State of the art in CFD technology
 

Dear all

I'am starting my PhD research which the subject is the simulation, whit a CFD code (Fluent), of the control sewer overflow structures (sructures into the sewer networks). So, I would know the state of the art of the CFD technology.

Regards

Re: State of the art in CFD technology
 

(1). We don't know what is exactly inside a commercial code. So, there is no way of telling the state of the art of a CFD code. (2). The CFD technology itself covers many different fields, such as, the geometry modeling, the mesh generation, the numerical formulations (finite-difference, finite-volume, finite-element,...), the solution procedures, the turbulence modeling, the graphic post processing. (3). There are many technical journals available in these fields. So, you should be able to find additional information in the library. (4). I would strongly suggest that you first define your problem, then try to derive the equations, and see whether you can understand it and solve your problem. (5). Using a commercial code takes only a few weeks to learn, and a few months to get a solution (assuming that it is a difficult one). A PhD is not required to run a commercial code.

Re: State of the art in CFD technology
 

You are dreaming too much to get a PhD. using commercial codes. Commercial codes have limited applications. Small schools for example like University of Nebraska or say University of Alabama may give you PhD. if you use commercial softwares. There are lot of PhD. degrees you can buy with money where you don't have to do any creative work. I agree with John, "We don't know what is exactly inside a commercial code. So, there is no way of telling the state of the art of a CFD code."

Re: State of the art in CFD technology
 

I don't think the gentlemen at the universities of Nebraska or Alabama would like you to characterise their institutions as 'small', actually these schools are large in size and in reputation

Re: State of the art in CFD technology
 

Usually graduate schools ranked in top 50 or top 60 are considered big schools (in USA) with good reputations. I just mentioned some schools name for showing some example, nothing more than that.

Re: State of the art in CFD technology
 

That's ridiculous! If you are a Civil engineering student studying sewer overflow structures, using anything other than a commerical code would be irresponsible. It's one thing if you are studying CFD for your thesis, but this fellow is *using* CFD.

No university would insist that he actually roll his own code, and any reputable CFD software vendor will completely describe the methods used in their code (which are almost always well-known from the research literature anyway). The value in commercial codes isn't coming from in-house secret developments as much as the total integration of many capabilities. So I don't see the 'black box' theory as a real issue. And to say that commercial codes are more specialized than research codes??? What are you smoking?

going on...I am aware that the ThermoFluids department at Stanford (is that reputable enough for you?) has PhD students using commercial codes for 2 purposes: (1) in support of their experimental work, and (2) using the "user-defined subroutines" extensions to develop a new model or something like that without having to write an entire code. To get to the state-of-the-art in CFD nowadays, you can't possibly write your own code unless you are going to stick with simple geometry.

In my opinion, if you ask enough CFD people, you'll very quickly get the picture that the days of rolling your own CFD code as a PhD project are very much long gone, and there never were such days for Civil engineering students.

Re: State of the art in CFD technology
 

1). We don't know what is exactly inside a commercial code. So, there is no way of telling the state of the art of a CFD code. (2). The CFD technology itself covers many different fields, such as, the geometry modeling, the mesh generation, the numerical formulations (finite-difference, finite-volume, finite-element,...), the solution procedures, the turbulence modeling, the graphic post processing. (3). There are many technical journals available in these fields. So, you should be able to find additional information in the library. (4). I would strongly suggest that you first define your problem, then try to derive the equations, and see whether you can understand it and solve your problem. (5). Using a commercial code takes only a few weeks to learn, and a few months to get a solution (assuming that it is a difficult one). A PhD is not required to run a commercial code.

What's problem?
 

I think so for you CFD is only set of tools for example as a set of pencils. But can you say more about your engineering problem?

Re: State of the art in CFD technology
 

And to say that commercial codes are more specialized than research codes??? What are you smoking?

Sorry, I don't smoke.

Re: What's problem?
 

J'espère que vous pourriez lire ce message.

