PDF combustion model to simulate reaction of gas i

Mark

Hi,fluent users:

I have three problems about using PDF combustion model to simulate reaction of gas in fluent5.4.

Now in my main fluid region,I define a seperated fluid zone,in which I want to add mass source of only one kind of species.But if I choose PDF combustion model,I can only add source of total mass,momentum,ernergy,turbulence kinetic energy,turbulence dissipation rate,mean mixture fraction and mixture fraction variance.

My problem is that how I can just add mass source of only one kind of species in the seperated fluid zone,just as I can when I choose finite rate model and eddy-dissipation model.

I have another problem.In fluid soure panel, the unit of mean mixture fraction and mixture fraction variance is kg/m^3-s.As my knowlege,There is not unit of mean mixture fraction and mixture fraction variance.

The last problem is about boundary conditions of flow inlet in PDF combustion.In the mannaul,it is said "The fuel or secondary mixture fraction variance can usually be taken as zero at inlet boundaries."In my oxyen stream inlet,I define mean mixture fraction as value zero.Which number I should define mixture fraction variance in my oxyen stream inlet.

All the three problem I spend much too time.Any answer will be welcome. Thank you.

Mark 2001.8.5