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R.K. Bansal April 17, 2001 09:23

I am new to this discussion group. I know very little about CFX. However, I have used FLUENT for multiphase flow simulation quite some time ago. My company is considering obtaining a seat of either FLUENT or CFX. Can anyone give me a comparison of the two. The application is in drilling for oil and gas.


Greg Perkins April 19, 2001 22:06

One important aspect is technical support. I'm using Fluent and to be honest I'm not real happy about their level of technical support. These experiences though do depend on the types of problems and your questions.

For complex multiphase and user code questions I've found answers from Fluent hard to come by.

I'm not sure if CFX/AEAT is any better but its worth looking into...


Li Xinfeng April 22, 2001 04:21

In fact, I think the CFX's technical support is the best in the CFD software. But I think it depend on who u ask for.

G.A.L April 24, 2001 15:13

Do not go with CFX!!! Our company got it 2 years ago and it has been a dissaster.

- Technical support is bad

- The code has lots of bugs

- The post-processing is the worst I have ever seen.

It is very difficult to perform calculations such as integrating fluxes over surfaces, etc.

I have experience with Fluent packages and they are MUCH better. Excellent post-processing and fairly good technical support,

John C. Chien April 24, 2001 17:43

(1). I am happy that currently I am not using any of the commercial cfd codes. I think, the support service is very critical to the day-to-day operation of the commercial cfd codes. (2). There are two parts of the problem, one is the operation of the code, and the other is the solution of your technical project. (3). The former, you can get the names of the support engineers or the technical service and call them or e-mail them on the day-to-day basis.(try this out and know your support engineer, do not wait until you are in big trouble.) (4). The latter, you will have to explore your problem and their experience first, to see which vendor, consulting firm, or the code can better serve your need. Based on my experience, in this area, I had to do a lot of home work exercise and work out the details. This is because in most cases, the support engineers know only the operation of the code but not the technical part of your problem. (5). If you are interested in solving your problem, make sure that you do the search first to see which group can better serve you. (I mean, the group which has the experience in your technical problems.) It does not make sense to use your time and problem to train your code support engineers.

Li Xinfeng April 25, 2001 00:13

I doní«t think so. In fact, the cfx4's new post-process is very good.

Dan Williams April 25, 2001 01:09

Hmm, pretty scathing remarks. I'm sure many would completely disagree with you. Which CFX package are you using? Integrating boundary fluxes is easy in CFX-TASCflow. I'm not sure about CFX-4.

Why is technical support bad? Unresponsive, non-existent, not useful, etc..... Do you care to elaborate rather than making an arbitrary statement.

What bugs have you run across, specifically?

I agree Fluent can be very nice. But if it doesn't blow up (read the user forum), you'll usually wait until the cows come home for the thing to converge (also read the user forum), and also read the user formum to find out about some of the crazy things you have to write user source code for. (eg, a transient boundary condition, or initialising velocity with cylindrical components). Come on.


Greg Perkins April 26, 2001 01:54

I suppose the best is to get both and evaluate them both for your problem.....

anyone done this???


joseph May 8, 2001 05:33


If it is multi phase then it is got to be CFX.

sure fluent looks good and easy,not technically,

it will be long before you get a result.

I will agree with Greg and Dan ,as far as technical

support is concerned these (CFX guys) guys are really

clear and with quick responce, believe me coz I was in AEA india,and I have seen

their dedication to the costumers.

All the best any way in you selection.

Regards, joseph

pop May 8, 2001 10:27

Hi Joseph

Did you try to benchmark the results of CFX 5.4.1 (the latest from AEA). The package is failed to model as simple as the inlet region of a circular duct. In cases with laminar flow the pressure drop and Q are not bad but at the point you hit turbulence or transient it is missy. In a contact with AEA they have no explanation. Do you?

Dan Williams May 8, 2001 21:49

I've done this with 5.4.1 and it predicts pressure drops perfectly, both turbulent and laminar.

In fact, I believe the documentation includes an example which compares friction factors to those obtained from the the Moody digram and the accuracy is excellent.

What sort of problems have you had exactly? There are a number of things that you could be doing wrong with trying to solve this problem. How did you set the problem up for example? Did you use periodic boundary conditions and a momentum source to set the pressure drop (which will always give a good answer), or did you just grid up a pipe of length L and let it rip. If so, then did you make sure that L was alot longer than the entry length needed to develop a fully turbulent profile? If so, did you only compare the pressure drop in the fully developed region? What boundary conditions did you use to ensure that a fully developed profile would occur? etc... Hopefully you get my point, i.e., that solving these problems properly is not as trivial as it might seem at first.


lightwind July 3, 2001 08:54

I agree with you!!

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