Je suis ingenieur civil et je connais tres bien mos sujet de thèse. A chaque fois que lis vos messages vous ne m'apportent rien. Il y a des gens comme Monsieur Chien qui m'ont aidé a mieux comprendre ce qui est l'etat de l'art de la tecnology CFD. Donc, merci quand même.

Vous devriez savoir que ce moyen de communication ce n'est pas pour insulter les autres et pour ceux qui me demandent qu'est ce que je fumme je vous repond: RIEN.

En tout cas pour le Monsieur qui me dit que son Université est trés reconnu (Stanford je crois), je lui dit que la technology CFD que je vais utiliser est pour valider un autre simulation dans un logiciel hydrodynamique de simulation de reseaux d'assainissement.

Je crois que vous drevriez savoir aussi que les structures de déversement (Deversoir d'orage en Francais et CSO en anglais) ont un rôle primordial dans la recherche en hydrologie urbaine. Donc, je crois que je me suis trompé de groupe de discusion car ici j'ai l'impression que existen seulement de savants mais en CFD seulement.

Merci a tous vous, mais vous ne m'apportent rien, sauf Monsieur Chien.

Re: State of the art in CFD technology
 

I think that you could know this message posted octobre 8, 1999.

My name is Juan Carlos. I am a civil engineer from National Autonomous University of Mexico (UNAM). In the Civil Department of the National Appliend Sciences Institute of Lyon (INSA-Lyon), France I was study a posgraduate course in which I developed like finaly work the research "Descrption and modelling of CSO models (frontal and lateral) into an HD (hydrodynamic sewer system software)". Now I am starting my PhD research at Civil Engineering Research Unit-Urban Hydrology at INSA-Lyon and where the principal subject is a construction, analysis and validation of hydraulics models of CSO into an HD software. This procedure will be calibrated and verified with a CFD softwere in order to establish the practical means for CSO's HD modelling.

Juan Carlos GARCIA-SALAS

Re: State of the art in CFD technology
 

Hi

I would definitely disagree with your statement concerning creative work and the use of a commercial CFD-code. I have spent a number of year investigating cooling tower performance experimentally. Currently I am using a commercial CFD-code to determine whether the major trends that I observed experimentally can be duplicated numerically and the results thus far have been very positive. The flexibility provided by numerical simulation has opened new avenues of thinking and a lot of creativity has gone into forging these avenues. I do not advocate the use of commercial CFD codes to do fundamnetal research prior to the necessary validating of numerical data against experimental results, but if you can show that the numerical results compare favourably with experimental data the commercial CFD-code becomes a powerful research tool.

I would agree that if your goal is to make a fundamnetal contribution to the CFD field then producing your own code is essential. From what I understand of Juan's message it would seem that he is not that interested in making a fundamnetal contribution to the field of CFD, but rather he hopes to use CFD as a tool in his research. I do not see how his PhD would be "bought" if he can show that his numerical results compare favourably with experimental data.

regards

Chris

Re: State of the art in CFD technology
 

Daer Mr. Chris

This is exactly, I am not interesed to make a contribution in the field of CFD research. I only hoped to know this technology because my PhD research requires, for validating and calibrating the CSO models into an HD sewer system software, the technology CFD and the experimental data from special structures into sewer networks, nobably in Lyon France.. and I say: My PhD research is in the field of URBAN DRAINAGE.

Cordially

Juan Carlos

Re: State of the art in CFD technology
 

Hi

My advice to you is to be very rigerous in validating your numerical results. It is very easy to end up in the situation where you don't know whether you are observing a physical phenomena or just some numerical anomaly. I have spent the better part of two years on the development and testing of my models before I started looking at the real topic of my PhD. What some of the other people have said is very true: you don't know what is inside the commercial codes so proceed very carefully and make sure you understand what you are doing. I spent a lot of time reading up on discretization schemes, turbulence models etc. I also tested there influence on my results. Commercial codes are deceptively easy to use and the results always look very pretty!!! But that says very little.

I wish you well for the task ahead!

