have is not even closed to be a full featured product for industrial use. It cannot be compared with any of the 3 major CFD codes: FLUENT, CFX or STAR-CD. Not even to smaller codes such a CFD-ACE, CFD-Design, etc.

You want to tinker with the code, fine. That is your choice to enjoy. Other people have real targets to obtain a solution on a given problem and do not have the time to play with someone else's code.

Have a nice weekend.

Opaque

Re: OpenFOAM vs. Fluent & CFX
 

Hi opaque

I dont know what made you say that OpenFOAM is not ready for industrial use. As far as i know most of the universities and research organistaions are already switching to OpenFOAM due to its accuracy and reliability. OpenFOAM is an open source code and we can amend what we like in it even build our own solvers. I consider it advantage not disadvantage!

OpenFOAM is not some one else's code, its everyone's code. Any one can install it for free and it will give you better results than any other commercial code. I will post here comparative studies conducted between OpenFoam and other codes, then you can make your mind up.

You too have a nice week end opaque.

Re: OpenFOAM vs. Fluent & CFX
 

Hello Marco,

What can you say about the order of accuracy of the solver ? I'm not sure but I understand that the discretization in OpenFoam is only second order ... in Fluent 6.3 you could use third order.

I'm interested in a fair comparation between Fluent and OpenFoam.

Re: OpenFOAM vs. Fluent & CFX
 

Dear Opaque,

It is quite clear that you haven't even tried running OpenFOAM, let alone run some serious comparative tests. My company supports a number of commercial clients switching their CFD from CFX, Fluent and STAR-CD to OpenFOAM and they are most certainly not kidding.

I have worked both at CD-adapco and Fluent during my career and know my CFD pretty thoroughly, so the statements like "real targets to obtain a solution on a given problem" and "playing with someone else's code" are way off the mark. Why don't you join us at the Third OpenFOAM Workship in Milan in July and come see for yourself what the fuss is about.

Sincerely,

Hrvoje Jasak, OpenFOAM developer

Re: OpenFOAM vs. Fluent & CFX
 

The very first starting point is about LES for industrial applications. Sorry, this is not the case for 99.9% of the industrial requirements on restitution time.

The second point is about LES in itself. LES does not consist barely in putting a sub-grid scale model. If a significant part of the inertial scales of the turbulence spectra is not really solved based on a filtered approach for the smallest scales, please do not call it LES. You can call it whatever you want, but LES with dissipative and dispersive schemes, on URANS meshes with URANS times steps, just using a sub-grid scale model instead of baseline RANS one is definitely not a LES to me. Some may smile, but I see more and more industrial work of the kind.

Re: OpenFOAM vs. Fluent & CFX
 

Your statement seems to indicate that there are people who are shifting from CFX fluent etc to openFOAM for the reasons that openFOAM provides something that these softwares do not provide. Which is entirely wrong. As you said you have worked both as fluent and at starCD then you know very well that these commercial software provide a lot more features that openFOAM do not provide.

Of course this all costs. And people do pay for features.

If there are people who are switching from CFX and Fluent to openFOAM the reason certainly is not that openFOAM is superior. It may be anything but not this.

Re: OpenFOAM vs. Fluent & CFX
 

Hi, Hrvoje,

OpenFoam is indeed powerful and goes to outperform others.

But just a aquestion:

Since you be consultant of some commercial company like Fluent, you know more about their internal structure, based on my understanding from Fluent (its UDF capability) it should be written in C and is not object-oriented, i guess to keeping performance, So what about performance of OpenFoam in contrast with Fluent on a same problem?

Two suggections:

1) as you see most concern of CFD users are pre-processing and particularly grid generation, I suggest to add a octree cartesian cut cell grid generator in OpenFoam (is fully automatic for health CAD file) and adding a class to support such grid (is quit simple, each cartesain cell, either formal or cutted is a polyhedron). Whit this feature a great degree of automation is added and you could draws attention of cartesain (immersed boundary) too.

