CFD Online Logo CFD Online URL
Home > Forums > FLUENT

Having problems setting up boundary conditions for paint chamber simulation

Register Blogs Members List Search Today's Posts Mark Forums Read

LinkBack Thread Tools Display Modes
Old   December 3, 2014, 11:26
Default Having problems setting up boundary conditions for paint chamber simulation
New Member
Jon Tao
Join Date: Dec 2014
Posts: 1
Rep Power: 0
shigua is on a distinguished road
Sponsored Links
Hi everyone and thanks for you help.

I'm working on a project where I have to simulate a spray paint chamber and model the flow velocity and VOC concentration from paint within the chamber. The chamber is essentially a rectangular box with the ends and roof open to air with exhaust fans that suck the air in the chamber out the bottom. The fans are in the ground against the walls along the length of the chamber. The only inflow in the chamber is the spray gun (centered in the chamber), which is spraying a mixture of air and VOC. I specified the VOC as toluene for now. The simulation is set to steady and all fluids are incompressible ideal gases.

The spray speed is specified as well as the mass flow of the VOC, so I have set the spray gun as an inlet velocity for the boundary condition with positive velocity (with the correct mass fraction of VOC). The air going into the fans is also specified so I set those as inlet velocities as well, with negative velocities since the air is leaving the chamber.

The roof and ends of the chamber are set as outflow as the velocity is not specified.

When I run the simulation, the velocity profile looks exactly what I would expect, with high velocity coming out of the spray gun and into the fans and with lower velocities coming in from the roof and ends. But when I look at the concentration, it is the exact opposite of what I would expect. The concentration of the VOC coming out of the spray gun is very low (<1 mass%) and the spray gun is the only source of VOC. When I look at the concentration profile, it looks like the entire chamber is filled with VOC rather than air. I'm thinking that it's because since the roof and ends are set as outflow, but it doesn't know that it should only be taking in 100% air and I don't know how to set that condition.

I have tried setting the roof and ends to inlet vent (against the project specifications) so I could set the concentration to 100% air, but I don't know what the gauge pressure should be and setting pressure to 0 results in an incorrect (or nonexistent) velocity profile.

Please help! Thank you!
shigua is offline   Reply With Quote
Sponsored Links


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On

Similar Threads
Thread Thread Starter Forum Replies Last Post
Domain Imbalance HMR CFX 5 October 10, 2016 05:57
ribbed channel / simpleFoam / boundary conditions beeo OpenFOAM Pre-Processing 20 July 17, 2013 08:39
Boundary conditions for 2D Navie-Stockes simulation L1011 OpenFOAM 5 December 13, 2012 09:17
Setting Pressure outlet boundary for simulation of Radial impeller Mukund Pondkule Main CFD Forum 1 April 5, 2011 09:24
A problem about setting boundary conditions lyang Main CFD Forum 0 September 19, 1999 18:29

Sponsored Links

All times are GMT -4. The time now is 19:52.