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September 29, 1998, 20:14 
How large is the 2D CFD market?

#1 
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Hi,
There have recently been a few interesting exchanges on the list regrarding CFD market size and its potential growth. I am curious as to how much of the market is 2D related. Is there commercial interest in solving 2D problems, especially if one can do a successful 2D DNS (no turbulence modeling) of complex geometries for Reynolds numbers of say up to 50,000 (which is already too high considering that 3D effects kick in much earlier)? Thanks in advance for your comments Adrin Gharakhani 

September 30, 1998, 09:43 
Re: How large is the 2D CFD market?

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From the user's point of view (the user of a commerical code), he is interested in solving the real world problem. The assumption behind using a commerical code is to save time ( the time required to develop his own code). Unfortunately, the real world problem is highly 3D. Even with a commerical code, it can be very time consuming to build the 3D model and to obtain the 3D solution. (sometimes, it takes several weeks on workstation for a run ). Sometimes, you are limited by the computer memory ( a workstation with one giga RAM is needed for 3D unstructured mesh problem using a commercial code ). With these two limitations ( time and memory), users frequently are forced to solve 2D problem ( model problem ). I would say, most real world 3D problems are still unsolved because of computer speed and memory. The design procedure being used today is still: 1D analysis, 2D analysis and 3D analysis. 2D analysis is still part of the design process. The actual need for commercial code is in the area of 3D complex geometry flow problem, where the need is not high enough to justify the inhouse code development. The design code, 2D or 3D, normally are generated inhouse or highly modified inhouse. So, the 3D world or the market is still wide open. ( because researchers are still trying to solve 2D problems ). In short, users need 3D solutions, but they are forced to solve 2D model problem because of computer speed and memory limitations. The market is still 3D. There is no 2D airplanes, cars, and ships.


September 30, 1998, 11:04 
Re: How large is the 2D CFD market?

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>Even with a commerical code, it can be very time consuming to build the 3D model and to obtain the 3D solution. (sometimes, it takes several weeks on workstation for a run ). Sometimes, you are limited by the computer memory ( a workstation with one giga RAM is needed for 3D unstructured mesh problem using a commercial code ).
Well that depends.... If you want engineering answers on industrial timescales (where time to market is counted in weeks and design optimisation in days) then there are commercial CFD codes (sorry, codes that employ CFD) that fulfil that role. I have modelled large telecommunication rack systems with a structured cartesian grid using 100,000s of cells that take a day to build, an hour to grid and I have my convergged solution ready for me when I come in the next day. I can guage wether the current design is thermally efficient and if not can investigate a number of design variations within a week. This form of CFD analysis comprises the other % noted by Ferit. 

September 30, 1998, 12:01 
Re: How large is the 2D CFD market?

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Maybe people are heading in the wrong direction of using unstructured mesh ( which requires large computer memory ), or maybe we simply don't know what we are doing. I am sure that structured Cartesian mesh requires less memory, less computing effort. But the capability to handle the complex geometry is not as good as unstructured mesh approach. You have just pointed out a very important direction : " Quick 3D answer with useful results " , that is 3D PC games approach ( vs 3D movie quality prerendered animation, which is slow ). This is probably a more attractive market, that is a fast 3D code which will provide 1st order useful solution for engineering application. Just like the computer animation field, you have gamequality ( 3D real time) vs moviequality ( 3D raytracing ). Thank you for your information. This market maybe more profitable. As a matter of fact, you really don't need the exact 3D answer. What you need is something to guide you to a better design. This will definitely change the balance of the CFD market place. ( the need of user for a quick and useful 3D CFD answer ). Thank you again for your information.


September 30, 1998, 13:00 
Re: How large is the 2D CFD market?

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To answer Adrin's Q: A lot of CFD work in the realworld marketplace is 2D. By "a lot", I mean about 5060% and this number will depend upon which subfield of mech/chem/materials engrg you are talking about. The reason is that even though the problems may be 3D, quite a bit of qualitative information can be obtained from 2D analysis, and in fact is routinely obtained. A number of times, with a few simplifications to the geometry, 3D cases can be solved with the 2D axisymmetric assumption. The auto industry I'm familiar w/ certainly is an example.


September 30, 1998, 14:44 
Re: How large is the 2D CFD market?

