What is the Better Way to Do CFD?
 

(1). Even though everyone knows that modern society is derived from the industrial revolution based on the thermo-fluid dynamics, we are still having great difficulties in understanding the physics of fluid flows. (2). Even though computers are now nearly everywhere, and Internet can reach anywhere in the world, we are still having problems in CFD, not to mention the jobs in CFD. (3). So, it seems to me that there is a need to have a general discussion about "What is the better way to do CFD?" (4). Is CFD just to run some existing codes? What is your point of view ? (5). Who should be doing CFD? the school? or the industries? (6). I think, it is about the time to talk about the better way to do CFD, so that the student, the teachers, the schools, the research labs, the government labs, and the whole industries can all benefit from doing CFD. With this, I hope that there will be enough jobs for everyone who is really interested in CFD and we also will be able to see the benefit of doing CFD. (7). So, is there any better way to do CFD? This should cover all CFD related issues and fields.

Re: What is the Better Way to Do CFD?
 

(1). The better way to do CFD can be divided into groups and questions. (2). Do you know everything about CFD? If the answer is No, what do you want to know to improve your understanding of CFD? (3). Do you think your products can be improved by using CFD? If you are not sure, what do you want to know to change that? (4). Have you written a CFD code before? If the answer is No, do you think that it is important to learn how to write a cfd code? (5). If you are using CFD right now, what are you looking for from doing CFD? Do you think that your current CFD activities are the best approach? Are there rooms for improvement? (6). If you are not satisfied with your current CFD activities, then which areas require further improvement? Faster computers? better salary? more engineers? better education? or...? (7). What is your goal of doing CFD? To design a better product? To obtain the best solution? To get a higher paid position? To publish more papers? Are there better ways to achieve your goal? (8). Do you think that the market is crowded with CFD engineers and you have to work hard to stay alive? If the answer is yes, is there a better way to improve it? (9). Do you think that CFD should stay in school and research labs? So you can do researches in mesh generation, turbulence modeling, and numerical algorithm development without worrying about the time schedule? (10). If the code you are using is not producing good results, what is the better way to improve it? go back to school? find someone else to do it? (11). These are just a few questions you can try to answer. And hopefully, in the process, you will get a better picture of how to do CFD in a better way.

Re: What is the Better Way to Do CFD?
 

I believe CFD is ( money driven) just like any thing else in our life today. Although it started in schools as an academic subject some 30 years ago, it became fully commercial recently. i.e. the improvement or the way to do a better CFD is strongly affected by what the industry needs from the CFD codes. In other word, it depends on how essential CFD is for industry. Moreover, before we start this (reform) process we should know what are our klints needs. sorry if my english is not as good.

Re: What is the Better Way to Do CFD?
 

(1)."i.e. the improvement or the way to do a better CFD is strongly affected by what the industry needs from the CFD codes." So, what you are saying is: the industry knows what they need (the code) to do their business? (2). If that is the case, then we really don't have to worry about them. When they need more engineers to perform CFD tasks, they hire more. On the other hand, when the tasks are completed, they fire the engineers.

Re: What is the Better Way to Do CFD?
 

From a company's point of view, maybe the idea of just CFD is too narrow - how to make a better, cheaper, etc. product is the broad question. CFD is one tool, albeit a complex one for a very complex set of physics.

One the other hand, for a narrowly defined, essentialy technical/academic project, there may be 'better' ways. But it might be difficult to generalise as to what they are. For some applications developing expertise inhouse and hiring PhDs etc. may be appropriate while for others using leasing a commerical code for a month and having a graduate engineer do some analysis might be 'best'.

At the moment, I think from a technical perspective it would be nice to have a freeware CFD code, like the Linux OS, which is robust, fairly complete and documented, but for which the source code is also readily and freely available. I'm quickly being converted back to writing my own codes etc., after the difficulties with some commercial codes. But that's not to say they don't have their place.

I even think that their might be room for like a commercial product that is really a collection of modules which can be linked up at will to form a customised user code. Something like Lego for CFD. Patch together your equations, boundary conditions, a matrix assembler, a matrix solver and some post processing tools within an object framework - and well maybe you can have a flexible product. ??

Greg

Re: What is the Better Way to Do CFD?
 

(1). Very good ideas. (2). I am sure that one of the major difficulty in CFD is the creation of a super flexible, easy to use cfd code. Along this line, I think, there is still a bright future. The code itself definitely can be improved in various ways. (3). But I guess, in order to achieve that goal, there must be some practical way to do it. (4). From my point of view, to make a code public, itself is not a problem. I have seen many of these codes in the past.(with some restrictions such as export control. But that is because those codes were developed by government agencies or under government contracts for specific use.) (5). I think, it is not very good idea to withheld information from the users, just because the code owner is trying to protect his financial interest. The consequence is the long period of suffering by the users of the code, and also negative impact on his project or products design. (6). I always think that the management has to understand how to implement CFD, because CFD is the other side of testing. The management probably has a better understanding of the testing. So, that is another area for improvement.