(Of course such grid is not very suitable for viscus flow, but cover a wide range of applications)

2) portability of OpenFoam is still issue, if you enquiry about some end-CFD users a wide variaty of them use windows as promary OS, while OF does not compile under native windows compiler, i guess under cygwin is possible (not sure), but this is not a clean way and also, under cygwin performance is decreased (anout 40 % in CFD codes, my experience)

What you think?

-John.

Re: OpenFOAM vs. Fluent & CFX
 

Babu i agree with you URANS is not LES. As the speed of computers get faster there is definite shift from traditional RANS to LES. My point was that CFX as it stands today is not very good for serious LES work.

John it does not cost you anything to make a shift from Windows to Linux. Again, linux open source OS is better than windows it terms of performance. Then why not make a shift to Linux and OpenFOAM and destroy these money making monsters. Comparative studies between OpenFOAM and other commercial codes will follow soon.

marco

Re: OpenFOAM vs. Fluent & CFX
 

> My point was that CFX as it stands today is not very good for serious LES work

Note that LES is state-of-the-art and it is too soon to add LES as a feature in commersial pakeges (commercial packeges use mature and reliable models, their users do not know state-of-the-art by default). Also power of current computers are beyound to perform a LES (considering real scales) simulation of industarial application. Else adding LES model to a commercial pakceges is not a difficult task. e.g. you could easily add explicit SMAGORINSKY filter by a UFD or such tool to any laminar solver.

But, I think It is a silly comparision if someone try to compare a commersial packages with an open-sources, because we look for open-source to do a research on cutting edge which is not possible for commercial ones. So OpenFoam has its specific position without attention to its limitation in contrast.

> John it does not cost you anything to make a shift from Windows to Linux.

so you do not understand what i imply !

> Again, linux open source OS is better than windows it terms of performance

are you sure? googling on this issue does not give a sharp judge !

PS: do you modify linux's kernel sofar, that talk about its open-source benefit? do you have ability of this job?

Re: OpenFOAM vs. Fluent & CFX
 

Dear Dr. Jasak,

I just could not believe what Marco said, but it seems those supporting/developing OpenFoam are reading beyond what is written.

I said: "OpenFoam with all the good stuff it might have is not even closed to be a full featured product for industrial use". Is it? let us review it:

a - Geometry enviroment: I do not think so.

b - CAD import: what CAD formats does it support? None.

c - Meshing in OpenFoam: it does not qualify to be compared to any decent commercial product in the CFD, FEA or even plain meshing market. You read the messages in the OF forum and cfd-online, and even OF supporters are asking for decent meshing of complex geometries.

d - Physics pre-processing: can OF be used in a modern design environment along those like CFX, FLUENT, CCM, CFD-Design, etc? I do not think so.

e - Post-processing: it does not even has its own, but relies on Paraview. Can it do quantitative post-processing for common modeling applications, simulation reports?

f - Physical models: Yes, there are a bunch of them in the source packages, but I have not seen any resembling:

- Radiation: surface to surface modeling, discrete ordinates, or Monte Carlo for starters. What about non-gray media modeling? None to be seen that compares to either FLUENT, CFX, or STAR-CD

- Combustion: Yes, it has some simple mixture fraction based models, but where are flamelets, ISAT, EDC, of ECFM?

- Turbulence: that is probably the one with several implementations; however, not even close to the pletora of models you will find on commercial codes. LES is not state of the art as Marco called. It is a fashionable model just because the computers are faster these days. The concept is more than 40 years old, and it is just receiving more attention lately.

- MHD: no comment. You know that the implementation there is barely a try-out of some good ideas. But, it will require considerable validation to be used by experts in the area.

- Stress modeling: well, I leave that for the FEA guys to evaluate.

Should I continue? Was I way off the mark? No, I was exactly on the mark. CFX, FLUENT, STAR-CD are not just a solver, they are professional tools that try to cover the whole process (geom, cad, mesh, pre, solver, post) to address more than just a limited set of problems.

I never even touched the issue of the core solver, numerics, speed, robustness, etc.

Now to your response,

I skimmed through your thesis once, read some of your papers (as well as Weller's). I know about your expertise in the area. I have no basis to question it. However, I had higher expectations of the source packages after reading the seminal paper :

Weller, H.G.; Tabor G.; Jasak, H. and Fureby, C.: A Tensorial Approach to CFD using Object Orientated Techniques, Computers in Physics, 1998 v 12 n 6, pp 620 - 631

- Have I run OF? No need. I have CFX and FLUENT at my disposal.

