[ofer]

Hello,
I am trying to understand how this fire combustion expression works:

if(x<20[m]*0.04689*t^2/20000[s^2],0.02 [kg m^-3 s^-1],0 [kg m^-3 s^-1])

So far i only understood that
alpha*t^2=Q is the fire growth rate, (not sure why we divide by Q?)
And that 0.02 is mass burn rate over a fire domain of 20mX2mX0.5m.
How does the if condition works?

Thanks

[ghorrocks]

In english, the expression says:

If node x location is less than 20 metres*0.04689*time (in seconds)^2/20000[seconds^2] (so a quadratic in time in x direction), then return 0.02 kg/m^3 per second (so that sounds like some mass per unit volume being generated), otherwise do nothing.

Read the CFX reference guide for more details on the if statement.