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-   -   smoke (fire simulation) (http://www.cfd-online.com/Forums/cfx/23487-smoke-fire-simulation.html)

matt January 5, 2007 05:46

smoke (fire simulation)
 
hi everyone, I am trying to simulate a fire and instead of simulating combustion, i want to release smoke from a surface. However, i could not find physical properties (density, viscosity, etc.) of smoke. does anyone has a suggestion? My main problem is i dont have necessary hardware (such as enough ram) to simulate combustion nor release number of species (CO, CO2, H2O, soot etc.) from a surface. Instead I am trying to find out what would be the viscosity and density of a typical smoke. Instead of releasing 4-5 different species from a surface, i just want to release air and smoke mixture into air. Since it would be impossible to duplicate chemical combination of a car fire, anything close to it would be enough for me. I hope it is clear. thanx much

opaque January 5, 2007 09:54

Re: smoke (fire simulation)
 
Dear Matt,

You can go two ways here:

Alternative 1: Passive scalar -------------

1 - Create an Additional Variable named Smoke

2 - In the domain panel, activate your Additional Variable, and make it a Transport Equation. Do not forget to the the Kinematic Diffusivity so your Smoke can also diffuse into the fluid (Air for example)

3 - Set boundary conditions as you see fit.

4 - Run, and plot.

Alternative 2: Active scalar --------------

1 - Create a new Pure Substance Material named Smoke and set Density, Dynamic Viscosity and Thermal Conductivity as needed.

2 - Create a Variable Composition Mixture Material made of Air and Smoke

3 - In the domain panel, make select a Constrain for your Mixture

4 - Set boundary conditions as needed

5 - Run, and plot..

Do you want to also release heat from the smoke? Then, add a source to the energy equation that is a function of the amount of smoke.

Perhaps, there are other alternatives, but you can improve from here.

Good luck,

Opaque


matt January 5, 2007 10:02

Re: smoke (fire simulation)
 
Thank you so much Opaque for your long response... Appreciated. However, my main problem is to how to calculate the density and viscosity of smoke which may include soot, CO, CO2, H2O...

opaque January 5, 2007 10:12

Re: smoke (fire simulation)
 
Dear Matt,

If you do not want to solve for the components of smoke, you must then come up with a model for smoke itself.

For example, you could say that smoke has certain fixed composition of CO, CO2, H2O, etc.. But, then it is frozen (no more C0->CO2).. That is up to you to model based on your need and characteristics of the fire you have.

Opaque.



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