- Do I know what the fuss is about? Yes I do. Good papers, good simulations, a lot of color too. I can also get a Wii, or PS3, or XBOX-360 to play. The "target" I refer to is to finish the problem at hand: modeling a device and obtain enough physical insight to make improvements. Improving the modeling tool (regardless of how good it is) is an expensive distraction for some companies.

- You said "My company supports a number of commercial clients switching their CFD from CFX, Fluent and STAR-CD to OpenFOAM", and later added "I have worked both at CD-adapco and Fluent during my career ..." Hopefully, the time frame while you supported your clients to migrate away from FLUENT /CD-Adapco never overlapped with the time frame you worked at FLUENT or CD-Adapco. That is called a conflict of interest in professional ethics.

Hopefully, my view is clear this time.

Sincerely,

Opaque

Sorry, I do sign personally. However, those in the forum already know I work for a commercial CFD vendor.

Re: OpenFOAM vs. Fluent & CFX
 

Opaque,

I think that comparison is not feasible as others say.

But most of ur critsism is on pre/post process,

Post process: is not very important!, when a top graphic team (kitware) develop an open post-processor for ours, why we look for own post-processor. We just should costomize its.

Pre-process: I do not think your mentioned packages has a good pre-processor, e.g. Gambit of fluent has a very weack CAD media and also its grid generator has its own flaw. There are a veriaty of specific preprocessors that we could rely on them: GID, Patran.

Processor: althouth commercial vendors claim some features but they have their own limitations, particularly for multi-physics simulations, e.g. in my experience with Fluent 6.0 its VOF option (free surface flow) did not couple with phase change option (to simulate casting process). It seems that handling multi-physics simulation is an outstanding feature of OpenFoam.

What about optimal control and design optimization which is one goal of CFD analysis. Do your mentioned commercail packages have such option, i do not think, at least for Fluent, but for an opensource we could implement its.

Re: OpenFOAM vs. Fluent & CFX
 

The most balanced post so far, it does not mean That I agree with all your comments, but the one that is 100% true is that "CFX, FLUENT, STAR-CD are not just a solver, they are professional tools that try to cover the whole process (geom, cad, mesh, pre, solver, post)" That is it. As for the rest of your comments, just one thing to mention, OpenFoam source code is available and a qualified user can add whatever he believes is missing.

Re: OpenFOAM vs. Fluent & CFX
 

Post process: is not very important!, when a top graphic team (kitware) develop an open post-processor for ours, why we look for own post-processor. We just should costomize its.

post process and preprocess are very important and integral part of analysis. As far as paraview is concerned (this is my personal view) that it is just a joke on the name of post processing. On my windows machine that has 3gb plus RAM I could not read a results file with say 1 million cells in it. On the same machine I could easily read 6 million cell's results on fieldview. No problems. Paraview is just meaningless for serious work. I find it funny that you find gambit very bad but very happy with paraview.

Gambit of fluent has a very weack CAD media and also its grid generator has its own flaw. what serious flaws you are talking about in gambit. CAD handling was bad, and it has been improved. In my more than 5 years of use of Gambit I never had any problems due to it though. As far as meshing goes, gambit is one beautiful. It is difficult to use for people who do not understand how to work with it. Those who understand like me, its their first choice.

Now lets take solver,about which you seems to be so sure

Fluent provides: pressure based segregated solver pressure based coupled solver density based coupled solver (these are major types of solvers we know)

Further OP and Fluent both provide algebraic multigrid. But where is Full multigrid option in OP. And there are many many things.

Really comparing OP to Fluent is just insult to a full fledged solver. (I am not adding the stablity and speed of solution on Fluent).

Re: OpenFOAM vs. Fluent & CFX
 

I think OPenFoam can only focus itself on academic purpose because it is open. It is never possible for openfoam to compete itself with commercial packages. If you do not agree with me, please try to check the following items in both openmfoam and commercial packages:

1)easier to use

2)easier to analyze simulation outputs

3)portable

4)have an obvious improvement in accuracies

5)much faster?