Re: What is the Better Way to Do CFD?
 

What I'm saying is that CFD development at the Universities or research lab in most cases is trying to find an answers to industry questions. That is (in my opinion) why they do CFD these days even if these answers are for questions still to come. i.e. CFD at the universities depends in most cases on the funds from industry or people who needs the results.

Re: What is the Better Way to Do CFD?
 

Who will develop this complete super flexible, easy to use cfd code for free???. I'm thinking about collaboration between the vendors and universities to produce that aforementioned cfd code at a reasonable price (less than $1000 for the whole code). The university will do the solver part and keep improving it according to suggestions from the users. The vendor do the pre and postprocessor parts and also keep improving it. Let us make it a target:"a complete super flexible, easy to use cfd code for less than a $1000", who say yes???

Re: What is the Better Way to Do CFD?
 

hi i believe before thinking of a code we must think of an analytic and theoretical base to be provided for all the people coming into CFD and more generally the complete scope of fluid and gas flow and interaction studies...

best regards

Re: What is the Better Way to Do CFD?
 

I think this question deserves a much wider playing field. What is reassuring is that interest in CFD maintains a good momentum with benefits to all sectors continuing.

The difficulties of fundamental science translation has been due to an inertia of proving its full worth. Our whole gambit of knowledge from basic theory to standards,units and measurements coupled with how best to use it remains still a conundrum.

The diversification of problem areas-space flight,harnassing energy,product fluid interactions,complex shapes,heat,mass and chemical transfer.It goes on.

Can you image when engineers used regularly factors of ignorance [for want of a better term] with material strength having 5 times more than a worst senario could throw up. Look at how FE tackles successfully that sort of issue saving material and cost benefits.

CFD has never been [or will in my lifetime] be a standalone all purpose method of solution. Each field hones its attributes -mixes or matches workable codes against the welter of current knowledge versus dare I say it-areas where were we really don`t fully know what goes in the real physics or mathematics.

If we were to develop[given all the resources] a unifying code what future awaits the next and future generations. Robot coding ,Robot design and Manufacture. Thankfully the real situations remain ahead of the best models we can throw at them. We are getting closer but the future remains a mystery still.

The pioneers of CFD used imagination,flair,met setbacks resolutely,never promised to deliver a unique standalone science-but adapted to demonstrate the worth of their scientific based work for problems of the era like defence or leading their respective fields and staying ahead of the global competition, winning markets.

Re: What is the Better Way to Do CFD?
 

(1). It's not going to be written by the existing commercial cfd codes for sure. So, at the moment, we will have to assmue that it will be written by someone (a human being). I am not saying it's easy or practical at all. (2). Between vendors and universities? Unfortunately, Verdors are for-profit organizations, and universities are non-profit organizations. Both can not think at all. They sure can spend money at very fast rate. (3). I think, that is one idea, but who in the company or university should create these code or tools? Along this line, nothing can be done, until the person(s) can be identified. (4). Before that, one need to identify what this person(s) should do to create this super flexible code(s). In other words, what are the essential parts of this super flexible code(s)?

Re: What is the Better Way to Do CFD?
 

(1). Well, good thinking. But it is not 100% correct. (2). First of all, the graduate students need the degree, so they need to write a thesis or a dissertation. For that, they need a subject. In fluid dynamics in general, there are three approaches, one is analytical, another is experimental, and the last is CFD. (3). With the subject selected, the student can start working on it. If the student need the financial aid, he can get a loan, or scholarship. And if the professor is working on the same subject through a project, the student can also work on it and get paid. (4).It is possible that sometimes a company will contact a professor for his opinion or give him a small research money to work on it. This seem to be a good place to start looking. What are these companies? Do they have the money to support the university research? Do they have the infrastructure to learn, absorb and use the technology developed? I mean, if the student work on the project, what is the possibility of getting a job when he graduats from the school? (5). In this case, the future seems to be more important than doing the research or getting the degree. You don't want to increase the jobless rate, right? So, what is the other end of the pipe-line? A perfect cfd code selling for $1000, with no one buying?

Re: What is the Better Way to Do CFD?
 