Regards

Chris

Re: State of the art in CFD technology
 

(1). I like your comments. I think this is the right place to address the proper use of a commercial code. (2). Number one, you have spent a number of years investigating the problem experimentally. This is the key requirement. I am assuming that you understand your problem completely. (3). At this point, you are sure that your experimental investagation is reliable. (4). Number two, you are using the commercial code to check whether the numerically predicted major trend is consistent with the experimental results. So, basically, you are doing code validation. You don't trust the commercial code, you trust the experimental data. (5). From your comments, so far you are pleased with the commercial code results. And that is a good new for you. (6). At this point, you then make a positive comment on using a commercial code as a tool. (7). The fact is to reach this conclusion, you need to spend a number of years investigating your problem experimentally, and then validate the code against the test results. (8). I think, that is the right approach. But it will add a number of years to the PhD program doing experimental investigation first. (9). In turbomachinery, even the experimental results are not reliable in our case, not to mention the convergence of the commercial codes. (10). I like the idea that: a PhD student using a commercial code must demonstrate that he can obtain reliable experimental results first. This will demonstrate his real understanding of his problem. Once this is done, he can try to validate the commercial code against his test results. (11). Although this is a practical approach. it tends to make the person using the commercial code looks like a "second-class citizen". (12). I would hope that some days we can just go ahead and use the commercial code, without spending a number of years doing the testing first. This is probably the state of the art of CFD. (if we make the vendors of the code responsible for every bad results obtained by the users, then that goal should be realized earlier. The current picture is: my code is good, but don't tell me you are getting bad results, I have said clearly in the fine print that I am not responsible for your bad results, but I still say that my code is a good code. So, the only way a user can protect himself is to learn how to write his own code. There is no other alternatives. The PhD problem is an unknown, and if the commercial code is also an unknown, unknown + unknown is not = real answer. Unless, you have just redefined the + operator in a different way.) (13). To repeat my suggestion here: a commercial code is best suited for a person who knows how to write a code to solve his problem, or a person who is willing to spend a number of years doing experimental investigation first,followed by careful validation of the code against his results. Anyone else using the code is not protected against the bad results.

Re: State of the art in CFD technology
 

Your main work seems like experimental work in fluid dynamics which requires lot of expermentation. Comparing your results with numerical simulations to validate results seems auxiliary work. Probably you will survive but remember that "What some of the other people have said is very true: you don't know what is inside the commercial codes so proceed very carefully and make sure you understand what you are doing."

And I also wish you best of luck.

Re: State of the art in CFD technology
 

Can someone explain to me what they mean by the phrase 'CFD is a black box'. From my point of view, CFD can be a black box if one is a Fluid dynamist and knows very little about numerical analysis. It could also be a black box to some numerical analyst who knows very little fluid dynamics. This point is well put in the preface section of Ferziger's CFD text. He said that you have to be both a numerical analyst and a fluid dynamist to be a good CFD analyst. If one has this ideal background I do not see any reason why one cannot pick up a Fluent or CFX manual and get a very succint picture of what is happening in ones area of interes in these codes. Put differently, these codes are not black boxes, if I understand the term. They may have some constants that they use that they do not want someone else to know about but that does not make the code a black box. They may have some errors but so do the programs we write. Errors should not make them black boxes. As responsible users of CFD, we should tell other users that commercial CFD packages are easy to use but very difficult to use properly. Note the word properly.

We should be thankful to the academic community whose R&D efforts have helped CFD develop into a useful design tool. We should also be thankful to the 'commercial packages' for implement these good ideas. During the implementation of these ideas mistakes are made, we should help out by pointing out the mistakes to the developers, so they can be corrected. This way we help improve the code. Several years ago, I used to write code to solve specific problems. I almost always finished writing the code after the project was over. The reason being that it is difficult to debug and test a piece of code properly. Now, I let better programmers do the programming and I do my careful analysis. I hope I have not offended any one because that is not my goal.

