some question about diffusion
 

dear Mr.and Mrs.

I am a beginner in fluent.Now,I am solving a fume diffusion which is produced by combustion.The fume is let out from the chimney,I want to knwo the concentration of each species near the ground.But in the course,I met some questions.

I am willing to set the density in the way you taught me,but I can not define the density because there is only "constant" in the tool bar,how can I do?

Second question is how can I set mass diffusion coefficient of mixture material in my question.

Third question:I can not model molecular diffusion or turbulent diffusion.In fact,seeing the solution,I think there it is only affected by advection(fume velocity and air velocity in ambient).The difficult is ,near the ground the concentration of species arezero. How can I do with it.

Hope for your help and thank you very much.

Sincerely

Re: some question about diffusion
 

Hi, the kinetic theory can be used for the set of mass diffusion coefficient of the mixture material.