(1). Well, I have noticed that many engineers,without good training in CFD, are learning how to use commercial cfd codes. (2). Should they be sent back to school first, so that formally trained CFD engineer can have the opportunity to solve the problem more efficiently? (3). What courses should be provided in school to properly train a CFD engineer or researcher? And to what degree? (4). Can we list some fundamental courses for CFD students? What do you think should be the minimum requirement for a cfd student?

Re: What is the Better Way to Do CFD?
 

(1). There is definitely a huge difference between the structure/stress analysis and CFD. This comes mainly from the convection term of the governing equations. (2). So, apparently the effect of the convection term varies greatly from problem to problem. But that does not mean that there is not solution to each problem. (3). It simply says that each problem (definitely includes the geometry) will have to be addressed individually. (4). Following this line, the idea of the super flexible and easy to use cfd code(s), seems to have a lot of technical problems to solve before it can become practical. (5).It seems to me that we need to address the technical problem of the flow to be solve first, then write the code to solve it. Not the other way around like what some people are doing right now, that is first develop a super flexible and easy to use code, then find an application problem for the code. Is this what you are thinking?

Re: What is the Better Way to Do CFD?
 

I think the idea of universal application is too ambitious and more importantly, not generally worthwhile.

Individual users/companies normally have a small set of related problems to solve. No individual/company etc needs one tool to solve all of these small related problems - it just doesn't make sense.

Having said that, there is a trend which will continue to add more complex phsyics and geometry to problems to be solved numerically. This is driven by a) faster computers b) more available codes and c) some new knowledge of the physics (although this is generally pretty small/secondary). a) and b) will continue and in some sense feed off each other. c) grows slowly thus most of these available codes have fairly primitive models inbuilt, wrt to the state of the art - despite what they might say in the brochure.

You just have to look at some of the old research codes from Lawrence Livermore lab., to realise they had unstructured grid adaption nearly two decades before commerical codes! And the current ones are where cfd is headed.

I suppose the need for general purpose codes is to a large degree driven by economies of scale. Its probably easier and cheaper to implement (initially), maintain and support one code than ten. For some problems, like combustion, you need a lot of these sub-models to get any solution. On the other hand, making all the sub-models work together is a significant problem.

Just look at the yet-to-be-released Fluent 6. That's been mooted for well over 1 year now and will still don't have a release date. There must be some major difficulties getting it all to work, which is very interesting given they already had most of the models implemented in an older, but structured code.

The idea of integration with fancy A.I. stuff sounds good. I want to do something in this area too, but really I think its more important for engineers to develop their own intuitive ability for specific problems than seek a brute-force all in one solution. Having said that, it seems to me that more automated, partially optimising methods are a good way to give engineers more time to spend thinking about the problem. I really didn't go to uni to spend 30% of my time creating mesh nodes, and recovering from software crashes!!!!

Greg

Re: What is the Better Way to Do CFD?
 

We cann't build a super flexible code to solve all the problem, why? because of the new theories (every day) which explain some of the most complicated problem for example: turbulence. That is why I believe that we should build it in a most complete shap and keep improving it.

Re: What is the Better Way to Do CFD?
 

we meight achieve this by good marketing people for our target price to be accepted by the profit companies.

Re: What is the Better Way to Do CFD?
 

I believe that the schools should focus on the mathematics part of CFD.i.e. the theories, the mathematics, numerical analysis, the modules and the solver as a whole.

Re: What is the Better Way to Do CFD?
 

No, if there is a SFUF (super flexible user friendly) code for $1000, this will promote the companies to explore the approach and if they get rewarded they will invest more on CFD and hire more engineers. It is like the big stores when they sell for half price and they make profits more than 500% because they sell 5 or ten times. What do you think?

Re: What is the Better Way to Do CFD?
 

(1). I'll be away for a few days, at the same time, keep writing, and see whether we can get a rough model of how to approach CFD in a better way.

Re: What is the Better Way to Do CFD?
 

You are quite correct to highlight the differences between solid/liquid and gas- gradual displacement/volume changes rather than rapid complex physical and chemical/heat transfer changes dealt with in CFD.

In the FE viewpoint I was drawing attention to new approaches compared to historical known areas of ignorance where there was no back up data or true understanding to incorporate easily into a design.

In a strictly scientific way CFD can be adapted to cover problems of all types given that we understand as fully as possible the problem physics at all times.

How far forward are we in direct data feedback from a test bed scenario to automatic code changes for simulation online realtime.

In words can we learn directly from the test bed and produce a realtime parallel simulation - algorithmn and matching CFD Solution.

Re: What is the Better Way to Do CFD?
 

Ok, since I seem to be one of the few CFD students here, I will share my thoughts. I'd love comments on the classes you feel I'm missing or ones you think are a waste of time.

Background: I feel mechanical eng., chemical eng., aero. eng. are all good starting points (there may be more).