Re: State of the art in CFD technology
 

Can someone explain to me what they mean by the phrase 'CFD is a black box'. From my point of view, CFD can be a black box if one is a Fluid dynamist and knows very little about numerical analysis. It could also be a black box to some numerical analyst who knows very little fluid dynamics. This point is well put in the preface section of Ferziger's CFD text. He said that you have to be both a numerical analyst and a fluid dynamist to be a good CFD analyst. If one has this ideal background I do not see any reason why one cannot pick up a Fluent or CFX manual and get a very succint picture of what is happening in ones area of interes in these codes. Put differently, these codes are not black boxes, if I understand the term. They may have some constants that they use that they do not want someone else to know about but that does not make the code a black box. They may have some errors but so do the programs we write. Errors should not make them black boxes. As responsible users of CFD, we should tell other users that commercial CFD packages are easy to use but very difficult to use properly. Note the word properly.

We should be thankful to the academic community whose R&D efforts have helped CFD develop into a useful design tool. We should also be thankful to the 'commercial packages' for implement these good ideas. During the implementation of these ideas mistakes are made, we should help out by pointing out the mistakes to the developers, so they can be corrected. This way we help improve the code. Several years ago, I used to write code to solve specific problems. I almost always finished writing the code after the project was over. The reason being that it is difficult to debug and test a piece of code properly. Now, I let better programmers do the programming and I do my careful analysis. I hope I have not offended any one because that is not my goal.

Re: What's problem?
 

What language is this? It is certainly not english.

Re: State of the art in CFD technology
 

in my opinion, even if you can write your own code, you still have to spend enough time to do your experiment to validate your own CFD code. it's like you cooking coffee, the CFD is the sugar you add into your cup. anyway you must have a cup of coffee first, And, not all people like sweet coffee. maybe Juan's superviser like,

Re: What's problem?
 

Mr. Ziaul

Exactly, you have the bingoThis language is the french. The Victor Hugo's, the Balsac's, the Curie's, the Ampere's Language. Did you know this names?

Juan Carlos

Re: State of the art in CFD technology
 

Hi

Fortunately the 3 years of experimental testing had resulted in a Masters degree with the PhD covering the numerical work. I do however agree that if you start a PhD with no experimental work in hand you cannot seriously consider using a commercial code. And even if you write your own code it by no means ensures you of good results, there are numerical and modeling aspects that even good codes struggle with, turbulence is but one example.

I must also admit that my personel belief is that if you are serious about CFD then writing your own code is essential. At some stage you must aquire a fundamental understanding of how the whole thing is put together. In fact I have resolved myself to writing my own code in my spare time although the going is slow due to time constraints. It seems to be rather difficult to get postdoc positions that allows one to do this type of thing for a "living". I'll keep looking anyway!!!

It also seems that more and more academic institutions are moving away from the more fundamental CFD development to using commercial codes to solve or investigate problems for industry. This is especially true for institutions that are only now venturing into the field of CFD. Very few companies are willing to give money for code development that some time in the future might yield some rewards, it is easier to get money for a problem that can be "solved" now with a commercial code. Although I have respect for the circumstances that "enforce" this way of thinking I do not necessarily agree with it.

I think I have said quite enough already, I hope this was not to tedious for all involved!

Regards

Chris

Re: State of the art in CFD technology
 

.

Re: State of the art in CFD technology
 

Hi

I have a little vocabulary problem

comercial CFD package = comercial CFD code

Regards

Re: State of the art in CFD technology
 

Mr Salas, i think you have not gotten the answers to the questions you asked. if i'm not mistaken you'd like to know the algorithms,characteristics, and properties etc of the Fluent code you'll be using to model a problem you know experimentally.

to answer this question i think you should contact the company that makes Fluent. they are online at www.fluent.com (if i'm not mistaken). also you may have distributors and/or branches of the company in France so you can speak to someone over the phone or correspond with in some other way. they should be able to provide you with references written by company members and documentation describing some of the workings of the code. they should also be able to provide you with the assumptions, strengths, and weaknesses inherent in the code and tips to improve your accuracy and performance.

i think the use of a commercial codes like fluent would definitely be appropriate in this case because i think it is suited to your problem. but i think you should maintain contact with someone at the company who can assist you.

you must remember that some of the people on this group have a different background from yourself and so may not understand your problem or may have preconceived ideas. good luck with your work

Re: State of the art in CFD technology
 

Hi Gentlemans

Thank you for your advices. I know that some of the people on this group have a differnet backgroud..this is normal. At this moment I am very happy because I'am understandig (a little only) what is the technology CFD and the applications into engineering problems.

