CFX-Post: uniformly zero gradient of non constant variable
 

Dear all,

I am trying to compute the gradient of a newly created variable. But this gradient is zero every where even though the original variable in not constant.
For example I can obtain the gradient of the static pressure without any problem. But it I create a Mach number variable, its gradient come to be zero everywhere.
I tried a small verification: even when I create a variable var to be var=Static Pressure, the var.Gradient is uniformly zero while Static Pressure.Gradient is not.

Can someone explain me what is going wrong?
And how I can obtain the gradient of newly created variables?

Thanks all and best regards,

ebah