Necessary classes: Thermodynamics, Transport phenomenon, Conduction, Convection, Numerical analysis, Partial differential eqns, and Computer programming.

Helpful classes: Kinetics, CAD, Computer graphics, Technical communications, Aerodynamics, and Viscous flow.

These can be completed in most universities with a BS degree. However, to gain the skills to solve in depth problems, I'd rather see these people with an MS degree.

Re: What is the Better Way to Do CFD?
 

John thanks for a great question. Since we are engineers we probably need to approach your question from an engineering point of view. This entails two things the technical aspect and the commercial aspect. Some may disagree that the commercial aspect is relevant but I'd argue that it any engineering endeavour that in the long run (whatever that is)isn't commercially viable is doomed to failure. Just look on those who've tried to design and sell flying cars: technically sound idea but commercial disaster.

On the commercial side CFD must be recognised for what it is: it is a design tool nothing more. Ithink the fact that many CFDers spend a lot of time in school where the commercial aspect of engineering is ignored leads to a lack of consideration of the commercial aspects of CFD use. Firstly let me sayt that CFD is obviously a commercially useful tool. In almost any mechanical device there is some need to perform fluid analysis. This also applies to chemical processes, civil engineering project and environmental and biological sciences which are having more effect on our lives every day. So the market for CFD is there.

Having established that the market is there how do we popularize CFD or how do we get CFD to the point where it is as widely (or nearly as widely) used as say FEM for structural analysis? I think the answer to that is many fold. We need to have engineers who are cognizant of the usefulness of CFD and are skilled in its use. Fundamentally this requires us to have young engineers properly trained in plain fluid mechanics ignoring completely the C part first. Secondly we need to have commercial software that can solve the variety of problems in different industries where CFD can be used. Commercial software is necessary because if someone can't make money selling CFD codes then we won't have CFD codes to use. Wide applicabilty doesn't mean that the codes have to be huge one-code-does all types that we often see today because in many cases the codes are Jack's of trades and masters of none. Different industries require different and often very specific functionalities that would only be useless cost to another industry. Also in some cases a given industry may only need a very simple code, however these are often not available. How many commercial panel codes can you name off the top of your head? Or how many commercial codes offer simple boundary layer analysis?

On the technical side we can again use the commercial structural FEm codes as a model. I know FEM is simple compared to CFD but still we can learn from them. Using CFD is a lot more than just the solver the FEM guys realized this a long time ago. Pre and post processing are the most important steps in a CFD analysis because (1) preprocessing is where you the engineer can affect the solution and (2) postprocessing is where you determine if the answer make sense, and extract the information that is off use to you. If I have a choice of two CFD codes that give me similar results but one takes 2 months to preprocess and the other takes two days I'll take the one that takes two days every time. I've often heard people say "my code runs faster than yours and uses less memory" but in todays world where memory and computational power are relatively cheap compared to the cost of an engineers time such a statement is of minimal importance if the first code requires more engineer time than the second. In post-processing engineers need to extract the data of interest. If management gives me a target lift to drag ratio of 15 and I get 15.1 I could probably care less what the detailed flowfield looks like because I know it's probably pretty damn good. If my commercial code requires me to write whole bunch of scripts to extract the lift and drag I'd probably can it in favour of the code where it's two mouse clicks away (all things being similar). Similarly a turbine designer wants to know where on his map is his stage running right now to that he needs to extract the pressure ratio, corrected flow, stage work and efficiency in quick order - preferably automatically.

In addition to the mechanics of the running the code engineers also need to be able to optimise their designs, account for variation and interface their design inputs/outputs with colleagues in other disciplines. I have a buddy who was doing structural analysis on a turbine blade and it took him half a day to map tempaeratures onto his structural model! Not only that but the process was error prone due to the number of manual steps required and this is a routine analysis for a structural engineer. The FEM code vendor needs to automate this process. Similarly if i'm a wing designer I need to be able to take my aeroloads and put them on my structural model quickly and reliably or better yet solve the coupled problem.

Last but not least from the nitty-gritty solver point of view we need to both develop and disseminate new computational schemes: everything from turbulence models, to linear equation solvers to parallel algorithms, to flux techniques etc. I think the dissemination is as important as the development becasue it's all well and good for some guy in a university to say "I've vome up with the most fabulous flux scheme that captures shocks in teo grid points, has minimum artificial dispation, shows no oscillation and runs really fast" but if the commercial vendors can't put into the code that I use because the professor hasn't published any readable papers on the subject or the code vendor can't be bother to put it in his new code because he was working on a bunch of wizards or something then it won't benfit me any.

