Learning Forum

[adi959719]

Hi,

I'm running a transient simulation with some user defined scalars. One of the uds is space charge and have the unit Coulombs/kg (C/kg). The UDS is implemented using the default unsteady function and mass flux as the flux function. 

On a wall, I want to set zero flux boundary condition on the space charge uds initially. However, after a flowtime of more than 1 second. I want the wall to act as a sink that depletes that uds at a rate of 0.1 C/(m^2.s).

I would like to know if the following method correct: 

1. Set the bc of the wall as "specified flux" and set the value as an expression. The expression is "if(t>1[s], 0.1, 0)"

I don't think it is right, cause the expression always yield to 0, how do I implement this?

 

 

 

  

[NickFL]

Do you mean with your named expressions? Then I believe the if must be IF to be valid, i.e. upper-case.

[adi959719]

Oh yes i meant to put upper-case IF....but is the flow-time just accessed using the expression t?

[Federico]

Correct, the variable t is the way to access flow time in your expression