Regards from Lyon France

Re: What's problem?
 

This time I am really lost! I don't know french.

Re: State of the art in CFD technology
 

I can't agree with you more.

Re: State of the art in CFD technology
 

Different people may have different ideas and opinions. Yet I want to point out that, interestingly enough, many state-of-the-art technologies in CFD these days are geared toward bringing CFD tools (not necessarily commercial for commercial CFD code averse folks) to the hands of designers and engineers who may have some fluid mechanics background but not necessarily experts in CFD, i.e., toward making CFD tools easy-to-use, efficient and affordable.

And considering that you're based in France, I must mention that Fluent France has a highly competent and knowledgeable group of CFD engineers who can help you get up to speed with using FLUENT software. And Fluent France holds every year their Fluent Users Group Meeting (we call UGM in short). I strongly recommend you attend the UGM next year unless you plan to graduate this year. Last September this year, they had about 150 client attendance, and lots of excellent user papers were presented by users like you, whose major expertises are not necessarily in "writing CFD code", but something else like design, trouble-shooting, experimentalists, etc. So take heart !

Among all the replies to your original query, I like the ones from Amadou Sowe and Clifford Bradford, which will help you develop a positive and objective attitude toward CFD.

Re: State of the art in CFD technology
 

(1). It is really very hard to understand your message. (2). The need to use CFD comes from the need to solve fluid dynamics problems. These can be problems to reduce the auto emission level to reduce the health harzard, problems to design turbine blade to reduce fuel consumption and improve engine life, problems to design fighter aircraft to improve performance, problems to reduce the pollution from a combustor or a furnace to clean up the air, problems to design a clean room for IC manufacturing plant for productivity, ....etc... (3). These fluid dynamics problems occur at the design stage, the production stage, and the service stage. So, it is linked to the product from the begining to the end. (4). It becomes clear that the ability to provide accurate and reliable answers to these fluid dynamics problems is the most important issue. (5). So, as an engineer working in this field, the most important issue is to know whether the solutions obtained are accurate and reliable. (6). To achieve this goal, researchers have been working on various numerical methods to provide more accurate results (assuming that the converged solution is achievable), different turbulence models to provide more realistic representation of the turbulent flows, etc... (7). So, there are numerous methods and models around, which were developed under different conditions and for different problems in mind. When some of those were implemented in a package ( a collection of libraries, modules, subroutines and programs), and sold on the market under "as is" condition, it is highly questionable that a user (without proper pre-caution and a systematic approach) can easily obtain the desirable accurate and reliable results in a so-called user-friendly program environment. (8). All of the questions and answers presented here were trying to make sure that the solution obtained is indeed the desirable accurate and reliable solution. (9). So, if the vendor of the commercial code is willing to say that the solution obtained by a user is always accurate and reliable, then, both the vendor of the code and the user of the code would be very happy. But, so far this approach is not practical, and no vendor is taking this approach. (10). So, Ask yourself, would you want to buy a car under "as is" condition? Would you want to buy a car which was designed by a commercial code under "as is" condition? And, next time, when you travel by air, would you want to fly in an airplane which was designed by a commercial code under "as is" condition? (11). If your fluid dynamics problems are not in these areas, then perhaps, the use of CFD or commercial CFD codes is not essential at all. I mean, if your problem is happy with a 1-D code, then most questions and answers related to the 3-D problems presented here are just like Saturday night music.

Re: State of the art in CFD technology
 

Hi John,

I agree with Amadou's assessment above, and I'll give you my take. With your car analogy, you're asking if someone wants to buy a car "as is", with no "warranty" or guarantee of accurate results. Well, if I need transportation, and my only two options are buying a car "as is" or building it myself, I'll take the former. Likewise, most people don't have the time to write their own codes, and probably are not expert enough programmers to do a better job than the team of professionals who work as commercial code developers.