In general we need codes that have sufficient attention placed on usuablity and technical sophistication and right now in the commercial world there are few.

Re: What is the Better Way to Do CFD?
 

Well the assumption here is that it all works and therefore that the buyers will be happy with the product.

The potential risk is that you sell a big lemon and ruin your chances for the future. Then this is worse than if you had a planned, staged and simpler product which could do something WELL. Rather than a product for all, but capable for nothing (or little).

If it works, ok. Of course things are never quite so black and white in reality, but I think you get the point. The code vendors push cfd codes - and I think they have a really good product. But even just yesterday the internal support guys sent me back my question, commenting - "I'd like to know how to do that too". And its "their" code!! So you can be disappointed.

Obviously there's been lots of progress in this direction with regard the codes. But wil still need rigour in the training and science for us (engineers).

Greg

Re: What is the Better Way to Do CFD?
 

Clifford I think your points are excellent.

I think to some extent the current codes try to address all industries and provide general tools. By doing this some of the pre, post and solver technologies are then a compromise between what is required for 'your' problem and what is required for 'everyone' else's.

Its a bit like Micorsoft Word - nobody uses more than 20% of the features, but apparently, everybody uses a different 20%.

Thus in general codes you need to add your own customisation - if the vendor can provide tech support on how to do it.

I don't see this changing quickly, though a suggestion would be to somehow split up the task and allow different vendors to develop the required bits for different problems/industries. By this, we need standards, and then using these standards we could perhaps have an object framework for coupling the different parts together. I realise this is a mammoth job and not something that's going to happen quickly. But it might in time. We have already seen a standard for CFD data storage and interchange (CGNS?) which is available in some codes and perhaps more in the future. I see no reason why you can't extend this principal to include most parts of the complete package - pre, post and solver. But what I really mean by these components, are much smaller components - ie say a turbulence model, or a model for electromagnetism, or even a database of heat and mass transfer correlations. These could all be assembled somehow. Perhaps a simple metaphor is the (1) AVS program or flowsheet modelling program like (2) HYSYS where you link up visually different components to model a process (in this case a 1. post-processing process and 2. chemical plant process).

Can we do CFD by linking the required parts together?? General cfd allows us to do this a bit, by pushing buttons, but its not very flexible, really.

Greg

Re: What is the Better Way to Do CFD?
 

In truth Greg some of the difficulty the commercial vendors face is that they are small. Sometimes we forget that. A company can have a fancy web site and advertise everywhere and give you the impression that they are a large company but they may only have 40 engineers and maybe 5 to 10 a writing code. I believe in the future we'll see some mergers and acquisitions in the CFD business that hopefully will give some of these companies the size they need.

Re: What is the Better Way to Do CFD?
 

(1). Super flexible means that it can be changed into many other forms. (2). And there is a possibility to turn that into infinite number of configurations. (3). The easy to use part simply says that the user does not need a handbook all the time. He can learn some basic operations and then he can figure out intuitively the next operation in using the program. (4). So, super flexible and easy to use is something achievable. (5). The reason why you said that "We cann't build a super flexible code to solve all the problem" is because you are thinking about "understanding the physics of turbulence". I think, if one is still trying to understand the physics, then apparently, he is not going to write down the equations and the code. So, we will have to be realistic and practical, when developing this super flexible and easy to use code. (6). Obviously, we are not trying to solve "all the problems in the whole world". With that understanding, I think, the super flexible and easy to use code is not just a dream. (7). For example, if you are ask to add two numbers together (9876543+1234567), do you have to learn the math for these two number first? No, you don't. You apply only the rule of (1+1=2). And right away, you can add any two number together. (8). Perhaps, you are thinking about solving the physics of the problem instead of solving a problem with known physics. And I think, this is always the limit of a code. A code can only repeat the same process, it can not invent the new physics. That part must be done in the research department.

Re: What is the Better Way to Do CFD?
 

(1). I think, this is being done all the time at different levels. (2). In any design, we are basically dealing with changes in configuration. That is: which configuration is better. (3). In most cases, this is done step-by-step. In this way, it is easier to control the project. You assume a configuration, predict the result, create the data base, study the implication or meaning, then make a conclusion for the next change in configuration. (4). This sequence could be programmed into a code easily. In this way, a better configuration will be derived. (automatically) (5). Sometimes, there is a problem with this approach, because the person who has the power over the project would like to know why, and also he like to give direction to the future development. So, fully automatic code is not suitable for an organization. (6). If a person can make a better design, then he sure can write down his way of thinking step-by-step into a code and make it automatic. The problem is more on the implementation side, rather than on the technical side. After all, on the other hand, if you don't know how to get a better design (I mean the logic), then it is almost impossible to write a code. (7). Some people are better thinker, so, the codes they derived will be different in flexibility and in user-friendliness.