6) have much priority in handling industrial scale calculations?

7) have more physical models?

8)have some special models which others do not have

Unfortunately,in all above items I can not see openfoam has a positive position. I found that most applications of openfoam had been mainly conducted by some academics and the developers themselves. No big company want to buy a people to learn and use a complicated code. This is a dangerous thing as the the use of openfoam requires too much experience and time, and only works well in Linux or the like. Looking at our world, how many companies which are using Linux based OS in their workshop are there? More importantly when we operate a company, we hope our things are standard and can be quickly controlled by new guys. Or we have to spend extra money to keep the positions for experts. So the use of openfoam may cause more money in a long-term view.

On the other hand, at this stage if some software says it can solve single phase fluid flow in complex geometries or the like with good accuracies, it sounds really ridiculous. It is because most commercial packages can do it. These are the basic functions of CFD. BTW: When Openfoam users claim that Openfoam has advantages over the existing commercial codes in some aspects, will you please to tell me the reason and which advancing modes or numerical techniques make this work. Now let's look at one of the biggest applications of CFD: the so-called process and chemical industries. Here the multiphsics and multiphase flows are our targets. OpenmFoam seems like a package mainly applicable to these places. However, Openfoam is really poor at this point. It have no new models in handling multiphase flow and combustions etc. the physical models available can be ignored compared to Fluents etc.

At last I want to say, Openmfom has made a great contribution to push CFD package to walk toward correct direction. We need to elaborate our simulations by introducing some new modes. The "black" commercial packages make this quite difficult, even a simple modification. Even worse, some packages cheat us in order to let results looks good. Openmfoam has no such problem. If the developers try to make it easier for new guys, it will be very good to the whole community of CFD. Now the problem if the developers work in this way, who are willing to support them?

Cheers,

Chen

Re: OpenFOAM vs. Fluent & CFX
 

I do not like elongate this disscusion, becasue i basically belive it is not feasible to compare opensource with commersial package,

> As far as paraview is concerned (this is my personal view) that it is just a joke on the name of post processing.

silly sound, so you do not have idea about what you say :)

i think your comparision be not equivalent or you do not know how to use paraview, how to write data and manipulate them (of course PV is not user friendly) i have used it on my PC with 2.5 G for more than 5 M unstrutured grid without any memory problem, after suitable filtering its rendering speed is comparable with Tecplot 10 (is fairly fast)

Re: OpenFOAM vs. Fluent & CFX
 

Of course you do not want to elongate discussion because you have nothing to support to what you say that openFOAM and Fluent should be compared as solver and I tell you that openFOAM only provides fraction of what Fluent provides.

You did not come and tell me that OpenFOAM has Full Multigrid Algorithm for difficult problems. You did not tell me that OP can give me coupled solvers. You did not provide any proof that OP converges faster than Fluent and is more accurate.

Fluent and other commercial solvers provide much more features, this is a fact. Deal with it.

Of course you do not want to elongate the discussion. I can understand.

Now as far as Paraview is concerned, last time I checked it had lots of issues with Polyhedral handling and it is well documented.

I do not know how you would assume that I would keep banging my head with something like Paraview when I can do my work with Fluent's post processor. I gave up on it long back and that time it did not read 1 million cells. But to check the things again I will again download and give it a try. And yes, I would use ensight file written by Fluent. Lets see.

Re: OpenFOAM vs. Fluent & CFX
 

Marco, let me give you a data point here. I am a single-person consultancy. Every time I use commercial software, I have to pay for it out of my own pocket, it has a direct impact on how profitable my business is. I have also, sporadically, over the last few years, experimented with OpenFOAM.

So here is what I do. For commercial work, I use commercial codes. Every hour I spend experimenting with OpenFOAM is time I could be using to generate revenue. OpenFOAM is a fine piece of work, but when you have to answer somebody's design question quickly, you don't have time to mess about. There have been times when I could perhaps have used OpenFOAM's solvers, but I still needed commercial tools for meshing. Likewise, Paraview is a wonderful piece of software, and I use it nearly every day, but there are things (such as quantitative post-processing) that standard Paraview cannot do. Sure, with some user programming, one could perhaps extract the necessary numbers with Paraview, but my client does not pay me to sit and figure out how Paraview works.