However, as Amadou points out, one should have a strong enough background in both fluid dynamics and numerical methods to be able to understand exactly what is being done inside the code. Even an expert mechanic would be more efficient to buy the "as is" car than build it himself. He has the advantage of being able to recognize the potential problems. And it is important to note that this expertise does not automatically come from code-writing. I have written my own codes, mostly to gain an appreciation of what it takes. And it usually comes down to wrestling with exactly how to implement a certain scheme (that I didn't develop) and models (that I also didn't develop) and get them to work properly. Implementing a k-e model in your own code by no means makes you aware of exactly what problems are going to show up in what flow situations.

Finally, one more analogy. If I was an experimentalist, and had spent a decade of my life building a complicated measurement apparatus, I'd be pretty proud of it. And then if my colleague next door went out and bought the same thing, I'd probably try to convince people that really, if you don't build it yourself, then you probably aren't going to get useful results. It's baloney, of course, but I'd have an interest to protect. My colleague's ability to get useful results would have to do with his knowledge and experience, not on whether or not he completely pieced the thing together himself.

Should one be competent and well-versed in fluid dynamics and numerical methods to use CFD properly? Absolutely. Should one have to write his own code? Of course not.

Regards, Keith

Re: State of the art in CFD technology
 

I am very sorry that you found it hard to understand my message. You are very scornful of the CFD codes because they sell their software 'as is'. If I am not mistaken every software company usually has this disclaimer in their license agreements. I do not think that this is unique to the CFD software companies alone.

I will try to clarify my point by answering your questions about buying products 'as is'. It is very funny that you ask whether I will buy a car as is; infact I just bought a 1988 Buick as is. Inorder to buy a product 'as is ' you have to do one of two things:

(1) Make sure that you understand the product well enough so you can judge whether the product will do the task you want to buy it for.

(2)On the other hand if you cannot do (1) for yourself hire some one qualified to do it for you.

I am a mathematician by training who does not know much about cars so I had a good mechanic check the car for me. The only problem he found was a torn CV joint cover. I bought the car and had a new boot put on.

The point I was trying to make was that some of us do not have the required background to make an objective condemnation of the CFD software industry. The required background has to include the key components of CFD( numerical analysis and fluid dynamics). Some of our community members seem to be strong in one or the other but not both.

Another point you made was whether I will fly on a plane whose designers use commercial code under 'as is ' condition. I am sure the designers of the commercial planes use software that has a disclaimer somewhere in their license agreement. This disclaimer precisely declares the 'as is' condition. By the way I hate flying because I am not in control of the plane. Let me get your feed back.

Re: State of the art in CFD technology
 

Well put, Keith.

Re: State of the art in CFD technology
 

(1). You are absolutely right. "One should not have to write his own code." The same is true: " One should not have to build his own car." (2). I agree with you that "when there is no choice, one would probably use whatever available to him". (3). The fact is : many leading companies in industries are not spending research money on their CFD activities, they are trying to save engineering salary by puting commercial codes on their computer system. (4). Back to your comments : "one should have a strong enough background in both fluid dynamics and numerical methods to be able to understand exactly what is being done inside the code." This can be done only if " the source code listing is available". (5). Very few companies are willing to give you the source code listings. And this is exactly why the commercial codes are labeled as "black box". (6). The need to know how to write his own code is to have knowledge to protect himself when using a commercial code. The same is true that you can buy a car "as is", but you are likely to get it checked out by a car mechanics first. The car mechanics is just like a person with knowledge to write his own CFD code. He can check out a car without actually take the whole car apart. (7). Are you sure that the team members works on the commercial code development are "real professional"? (8). As a matter of fact, in most cases, you don't know their names, their background training, their experience, their knowledge in solving your problems, not to mention the code itself. (it is fairly common that an error identified by the user is not fixed for a long time, because the person who had worked on that portion of the program is no longer with the company. And if that part of the program was written by a subcontractor company, there is not much you can do or he can do to fix it. )