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Thanks for an interesting exchange! I have no doubt that the real world is 3D (actually it is 4D, I never liked "steady state" solutions  alot of significant information is lost by this assumption, but I digress).
The reason I asked about the 2D market is precisely because 3D codes for complex geometries (unstructured mesh) are practically out of reach for many engineers unless they have their hands on massively parallel or supercomputers. On the other hand, the very fast structured finitedifference solutions are limited to simple geometries (this is not entirely true, though!). So, I assumed that many would be "forced" to solve 2D model problems, but the question is how many would be willing to pay for a code like that. (I don't know, do the current commercial codes offer their 2D solvers as a subset of the 3D, so that users don't have to get separate codes?) OK, now that we "agree" that ideally we need 3D solvers but for now we can afford "only" 2D, the question is "how important is it that _that_ 2D solution is obtained accurately and without turbulence models?" (this means a solution with least (or no) amount of empirical data manipulation, and very little numerical diffusion which finitevolume methods suffer from). Does the average user care at all to get an accurate solution to an already watered down 2D model? Thanks Adrin 

September 30, 1998, 16:21 
Re: How large is the 2D CFD market?

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I think it is easier to answer your question in this way: take the turbine engine components design and analysis in industries for example, in the design and analysis loop, you have to do 1D analysis, 2D axisymmetrical analysis, 2D inviscid or viscous analysis, 3D inviscid analysis, 3D viscous analysis, ( and /or 3D multistage transient analysis). A typical 1D run takes one second. A typical 3D run using structured code takes 15 hours. This is for the simple welldefined blade geometry only. ( mesh is always automatic ). Problems other than this have to be defined individually. In other word, 2D and 3D, inviscid and viscous analyses ( or codes ) are being carried out on routine basis. The market for these codes are always there. As for the commercial codes, some provide a 2D option ( code) so you don't have to run 3D code for 2D problem. In the 3D ( or 4D) real world, are engineers running 1D codes ? The answer is YES. Are they running 2D codes ? The answer is YES. Are they running inviscid codes? The answer is also YES. At each stage, they extract unique information from the analysis. But the real need to do analysis is for " competition" in the product market. If you can come up with a better product by just using 2D analysis, you are free to do so. ( something like the secret formula of Coke ). It's hard to make a living by creating a secret formula.


September 30, 1998, 16:43 
Re: How large is the 2D CFD market?

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I don't see a lot of fluid dynamics applications where there is a need for more accurate 2D laminar solvers than those we have available today. Perhaps some special cases where laminar separation is critical could warrant a special "super accurate" 2D code, I don't know.
Most 3D codes offer the possibility to run 2D cases by just using "one layer" in the third direction, or something similar. It isn't as fast as a dedicated 2D code of course. You said something about "2D DNS" in your first post. This might be self evident for you but just to avoid any missunderstandings  to capture any turbulent effects without using a turbulence model you must run full 3D instationary  there is no such thing as 2D turbulence (at least not generally speaking, although you sometime can see that term used in geophysical applications). Just my $0.02 

October 1, 1998, 13:55 
Re: How large is the 2D CFD market?

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There is always a great need for fast and accurate numerical algorithms for solving Euler or NavierStokes equations. The laminar flow is ideal for such method development because you don't have to worry about the effect of turbulence modeling. so you can focus on the method development. The methods available for solving the Euler equations or NavierStokes equations are too slow, and the convergent characteristics unreliable. Even though 2D methods sometimes can not be fully utilized in 3D problems ( the difference between 2D and 3D is not equal to 1D ), it is the starting point for method development. If you can come up with a method which will reduce the computing time by 50% , the productivity is easily a factor of two. ( you don't need a supercomputer to work in this area to develop a fast and/or accurate method). Todays methods for compressible flows calculation ( with or without shocks, low speed or hypersonic ) are "FAR FROM IDEAL". In the design loop, you definitely would like to have the results back in 8 hours ( one day ) or less. Thirty minuites to one hour would be ideal. That's why 3D Euler codes are still commonly being used in the design loop ( less than 30 minuites a run). There are four areas which require special effort: 1),complex geometry ( realistic geometry ) and mesh generation ( consistent with solutions), 2),fast and accurate solution algorithms ( and reliable too), 3), turbulence modeling ( any level, algebraic, 1equation, 2equation etc. , accurate wall parameter prediction: skin friction and heat transfer ), 4), integrated graphic and animation CFD codes ( checkout the intermediate results, and control the solution parameters easily without going backandforth between various codes). The starting point is the 2D where the hardware and the programming software are widely available. ( If you can cut the computing time of Euler solution from 30 minuites to one minuite, you have achieve the productivity of 30 times. I think, it's highly possible that someone will be able to do it. ) The CFDwar is not over, it has not started yet!!!