I am very keen to see more use being made of OpenFOAM and other open-source codes, but to even suggest that users should ditch their current codes overnight in favour of OpenFOAM is just amazingly naive. When you start dealing with real-world engineering design problems, one of the things you really need is good documentation about the code and its features. The detail documentation for OpenFOAM just isn't there. This is not a criticism of OpenFOAM, after all, writing documentation is a huge expense, and nobody is paying the code developers to do that.

I have nothing but admiration for the OpenFOAM guys, but outside of academia, the license cost savings rapidly disappear when you need to do real work in a hurry.

Re: OpenFOAM vs. Fluent & CFX
 

I thought opemfoam was free up to a point (limited use) and then it was charged. Isn't that the case?

Re: OpenFOAM vs. Fluent & CFX
 

No thats definitely wrong. OpenFOAM is open source software.

Re: OpenFOAM vs. Fluent & CFX
 

I think Charles summed it all up. For academic world OpenFOAM is indeed much better software than other commercial CFD codes. As a research student i am not aware of problems that you guys face in industry. Yes, OpenFOAM has its drawbacks like CAD, meshing etc but at the end of day its absolutely free software and it is improving rapidly. Therefore i am of the opinion that OpenFOAM will eventually take over commerical CFD codes. When OpenFOAM is future then it is better for a research student like myself to stick with it.

Marco

Re: OpenFOAM vs. Fluent & CFX
 

>>Yes, OpenFOAM has its drawbacks like CAD, meshing etc but at the end of day its absolutely free software and it is improving rapidly. Therefore i am of the opinion that OpenFOAM will eventually take over commerical CFD codes.

That is some logic - OpenFOAM is improving rapidly while commercial codes are freezing up like ice. I think your position as a graduate student shades your views.

W.

Re: OpenFOAM vs. Fluent & CFX
 

As a research student, if you can not get help from your pioneers in the use of openfoam, I think you never try it. It just wastes your time. Please note that almost all techniques in openfaom has been well developed to some extent. What it is your originality in your research? You may say I focus the process not modelling. In this case, why not directly use commercial packages. you may gain more if your time for the study of openfoam has been utilized in your research. However, in a long-term view, your research group can try to replace commercial packages with openfoam. In one word, try to work on openfoam together with others for research purpose, otherwise just forget it.

Re: OpenFOAM vs. Fluent & CFX
 

"are you sure? googling on this issue does not give a sharp judge !"

That's just microsoft marketing and has little to do with the truth. If the microsoft OS is so good why is it that all high end workstations and supercomputers use linux or some other flavour of unix? Actually the google servers all run linux (as do amazon).

Re: OpenFOAM vs. Fluent & CFX
 

Although I agree with you Tom (regarding win vs Linux), that type of "logic" is somewhat dangerous. You can just as easily turn the argument around and say that because XX% use windows it is superior to Linux.

Similar logic:

"Hundred billion flies can not be wrong - eat shit."

=)

Re: OpenFOAM vs. Fluent & CFX
 

It's a good idea actually to test the CFD performance before making big claims about differences in performance between Linux & Windows. There are some good reasons to use Linux for CFD, such as:

Cheaper and easier to set up a cluster

64-bit Linux is now very mature and quite well-supported in terms of drivers, etc., compared to 64-bit Windows XP, where there is an astonishing lack of suitable drivers for some hardware

64-bit Windows versions of most commercial CFD codes only came out several years after the 64-bit Linux versions.

Some software, such as OpenFOAM, won't run under Windows. Other useful software, such as Rhino, Multisurf and Excel, won't run under Linux. (and no, OpenOffice is a very good alternative to the other elements of MS Office, but it is not an adequate replacement for Excel) Most serious CFD practitioners that I know run a mixture of Windows and Linux machines.

