CFD Post not calculating gradients

nithinnm123 · January 30, 2020, 12:29

Hi,
I am trying to calculate the gradient of a variable which was defined by an expression. But the value returned is zero across the whole domain.

Here is the expression of the variable:
-6.73979*H2.Mass Fraction-9.76535*H.Mass Fraction-0.84106*O2.Mass Fraction-11.93170*O.Mass Fraction+2.57306*H2o.Mass Fraction-0.40098*Oh.Mass Fraction+0.11357*Ho2.Mass Fraction+24.21178*No.Mass Fraction

Thank You

Opaque · January 30, 2020, 15:57

There are several ways to figure out the problem,

1 - Can you compute the gradient of H2.Mass Fraction?
2 - Does it make sense? i.e. is it what you expect?
3 - Loop over the next term in your original formula and see when it fails.

nithinnm123 · January 31, 2020, 04:26

I don't know why Post can't calculate the gradient. I defined the variable in fluent as a custom field function and then exported the data and used Post to calculate the gradient. This time it worked.

January 30, 2020, 12:29	CFD Post not calculating gradients	#1
nithinnm123 New Member Nithin Join Date: Sep 2019 Posts: 4 Rep Power: 7	Hi, I am trying to calculate the gradient of a variable which was defined by an expression. But the value returned is zero across the whole domain. Here is the expression of the variable: -6.73979H2.Mass Fraction-9.76535H.Mass Fraction-0.84106O2.Mass Fraction-11.93170O.Mass Fraction+2.57306H2o.Mass Fraction-0.40098Oh.Mass Fraction+0.11357Ho2.Mass Fraction+24.21178No.Mass Fraction Thank You

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January 30, 2020, 15:57		#2
Opaque Senior Member Join Date: Jun 2009 Posts: 1,880 Rep Power: 33	There are several ways to figure out the problem, 1 - Can you compute the gradient of H2.Mass Fraction? 2 - Does it make sense? i.e. is it what you expect? 3 - Loop over the next term in your original formula and see when it fails.

January 31, 2020, 04:26		#3
nithinnm123 New Member Nithin Join Date: Sep 2019 Posts: 4 Rep Power: 7	I don't know why Post can't calculate the gradient. I defined the variable in fluent as a custom field function and then exported the data and used Post to calculate the gradient. This time it worked.