Hi,

i do in my topic with premixid combustion some injection of methane in marked cells. with UDM I use DEFINE_SOURCE makro for it. for example, if I need injection 10 g/s in cell, I calculate source

source = (0.001/C_VOLUME(c,t))

but if I do the massbalance and calculate flow rate of methane , it show, that it was more injected as 10 g/s. Does somebady know, what is the correct way for calculate "source"?

Thanks! Vitali

You are probably making your problem more difficult by using define_source. What are the units in your "source" calculation?

Why don't you just use the "boundary condition" panel to go to the region of the fluid you want to set the source in, check source, then enter the mass source. You can use Fluent to get the volume of the region if you don't already have it from before.

If you just want to have a methane source in part of the domain, make sure you define that as a separate fluid region in Gambit.

Good luck.

yes, I use "boudary condition" and I activated "Source Terms" in GUI. Then I can see in the list all species that I use (CH4, O2, CO2 and H20), mass (kg/m3-s), axial momentum and more. After I set my DEFINE_SOURCE in UDF to the methane in the list. I use UDF, because my ijected mass of methan must be change. But my problem is it, I cann't understand, how must I calculate the value of source.

source has units [kg/(m3*s)], so I use formel

source = mass flow of Methan that I inject [kg/s] / C_VOLUME(c,t)[ m3]

But If I calculate in this way, I get to many injected methane. Dose somebody know, what is it wrong? Thanks

Vitali