Smoke

njssdfu · September 10, 2010, 15:36

Hello,
I would like to try simulate smoke spreading across room. But I'm lost in settings. Could you show me an example?
I have a room, doors are inlet and outlet is through window or opening in roof. Smoke is created from burning the wood or something.
I was doing only structural analysis, so I really don't know where to start.
Thank you for help.

ghorrocks · September 11, 2010, 06:08

The simplest approach is to use an additional variable. This adds very little additional computational load and should have no convergence problems but is only valid if the smoke does not affect the material properties of the fluid. If you are new to CFD then start with this option anyway to get the hang of it. By material properties I don't mean temperature - you can still model buoyancy with an additional variable. I think there are some tutorial examples which use additional variables as tracers like this.

If the material properties of the smoke do affect the material properties then you have to consider things like multi-component gases. An example of this is the slumping CO2 tutorial which comes with CFX. This type of modelling will add significant additional computational load and be harder to converge but has the ability to model the varying material properties of the smoke/air mixture. For this approach to be worthwhile then you need to know the composition and material properties of your smoke. If you don't know this then forget this approach and just use the simpler additional approach.

September 10, 2010, 15:36	Smoke	#1
njssdfu New Member Tom Join Date: Sep 2010 Posts: 4 Rep Power: 15	Hello, I would like to try simulate smoke spreading across room. But I'm lost in settings. Could you show me an example? I have a room, doors are inlet and outlet is through window or opening in roof. Smoke is created from burning the wood or something. I was doing only structural analysis, so I really don't know where to start. Thank you for help.

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September 11, 2010, 06:08		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	The simplest approach is to use an additional variable. This adds very little additional computational load and should have no convergence problems but is only valid if the smoke does not affect the material properties of the fluid. If you are new to CFD then start with this option anyway to get the hang of it. By material properties I don't mean temperature - you can still model buoyancy with an additional variable. I think there are some tutorial examples which use additional variables as tracers like this. If the material properties of the smoke do affect the material properties then you have to consider things like multi-component gases. An example of this is the slumping CO2 tutorial which comes with CFX. This type of modelling will add significant additional computational load and be harder to converge but has the ability to model the varying material properties of the smoke/air mixture. For this approach to be worthwhile then you need to know the composition and material properties of your smoke. If you don't know this then forget this approach and just use the simpler additional approach.