Re: What is the Better Way to Do CFD?
 

(1). I think, CFD is " Numerical Analysis and Mathematical modelling in Fluid Dynamics". So, numerical analysis is basic requirement. (2). Mathematical modelling means that the physics however complex or complicated, must be put into a well defined mathematical model form, whether it is the geometry of the object, model of turbulence, turbulent reacting flows or multi-phase problems. (3). I think, the poor performance in CFD simply means the poor understanding of the numerical analysis, and the poor capability in the modeling of physics. (4). And if the flow is laminar, one can eliminate the turbulence modeling. In this case, it can be simplified to just numerical analysis. (5). Whether the analysis should be done only in schools or not, it really depends on the environment. In some places, the research is mainly done in universities, and little in industries. But in other places, at lot of higher level research are carried in industries. (6). So, I think, the school should at least learn, or teach numerical analysis. As for the physical modelling (or mathematical modelling), it will depends on the application itself. This is because, for some problems, the industrial experience is very important to understand the physics behind so that he can create a proper model.(in mathematical form for use in the code)

Re: What is the Better Way to Do CFD?
 

(1). At the BS level, you really don't have the time to think indepently in terms of the problem solving and also to carry out the necessary steps to obtain the solution. (2). Let's say the you have a simple journal bearing problem to solve. This problem is fairly common in real world application. You see it everywhere, from your car to large machines. Given the training of a BS, can one write down the correct governing equations, the necessary coundary conditions for the square cavity flow problem? (3). If you pass that step, then the next one is to turn it into algebraic form so that you can solve it. This requires the knowledge of the partial differential equations and the numerical analysis. (4). If you pass this step again, you are facing two problems, one is the mesh generation and the other is the code development. Even though, the mesh generation using Cartesian mesh is easier for the cavity flow problem, it still necessary to do stretching near the wall. You could use unstructured mesh though, but the mesh generation would be more complex. (5). Assuming that you know how to write the code, and obtain the converged solution, you will be facing the problem of reading the results. This could be in digital form, line plots or contours. At this point, you are comleting the loop and connecting the results back to the problem. The problem in this case is the journal bearing problem. And I think, the basic knowledge about the operation of a journal beraing is required before one can make use of the CFD results. (6). This process is likely to take one way beyond the BS degree, I think. Someone may be thinking that a commercial code should be able to solve all of these problems, and there is no need to go through all of these troubles. Well, that could be another approach in the future. But still, the code is lifeless, the code does not provide warranty, only the user can think and make decision. The degree of involvment could reduce the time, but not the responsibility. So, training is essential.

Re: What is the Better Way to Do CFD?
 

(1). You can use a small digital calculator anywhere to perform algebraic calculations. So, you should be able to do the same with a super flexible and easy to use CFD code. (2). You can drive a car in one city, you can also use the car to travel to other city. (3). A car and a calculator perform the operations through mechanical devices and computer software. So,likewise, one can develop a super flexible and easy to use code to perform various tasks. Is a car universal in terms of its ability to travel to different parts of a country? (4). It wasn't possible a couple of hundred years ago. But it is practical today, even with a lot of computer controls in it. (5). The important thing to remember is: we are not trying to emulate the god. After all, a car is a car in the last one hundred years. The basic form does not change much. This should be applicable to our super flexible and easy to use code development. (6). After all, we are not expecting a car to be a ship or an airplane. This could be a very important guideline.

Re: What is the Better Way to Do CFD?
 

(1). Well, that's a good thinking. (2). But that is only you are sure that there are five or ten more customers out there willing to come back for that price. (3). If I put a five dollar watch in a large box and seal it, then put a picture of an expensive Swiss watch picture on the box, would you be willing to buy it for one thousand dollars? (you will be able to see the time from the outside of the box, but you can't touch the watch. not even when the battery is dead) (4). If you are looking at the larger return in the future, it is probably make sense to give away the super flexible and easy to use code at the begining, like the internet code, internet connection, e-mail, etc. I don't think "free product" is a good idea. It simply means that for now, it is being paid by someone not you. And if "free product" can promote bigger sale of other products, then it is an excellant idea. What do you think?

Re: What is the Better Way to Do CFD?
 

(1). If you are asking the cfd code to be flexible, then it is hopeless. That is because, a code is just the description of your thinking process to solve the fluid dynamics problems. (2). So, you are asking yourself whether this kind of process is possible or not. (3). The answer is very simple. If you think you can solve the problem, then it is possible to translate the process into a code. (4). The hard part is, in most cases, people do not have "experience in their data bank-in brain" to make the correct conclusion. (5). Without such experience stored in the brain, it is unkely to translate anything into a super flexible and easy to use code. So, car was invented, airplane was invented, light bulb was invented, etc... (6). At some point, something will be invented which is usually considered impossible before. The need is to think something impossible first.

