[aerospain]

Hi everyone,

I'm going crazy and decided to post to see if someone could help.

I want to simulate the flow of a cylinder with its axis parallel to flow direction, imagine a disk of a given thickness with its flat faces normal to flow direction.

I have started with a 2D (axisymmetric) domain and it has worked just fine in Fluent. No problem whatsoever ...

Now, I create my 3D domain by revolving around X-axis (flow direction), export 3d unstructured mesh to fluent *.msh, open it in Fluent and BIG CRASH!!!!

This is the summary of my problem. I have gone through the relevant tutorials in ICEM, have watched many videos in YouTube and read info/tutorials/pdf/... in the internet.

Cannot figure out what I'm doing wrong!!!

Any help, please?

[shereez234]

Can you post some pictures of the problem

[aerospain]

No need of pictures as my problem is well stated:

I have a 2D axisymmetrical domain that I want to revolve and export to Fluent.
I can export the 2D axisymmetrical domain to Fluent and perform simulations with no problem at all.
When I open the 3D domain in Fluent I get an error.

Answer:

Someone to post the steps I need to follow for success. (I have watched all youtube videos, and read all tutorials in Help, and I'm missing something)

Thanks!

[shereez234]

oh boy. You ask for help and you don't want to give out any information. what do you mean by BIG CRASH. if you can't post pictures for whatever the reason atleast post what is the error message? as far as i know Fluent can give out thousands of errors and one could not guess what is your error in a go

[aerospain]

oh boy

Let me rephrase my problem then: "How can I create a 3D domain with revolution and be able to export to Fluent?"

You see! My problem is not that I assume to be following the correct procedure for something and getting a strange mesh shape in the end. It is that I cannot get to a solution because I'm following the wrong steps after creating the axisymmetrical domain to be revolved. So, I'm asking for the steps.

It's not all about pictures and misleading error messages. I like to KISS

Thanks!

[Far]

Originally Posted by aerospain

Hi everyone,

I'm going crazy and decided to post to see if someone could help.

I want to simulate the flow of a cylinder with its axis parallel to flow direction, imagine a disk of a given thickness with its flat faces normal to flow direction.

I have started with a 2D (axisymmetric) domain and it has worked just fine in Fluent. No problem whatsoever ...

Now, I create my 3D domain by revolving around X-axis (flow direction), export 3d unstructured mesh to fluent *.msh, open it in Fluent and BIG CRASH!!!!

This is the summary of my problem. I have gone through the relevant tutorials in ICEM, have watched many videos in YouTube and read info/tutorials/pdf/... in the internet.

Cannot figure out what I'm doing wrong!!!

Any help, please?

Hexa (blocking) or tetra mesh? Are you using rotation option on mesh in edit mesh or not? Are you following some threads in the forum for similar problem?


For hexa, this can be helpful to you : https://www.youtube.com/watch?v=JxUnEMbGBL4


http://www.cfd-online.com/Forums/ans...locking-2.html

There are many other threads on the same topic by Simon and Diamondx. Search them as well, they are very much helpful on subject.

[aerospain]

Thank you Sijal,

I see I had a piece of information missing. I would like to revolve a tetrahedral mesh, so it is seen as a structured mesh.

About reading other threads in the forums ... Yes, I have looked in other threads in this forum and others in this site.

I have replied to your private message too, and I can say it publicly as well. I have not used an inappropriate language anywhere, and I would like a second moderator to review the threads. If we are getting too sensitive about things, I feel offended for being pointed at as someone with no manners.

I appreciate everybody's time and help. Specially yours when no pictures were needed to point me to those links.

[Far]

Originally Posted by aerospain

Thank you Sijal,

I see I had a piece of information missing. I would like to revolve a tetrahedral mesh, so it is seen as a structured mesh.

.

How your 2d mesh looks like? are you trying to produce prism elements ?

Is it simple cylinder?

See few pics here attached with post. But keep in mind geometries like these whose axis is passing through them, always give you problems using simple rotation command.

[aerospain]

I get the two first images, but not the last one in Fluent.

I'll be back after trying your previous suggestions.

Thanks!!!

[Far]

enable degenerate option in panel to avoid low quality cells in fluent.

[wyldckat]

Greetings to all!

This is one of those crazy situations that occur due to software itself not being user friendly. Software crashing without giving a decent explanation can be considerably distressing, specially when we're in a hurry.