October 6, 1998, 10:39 
Re: How large is the 2D CFD market?

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> there is no such thing as
> 2D turbulence (at least not generally speaking, although > you sometime can see that term used in geophysical > applications). Hey, there is such a thing as 2Dturbulence Sure it's not 'turbulence' in the conventional sense, but it still exists. I prefer to call it chaotic flow, a consequence of bifurcations in solutions to the 2D NavierStokes equations. The reverseenergy cascade in 2D flows is an interesting subject in its own right, but I agree that it's not always relevant to engineering flows. However, it is valuable in understanding of how fluids can behave in the absence of 3D effects. If you don't understand 2D fully, then 3D is REALLY hard! I would regard 2D DNS as calculating fullyresolved, timedependent solutions of the 2D NavierStokes equations. Of course, this is different to DNS in the usual sense (ie: 3D NS), but it is still direct numerical solution of the governing equations, albeit in 2D. I believe the question is whether 2D calculations WITHOUT turbulence modelling is industrially relevant. As you say, where laminar separation is crucial a highaccuracy 2D solver would be critical. What proportion of 'engineering flows' lie in this category, I would suspect that many do. Thanks for listening Kenji Takeda High Performance Computing Centre University of Southampton, UK 

October 6, 1998, 11:17 
Re: How large is the 2D CFD market?

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I agree, but just to make it even clearer  the 2D DNS you refer to (fullyresolved timedependent solutions of the 2D NavierStokes equations) has no relation to a real turbulent flow, even if the mean flow is 2 dimensional!
Turbulence in real life will always be 3D instationary. 

October 6, 1998, 14:17 
Re: How large is the 2D CFD market?

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I haven't been keeping up w/ the discussion but, I'd like to point out that a number of commercial software offer the choice of running 2D or 3D models. And a lot of unstructured codes are doing very well...Fluent, StarCD, CFDACE+...codes which are very accessible to the user, and cost a few thousand dollars.


October 7, 1998, 02:55 
Re: How large is the 2D CFD market?

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I think there's a distinction between a true 2D code and a commerical code that solves in 3D but with just one grid cell in the 3rd dimension (and symmetry boundaries either side). Is there?
An interesting breakdown would be the proportion of 2D simulations in the CFD software application area classifications highlighted by Jonas. I imagine in an industrial setting the % 2D simulations would be of the order of 5% for most applications. In academia this would certainly be higher. Hey, since when has academia been interested in the real world 

October 7, 1998, 13:10 
Re: How large is the 2D CFD market?

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It is very important to know that market can be created at any time. The product itself does not have to be very good in order to be accepted by the users. So it depends on how you introduce the product to the users ( or the market, if it is already there). It can also be done from the legal side by setting the requirement to use a 2D code before a license is granted. In the 2D world, at least you don't have to worry about whether users have a supercomputer or not. And this is very important. I must say that, the 2D market is still waiting to be created by someone who knows how to introduce a product to the users. Millions of people whould be very happy to use the code if they can derive " something " from using it. That " something " ( unique features ) will be the key to the market. So somehow you need to identify these features in additions to the creation of the 2D code itself. In terms of users equipment, the 2D market is unlimited while the 3D market is limited. Whether the solution of the 2D code is in any way related to the real world problem is not essential to the " 2D market " issue at all. Unless that is your purpose of selling the code. ( Some users may want to display the code on that wall just because it has excellant graphic design.)


October 7, 1998, 18:27 
Re: How large is the 2D CFD market?

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>I think there's a distinction between a true 2D code and a commerical code that solves in 3D but with just
>one grid cell in the 3rd dimension (and symmetry boundaries either side). Is there? I don't think so. But if there is, I'd like to know what it is. My understanding is that there is no real cell in the 3rd dimension. That is only a manner of speaking. "Unit thickness" again is only a manner of speaking. The sevenpoint stencil basically gets reduced to the fivepoint stencil when you choose the 2D option. 

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