Re: What is the Better Way to Do CFD?
 

John, I'm not quite sure what you're getting at.

I was thinking, (mainly academically) that perhaps one could build a cfd system in which one connected a set of well defined sub-models and sub-modules together. This is in essence what today's commerical cfd codes do, but I was thinking that it might be useful to allow the user much more control over how these cub-somponents were put together - in current codes this is decided by the vendor. And maybe a after-market for add-ins might develop.

Consider an operating system. It provides a back-bone of services etc for applications to use and share. Is it worthwhile to consider a system which provides similar utility for cfd type problems, in which case the 'applications' would be a set of connected numerical modules etc.

There exist some codes, Fastflo, in which the user can actually describe the pde's to solve and the algorithm thru a special language in which one assembles numerical operators together. I was thinking along these lines, with some additional levels of abstractions.

As clifford says - it may be difficult to achieve commerically - but at this stage I'm not too worried about that aspect.

Greg

Re: What is the Better Way to Do CFD?
 

(1). You first build a house, then another house. then pretty soon, you have a row of houses. So everything looks fine. (2). Then as the population grows, you build another rows of houses , and somehow there is a street. For a row of houses, you don't see a street. But with two rows, the street is created for free. (3).When the population grows bigger, you have a town, which soon becomes a city. And you have cars everywhere. (4). If you drive a car at 15 miles per hours on the streets of this city, is it safe? I think, you will have accidents at every place. and you would say such big city with cars is impossible. (5). It is impossible. Because cars will run into each other at 15 miles per hour in a city. You probably don't agree with me at the moment. But that's fine. (6). If you look at the modern city, you see extra things, on the streets. That is the traffic control lights. It takes extra things to make it work. (7). This is one of the thing I am trying to point out here. Your idea is not working, because there is something missing in your planning at this stage of thinking. So, a very detailed plan must be carried out first before his idea can be translated into reality. It is true for making a code, career, a company or even a nation. It simply says that the failure is the consequence of inadequate planning. (8). A code came out of the vendor's machine will have negative impact on the users if it is not well planned. (9). And since a code can not think by itself, the planning has to be done by human being. This is the reason why running a code alone can not solve the problem. (10). I alway think that the best way to destroy a person, or a company is to ask the person or the company to use your code. In this way, they will have to depend on you. At the same time, you will be very busy asking the same stupid questions over and over againg. In addition to this, you will have time to do thinking, and he is not going to have time to create his new ideas or methods. Then the distance between the race will increase. (11). You see, it is a war. Somewhere along the line, you will have to stop that stupid way of doing thing and let your brain do the thinking for you. The failure usually is determined right at the start, when one decides to take the short cut (as defined by the person at that moment). (12). I am trying to expand the view somewhat, but it is essential to know that once a person accept the slave state, the failure is determined. (13). If you don't have a plan for a working code, then any level of thinking is not foing to give you the needed answer. (14). Sure, you could ask someone else to create the needed components for you, and add your logic or components to it. But, what is your goal? I think, it is the solution to the problem from the code, so that it can be used for your design. In reality, if you don't get the right answer to your problem, the responsibility is yours, not the person who provide the components. (15). The famous failure of the Mars Probe due to unit system conversion simply says that " every piece of the code or machine must be exactly to make it work" (16). And what I am trying to say is:your idea of making a program modular (like building a city) can become a reality, only when you also have a plan to design something like the traffic control system for a city. (17). If you fail to consider the traffic control system in the city planning, the city will failure, not because such city can not be built, but because there are critical parts missing. (18). If the city planner show you that the city without traffic control is working at car speed of two miles per hour, can you say that it will work when people are trying to speed up and get to work in a hurry? (19). In other words, people are taking high risk, but they are suffering and the failure will teach them how to do CFD in a better way. (20). Anything can become a reality, only when you have a complete plan to make it work. (21). In real world, thing will take its own course, even if the initial condition is not right, because the world is finite and to some degree it is self correcting. (22). But this is not the case for cfd programs and cfd solutions. Like the Mars Probe, one single factor can determine whether it will succeed or not. And to make it work, more training and experience definitely will help. (23). It is difficult, because you don't know the answer. Not because there is no answer. And many CAD and graphics oriented programs nowadays can accept plug-in modules, because it is designed to do so using object-oriented concept and programming. (24). I think, your idea is being used in computer graphic world already.

