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Understand a CEL expression

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Old   February 26, 2018, 16:11
Default Understand a CEL expression
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ofer d
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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
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Old   February 26, 2018, 16:45
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Glenn Horrocks
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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.
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