@aerospain:

Originally Posted by aerospain

I have replied to your private message too, and I can say it publicly as well. I have not used an inappropriate language anywhere, and I would like a second moderator to review the threads. If we are getting too sensitive about things, I feel offended for being pointed at as someone with no manners.

It can be considered that Sijal took pre-emptive measures. The tone on this thread could have easily shifted to the wrong direction, given the posts #4 and #5. As for inappropriate language, it's open to interpretation... keep in mind that with planet Earth housing over 7,000,000,000 people, it's very hard for everyone to interpret a phrase in the same exact way I'm referring to this:

Originally Posted by aerospain

I like to KISS

"Keeping it simple and succinct" or "Keeping it simple and short" is not the first interpretation that most people will read from that acronym: https://en.wikipedia.org/wiki/KISS_principle - and to some people, they will just scratch their head and feel the need to ask: "what does kissing have to do with this?"

And that also doesn't necessarily mean that you don't need provide more details. For example, "Knowledge is power" is a nice expression to say and to keep in mind, but this expression alone is extremely flawed!!


Please allow me to give a bit of perspective from the point of view of someone who is trying to help you:

Originally Posted by aerospain

Someone to post the steps I need to follow for success. (I have watched all youtube videos, and read all tutorials in Help, and I'm missing something)

If you are missing something after following several instructions, then that does not mean that giving you more steps and instructions will help you solve your problem.

Originally Posted by aerospain

It is that I cannot get to a solution because I'm following the wrong steps after creating the axisymmetrical domain to be revolved. So, I'm asking for the steps.

As mentioned in my previous phrase, this is a flawed deduction, because since you didn't tell us what steps you were following, we cannot be certain that even if we give you more "correct" steps, that you will find the missing detail, because the person who writes the new steps may assume that there is an implied step... something that is done by a reflex, like clicking on the "OK" or "Apply" button.

In addition, it would help to know what steps you've followed that were flawed, so that they can be corrected and improved.

Originally Posted by aerospain

Specially yours when no pictures were needed to point me to those links.

Sijal still had to give you additional information - pictures - beyond the links, in order to at least give you a hint in the right direction. Sijal had to predict and deduce what steps you had taken, because you didn't give a perfectly clear picture of what you had already done and tried.


If you had provided more details, instead of "keeping it simple and succinct", it would have been easier to help you in the first place .


Still not convinced? Here's a little story that I can't remember the details from where I got it (a concoction from a few TV shows, probably):

A guy walks into an emergency room, crying out loud that his head hurts and that he needs something for the pain.

A couple of nurses approach him and one says: "please calm down and tell me where it hurts."

He cries back: "my head hurts, I just need something for the pain."

Nurse: Please calm down.

Man: I just need a pill or something. I'm fine. It's just that this pain is killing me.

The nurse tried to touch his arm to try and console him, but the man starts flailing around and saying "I'm fine, I just need a pain killer". The man is suddenly knocked out by an off-duty guard.

So, long story short, MRI showed that the man had - insert painful problem, either a tumour, a bullet, an aneurysm, a broken skull, or a small bar of steel - in his head. A common painkiller pill would not solve the actual problem... it might not even have taken the pain away.

One of the biggest lessons that Computational Fluid Dynamics has taught me so far is:

Assume nothing, test everything! Every single detail, no matter how small, can be more important than we might be willing to believe.

And to always keep in mind that with CFD, we're trying to simulate reality... which is not an easy feat!

Best regards,
Bruno

[aerospain]

disappointed ...

[wyldckat]

Greetings to all once again,

Originally Posted by aerospain

disappointed ...

My apologies for disappointing you and thank you for taking the time to give me some feedback on this.
I did fail to address all issues in the discussion and ironically in my own example (I should have remembered that I'm never at 100% capacity on weekends)... namely that having the off-duty security guard to knock out the man that was already in pain, wasn't the correct approach.

In the instructions given to the moderators includes that we should only intervene when strictly necessary. Sijal has already expressed on the moderators forum that more caution will be taken in future situations. I've retracted the infraction.

@shereez234: Thank you for trying to help, but next time please be more careful in talking/writing to people who are in distress and are seeking help here on the forum.

@Sijal: Thank you for taking the time and patience to help aerospain.

Best regards,
Bruno

[aerospain]

Thanks for the links Sijal,
Still getting an error. Cannot send info about it right now, but will do later on today.
cheers!