plasma spraying-vaporization and fume formation

Marcopolopeich · October 27, 2010, 08:04

Hello to everyone.
I am a ragular reader of this forum and this is the first time that I open a topic.
I already searched for a simlar topic with the search function, but I did not find anything suitable. If someone already wrote something complete about it, then the moderators can delete my post.
I would like to simulate vaporization and fume formation in plasma sprayingn processes.
I would like to model the oxidation reaction and the development of the fume plume, including the modeling of buyancy forces.
I am relatively new to this software and to the topic, and I have something like 20 books on my desk.
I would like to know if someone can give me any advice in this topic, especially on the modelling stage.
I already did a few tutorial. Any help that could help me to concentrate my efforts in a reasonable direction are very appreciated. You can also contact me at my email. I would be very happy to discuss with any expert user.
Thank you.
Best regards,
MPP

Marcopolopeich · October 28, 2010, 09:38

The first question I have is:
How would you model the fume formation?
There is a tutorial in which the fume is given as a passive variable, but is this the only approach?
In CFX you can model also some chemical reaction...
From my support I received the answer that both approach are possible, but which approach would be used from an expert user?
I am trying both, but I would appreciate to receive your feedback.
Best regards,
MPP

ghorrocks · October 28, 2010, 18:06

You have a very difficult simulation topic, so expect to do lots of background work before you get anything working. You are going to have to use lots of physics and you should study each physical mechanism individually at first to make sure they are working correctly, then combine them and ensure they are working correctly. This will take a long time and I hope you are not expecting quick answers.

Marcopolopeich · October 29, 2010, 04:24

You`re right.
No, I am not expecting quick answers.
I am studying the physics and as I said, I have plenty of books open on my desk.
Actually I am working alone, and I think that a good discussion with experienced people can bring me some good feedback.
Even though I am not an usual writer of this forum, I know ( I read this forum since at least 2006, my father found some people here always interesting) that there are some topics that are very good developed and discussed, and some topics which are just ignored. I think a lot of people do not understand the sense of this forum and just search for quick answers, but this is not my case.
I think I am just at the start of a long and very hard journey, and I am searching just for some "fellow traveller", who can just walk with me.
This forum can give us the possibility to develop a good discussion and to estabilish a good contact even with people that are far away from my place.
So, why not discuss?
If the discussion goes far beyond the aim of this forum, you can of course warn me.
As I said, I am at the start, and I am seeing the tutorials and I jast saw that some people model the fume as a passive variable. This is an interesting approach. I would like to know what the experienced users of this forum think about this modelling approach.
Best regards,
MPP

ghorrocks · October 29, 2010, 06:59

I am glad you are being realistic about your work.

Why are some posts ignored? Quite simple - people post answers on this forum because they like to help people. It is rewarding to help people who have made an effort and have found an interesting problem. It is boring and pointless to help people who are just looking for shortcuts or have taken on a job which is obviously beyond them.

I wish you luck finding a "fellow traveller", it would be excellent if the forum found somebody like that. But I fear you may be out of luck, your topic is quite specialised and the problems you will face are not ones many people in the forum are aware of let alone interested in.

But to comment on your direct question, passive variables are easy, low CPU load and are unlikely to cause any convergence issues. They are a good first step into modelling this sort of stuff. I highly recommend you play with passive scalars and get a feel for things like diffusivity, rate of convergence, turbulence enhanced diffusivity and all things passive scalars do. Once you have got a good handle on passive scalars you are in a good position to start doing more complicated physics with mass or volume fractions.

October 27, 2010, 08:04	plasma spraying-vaporization and fume formation	#1
Marcopolopeich New Member Hugo Heinz Peich Join Date: Oct 2010 Location: Switzerland Posts: 11 Rep Power: 15	Hello to everyone. I am a ragular reader of this forum and this is the first time that I open a topic. I already searched for a simlar topic with the search function, but I did not find anything suitable. If someone already wrote something complete about it, then the moderators can delete my post. I would like to simulate vaporization and fume formation in plasma sprayingn processes. I would like to model the oxidation reaction and the development of the fume plume, including the modeling of buyancy forces. I am relatively new to this software and to the topic, and I have something like 20 books on my desk. I would like to know if someone can give me any advice in this topic, especially on the modelling stage. I already did a few tutorial. Any help that could help me to concentrate my efforts in a reasonable direction are very appreciated. You can also contact me at my email. I would be very happy to discuss with any expert user. Thank you. Best regards, MPP

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October 28, 2010, 09:38		#2
Marcopolopeich New Member Hugo Heinz Peich Join Date: Oct 2010 Location: Switzerland Posts: 11 Rep Power: 15	The first question I have is: How would you model the fume formation? There is a tutorial in which the fume is given as a passive variable, but is this the only approach? In CFX you can model also some chemical reaction... From my support I received the answer that both approach are possible, but which approach would be used from an expert user? I am trying both, but I would appreciate to receive your feedback. Best regards, MPP

October 28, 2010, 18:06		#3
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	You have a very difficult simulation topic, so expect to do lots of background work before you get anything working. You are going to have to use lots of physics and you should study each physical mechanism individually at first to make sure they are working correctly, then combine them and ensure they are working correctly. This will take a long time and I hope you are not expecting quick answers.

October 29, 2010, 04:24		#4
Marcopolopeich New Member Hugo Heinz Peich Join Date: Oct 2010 Location: Switzerland Posts: 11 Rep Power: 15	You`re right. No, I am not expecting quick answers. I am studying the physics and as I said, I have plenty of books open on my desk. Actually I am working alone, and I think that a good discussion with experienced people can bring me some good feedback. Even though I am not an usual writer of this forum, I know ( I read this forum since at least 2006, my father found some people here always interesting) that there are some topics that are very good developed and discussed, and some topics which are just ignored. I think a lot of people do not understand the sense of this forum and just search for quick answers, but this is not my case. I think I am just at the start of a long and very hard journey, and I am searching just for some "fellow traveller", who can just walk with me. This forum can give us the possibility to develop a good discussion and to estabilish a good contact even with people that are far away from my place. So, why not discuss? If the discussion goes far beyond the aim of this forum, you can of course warn me. As I said, I am at the start, and I am seeing the tutorials and I jast saw that some people model the fume as a passive variable. This is an interesting approach. I would like to know what the experienced users of this forum think about this modelling approach. Best regards, MPP

October 29, 2010, 06:59		#5
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,700 Rep Power: 143	I am glad you are being realistic about your work. Why are some posts ignored? Quite simple - people post answers on this forum because they like to help people. It is rewarding to help people who have made an effort and have found an interesting problem. It is boring and pointless to help people who are just looking for shortcuts or have taken on a job which is obviously beyond them. I wish you luck finding a "fellow traveller", it would be excellent if the forum found somebody like that. But I fear you may be out of luck, your topic is quite specialised and the problems you will face are not ones many people in the forum are aware of let alone interested in. But to comment on your direct question, passive variables are easy, low CPU load and are unlikely to cause any convergence issues. They are a good first step into modelling this sort of stuff. I highly recommend you play with passive scalars and get a feel for things like diffusivity, rate of convergence, turbulence enhanced diffusivity and all things passive scalars do. Once you have got a good handle on passive scalars you are in a good position to start doing more complicated physics with mass or volume fractions.