However, when you actually measure the difference in performance, it mostly comes down to the particular compiler, not operating system. Code compiled with gcc, for example, is slower than code compiled with Intel or Pathscale. In fact, I have tested code compiled with gcc, and the executions speed was the same under Windows, Linux or Wine under Linux! So it didn't care about the O/S, it only knew about the low-level instructions and the hardware.

Re: OpenFOAM vs. Fluent & CFX
 

"However, when you actually measure the difference in performance, it mostly comes down to the particular compiler, not operating system. Code compiled with gcc, for example, is slower than code compiled with Intel or Pathscale. In fact, I have tested code compiled with gcc, and the executions speed was the same under Windows, Linux or Wine under Linux! So it didn't care about the O/S, it only knew about the low-level instructions and the hardware."

I suspect the computer was not been used for anything else during the test - so the OS did not have to interfere with the running of the code. If for example the job was running in the background while you were doing something else such as editing text in openoffice would this still be the case?

Some points you missed off of your list include stability (linux rarely needs rebooting) and the fact that it has had support for multiple cores longer than windows.

Re: OpenFOAM vs. Fluent & CFX
 

Tom,

i'm not biased to win or linux, currently i use dual-boot system.

question to your answer: linux is used almost in cluster technology becasue until 2003, windows does not support needed message passing like MPI, but after 2003, server version of windows is appeared and to my knowledge (related to 2006) it successfuly manages more than 256 nodes with comparable performance andscalability. Today when i enquiry aboyt its, i read something about 1000-10000 nodes!

So in future it be possible to compare.

Another critical issue (i select linux just for this reason), windows does not support diskless cluster, i.e., each node should has a hard-disk and a distict registered windows (expensive: hardware/software, important for large cluster).

In my experience with both system, i could not say what is better, because contrast between performances is not sensible (i did not do a profiling sofar).

Finally word: usually scientific community reject windows by default (is somehow emulation), but if we see current sitution, you see that windows is very common and public, e.g., read 2007 static report of CFD-Online Forum which show windows be dominant OS !

Re: OpenFOAM vs. Fluent & CFX
 

"I suspect the computer was not been used for anything else during the test - so the OS did not have to interfere with the running of the code. If for example the job was running in the background while you were doing something else such as editing text in openoffice would this still be the case?"

Pretty much. CFD uses so much more of the CPU than anything else that normal "office" tasks have very little influence. Sure, if you are doing some interactive things that require a lot of CPU (like CAD modeling), you will notice the effect on the CFD performance. But this is determined by the relative priority that you assign the two tasks, something which is equally easily done under Windows and Linux.

"Some points you missed off of your list include stability (linux rarely needs rebooting) and the fact that it has had support for multiple cores longer than windows."

XP Professional is pretty stable, you know. It doesn't need many reboots either. In a way I'm playing devil's advocate here. I too prefer Linux for a lot of my work, but the fact is that it doesn't hold a huge advantage at the moment. Where Linux has generally had a big advantage is during periods of transition of the hardware. When hardware moved to 32-bit, Linux was a initially a far better multi-tasking O/S, and it was only NT and finally Windows 2000 that made Windows competitive again. Similarly, when the 64-bit move came, once again Linux64 was almost immediately a viable option, but it took a surprisingly long time for 64-bit Windows to become a viable alternative. Even now, there are devices and software that aren't compatible with XP64. Anyway, this has gone rather a long way off topic, except perhaps to point out that open-source evangelists need to keep an eye on reality as well!

Re: OpenFOAM vs. Fluent & CFX
 

Charies, fine idea, it is indeed correct.

e.g. gcc could be run under cygwin or mingw in windows which is slowdown due to this (i compare with MSVC 6. and show 40 % slow down for my application).

so if anyone compare a compiled code by GCC in windows and linux, his comparison is not fair !

Re: OpenFOAM vs. Fluent & CFX
 

So mean of you walter! You also started work or research (or whatever you do) as a graduate student. Didnt you?

Thank you for your reply chen.

Marco

Re: OpenFOAM vs. Fluent & CFX
 

"question to your answer: linux is used almost in cluster technology becasue until 2003, windows does not support needed message passing like MPI, but after 2003, server version of windows is appeared and to my knowledge (related to 2006) it successfuly manages more than 256 nodes with comparable performance andscalability. Today when i enquiry aboyt its, i read something about 1000-10000 nodes!"