Re: What is the Better Way to Do CFD?
 

(1). I think, at this point, there are serval issues raised. (2). One is the code should not be free, and it should be priced at $1000. This is one better solution to the current CFD industries. So, we can say that the current commercial CFD codes are over-priced. Because of this, the CFD suffers. A CD costs less than one dollar, so charging anything over $1000. is excessive. I think, it is a good idea to lower the commercial CFD codes. Although the number $1000. is kind of arbitrary. (3). a BS degree is the minimum requirement to get into the CFD field. a MS degree has a potential to get a good solution. But I think, a PhD in CFD would be ideal. I am thinking about the extra time provided by the PhD program to do hands-on exercises. Without that extra time, one will be using the employer's time later on to do the same thing. (4). The development of a super flexible and easy to use cfd code seems to attract some negative comments. I think this is because I have not define the exact specification yet for this code. If we let the common sense to guide us, then apparently we are not talking about creating a car which can also fly like an airplane and sail like a ship. (5). Even in a school, there are different departments. And in the same department, there are usually several different fields. We are not talking about creating a cfd code to solve both the pump problem and the combustor problem at the same time. And this seems to be the weakness of the general commercial code vendors, because you almost have to hire code programmer and developer from every field of a department, and every department of a school. (6). And this seems to be the case with some vendors. It seems to me that as a first step to do better cfd is to define the field first. It is nonsense to talk about cfd for weather prediction and the pump design at the same time, even though it is fun to listen to the voices from different field of applications. This kind of focus is important. And you can see why by looking at the desk top computer and the laptop computer. And I don't think it is a good idea to develop an assembly line to produce desk top computer and the laptop computer at the same time, or even different time. (7). We will be better off in the future to include the field of application in the specification of this super flexible and easy to use code. I think, within this context, the super flexible and easy to use code concept can still apply. Or you probably have different opinions and ideas to say, I hope.

Re: What is the Better Way to Do CFD?
 

(1). There is really another bigger issue in CFD, that is the code-user interaction. (2). In the case of a digital calculator, the user is not interested in the hardware and software underneath the cover. He is mainly interested in the input and the output. (3). This is also the case for a car, except for those who are involved in racing. No one really is interested in improving the gas milage of the car his is driving, and trying to look underneath the hood. (4). For CFD, this is different. Here, one is mainly interested in the better way of getting more accurate results. Therefore, every bit of the detail is critical to that goal. (5). If you have been reading the forum, you should already have such feeling. For example, no one is really discussing about the issue of changing a few degree of a pump inlet angle and getting x% increase in efficiency. On the other hand, most people are asking questions like, how to get converged solution, which model is better for his problem,... and so forth. (6). So, the statistical data shows that users are interested in every bit of the code, because he is having trouble with it. I think, this issue must be resolved first, otherwise, you will end up like a cfd code slave asking endless questions. I think, it is miserable for a CFD engineer to be traped in that position. (7). So, this idea of a super flexible and easy to use cfd code, must solve this code-user interaction problem first. (8). Unless, of course, you love this type of work. I am looking only from my point of view. So, I could be biased.

Re: What is the Better Way to Do CFD?
 

John your analysis in this fascinating question indicates that given the right impetus of ease of availabilty at a sensible cost to the user CFD can provide the solutions to a whole range of scenarios.

You have concluded that a PH D backround will prove more helpful than just a B Sc for the more demanding areas of physics flow related problems.

You have also ascertained that a super code could very well emerge provided that the full data of the background work of the associated problem area has been correctly performed and moreover well understood.

What is very difficult to assess is the in house code maker versus a black box containing numerous side packages that is user friendly but likely to cause headaches because it is too general and open to misuses.

I sense that you are leaning toward a CFD much like it is now but with better[significant?] refinements toward better accuracy and reliabilty.

What also is worth reviewing is: 1. what is the biggest advantage of CFD. 2. which type of problems lend themselves to CFD. 3. given the resources what would cfd users like to happen to stimulate its uses. 4. who currently leads and drives CFD -research or industry. 5. what is the biggest problem currently facing CFD. 6. would numerically computed fluid dynamics[NCFD] be more helpful and better name than just computer fluid dynamics[CFD].

Re: What is the Better Way to Do CFD?
 

(1). I realized that CFD is at its cross-road now. (2). And your comments and questions do make a lot of sense. (3). Since I am running out of my free Internet time, I will have to answer your questions off-line first and copy it back here. (4). I don't have a fixed plan or picture right now. It is like that there will be several possible models for CFD, including its new name.

Re: What is the Better Way to Do CFD?
 

Look at the market around us, they use the same strategy. Once again, this target needs a good wells to carry it out if we still have some.