Re: State of the art in CFD technology
 

(1). I think we have the same view point. (2). We both agree that a car "as is" will always have some problem. (3). So, it is the approach taken to eliminate the problem. (4). When you take the car to the professional mechanics, you are taking the professional approach to solve the problem. This is because the mechanics works for you. It makes no difference whether you have the knowledge about the car or not. As long as you two can find the problem and fix it. It is the approach which is important. (5). So, I agree with you that there is no need for you to take the auto mechanics class at the nearby community college in the weekend, in order to buy a used car. (6). By the way, I used to have a Buik convertable, a Buik Skylark, a Buik Century. But recently, I am driving a small Honda. The difference is I used to visit the garage often to get my Buiks fixed, even when they are brand new. Now, with Honda, I can start the car with only one turn of the ignition switch, and I don't have to visit the garage to fix the car any more. (7). I must say that, the purpose of the discussions is to bring out the nature (of the state of the art ) of the CFD technology (commercial codes represent part of the technology). Through the awareness of it, some professional approaches on the users side could be developed to better utilize the CFD technology. (there is nothing personal in the discussion , it is always aimed at the rest of the readers.)

Re: State of the art in CFD technology
 

Hi

I want to make two points:

1) When you get into a plane (even a car) you know that it had to pass some set of standards set by some government agency. It does not mean that nothing will go wrong, but it means that great care has been taken to make the plane safe. To some that may be a comfort, to others not. I don't know of any agency that checks up on commercial CFD-codes. The "checking" is left to the user and the user has so little time......

2) A year or two ago I was injured participating in a organized game. While rushing me to hospital the person in charge was thoughful enough to remind me that I signed a form that proclaimed that the game was played at "own risk". At that stage I had other things to worry about. It was only much later that a lawyer friend of mine told me that even if I had signed their disclaimer it did not mean the company hosting the game was not liable. The very fact that they provided protective clothing for the game made them liable since they obviously knew that without proper protection injury was very likely. The important phrase is "proper protection". They provided protection, but was it enough? Are the companies selling CFD-codes doing enough to protect the unsuspecting users?

Finally, and this is not a third point, I use a commercial CFD-code for research purposes. It has taken me some years to feel "comfortable" with the numerical results. A lot of my time was taken up by testing various aspects of the code by comparing the results to experimental data. I could have saved a lot of time if there had been some organization of repute that had done the validating of the code and had given it a seal of approval. Maybe this is an impossible situation to have such an organization, but it would be very nice wouldn't it?

Regards

Chris

Re: State of the art in CFD technology
 

(1). I would say that you have just identified a great business opportunity, that is, a CFD testing laboratory to test and validate the commercial CFD codes. (2). In this way, at least, a commercial CFD code will have to meet some standard requirements before it can be placed in market for sale.

Re: State of the art in CFD technology
 

Is this what the WUA-CFD (World User Association in Applied Fluid Dynamics http://www.wua-cfd.com/wua-cfd/) are aiming for?

I don't know much about them but I stumbled accross their web pages the other day.

Regards

Althea

Re: State of the art in CFD technology
 

comment to point (1)........

You do not know of any agency that checks up on CFD may be true. Infact I do not know of any agency that checks up on any software including our operating systems. May be I am wrong but I will be glad to get some examples from some one out there. You are right when you said that the user is the one doing the checking. This is the main reason why I kept saying that to use CFD correctly you have to know both numerical analysis and fluid mechanics very well.

comment (2).........

To me, I do not think there should be any 'unsuspecting users' of CFD. It is too complicated a field to not suspect your every move. It is a lot more comforting to be 'suspecting' in a familiar environment than in one you are less familiar with.

Re: State of the art in CFD technology
 

(1). Based on reports, system software companies such as Microsoft, and computer games companies do test their software in-house and by outside professional programmers. (2). They also have a large number of in-house software testers. (3). They can't afford not to have their software thoroughly tested before release.