As far as I am aware none of the major "supercomputer" manufactures use windows and so I suspect that the "1000-10000 nodes" comment has nothing to do with a full scale MPP fluids simulation.

Everyone knows, rightly or wrongly, that windows is the dominant OS for business and home use. It's not so clear for scientific computing - Sun, HP, Cray, NEC, IBM, ... all tend to use a version on Unix in their systems.

Re: OpenFOAM vs. Fluent & CFX
 

> I suspect that the "1000-10000 nodes" comment has nothing to do with a full scale MPP fluids simulation.

I did not use myself and as i said i only read about. look at this link (1024 node is claimed to me commersialized):

http://h18004.www1.hp.com/products/q.../12574_na.html

this presentation gives interesting results:

http://www.winhpc.org/dl/presentatio...rd_HP_WCCS.ppt

comparison between Linux/windows cluster, it showed that difference is -+ 10 % (somethimes win is supperior and sometimes linux !),

particularly it has some results for runnig Fluent on both system, which could be interesting to this Forum's member (in this case Linux is 5-10 % better), note that it is not sign for superiority of Linux becasue all thing are not same (at least programming of Fluent and its used compiler for each OS)

PS: I priori know that some peoples with closed eyes still say Linux Linux ... but we do not say any becasue fair comparison is not simple

Re: OpenFOAM vs. Fluent & CFX
 

One thing is a benchmark and something completely different is the daily use such a configuration :)

Re: OpenFOAM vs. Fluent & CFX
 

Ok bottom line is OpenFOAM is better. Thank you all for participating in the discussion.

Marco

Re: OpenFOAM vs. Fluent & CFX
 

Who said that? This is what your original post asserted. There were various arguments either way..now you "close the discussion by repeating your statement". I give you an F in debate.

These arguments are always very silly and never get anywhere.

The real "bottom line" is that each is a tool. In the correct hands each tool can be made to do some nice work. Similarly in the wrong hands you can just as easily produce cra* answers with any of the codes.

Re: OpenFOAM vs. Fluent & CFX
 

The real bottom line is you have difficulty in understanding English. It has been clearly written by many posters that OpenFoam is nowhere near to commercial solvers in terms of features etc. It is good program but still got to be developed a lot.

You can live with your bottom and line though. No probs.

Re: OpenFOAM vs. Fluent & CFX
 

Apart from air and possibly water, what free thing is better than it's commercial alternative? OK, OK, apart from price...

One of the advantages of a capitalistic culture is that if it's good someone will want to make money out of it and will do so if people want to buy it. Personally I like to pay for things, a certain amount of responsibility is then vested with the seller to honour the price they are charging. Without this albeit profit driven relationship, one has to rely on trust and integrity. Honourable goals indeed but ones that tend to be corrupted by our rather Darwinistic approach to commerce.

Maybe I missed it in this thread but how does OpenFOAM Ltd. survive? Is it beggarware? Does it rely on advertising? Does it make it via consultancy services? I'd trust it more if I knew that, like the rest of us, it was trying to make an (honest) crust!

opaque and the like ...
 

The very fact that "opaque" does get so upset about the post shows that Ansys and others are not taking developments like OpenFOAM lightly ...

I have been personally involved in a comparison between OpenFOAM and CFD-ACE+ for sloshing simulations ... yes, OpenFOAM does not have a shiny GUI and might even be akward to use sometimes, but in terms of performance and accuracy it had an edge over the commercial code. Admittedly that was just one commercial code, and a minor one as our dear Ansys disciple pointed out.

Re: OpenFOAM vs. Fluent & CFX
 

...having said that I suppose open source software development could herald fundamental changes to the way software commerce works. A developer I work with has pointed out that Qt (amongst others) has a model whereby they offer two versions, an open version and one for commercial distribution. The latter making money, the former widely adopted, used and more importantly tested. Loads of web based product provisions are advertising funded. One thing is for sure, one can not assume that the standard annual lease or perpetual+X% maintenance model common in the commercial CFD market will survive intact indefinitely. Is this the start of the end or the start of the beginning?