Pedro Quintanilla
Would it be possible to leave the material name whatever and yet assign an auxiliary variable to use a conditional that picks a value for density, conductivity, cp, and viscosity? This would have to be done with UDF, which is not my field. Do you think it would be possible this way?
To explain myself better: I create an Expression named aux with default value 1.
In the UDF code, I import the value of that variable and place a conditional saying if aux==1, rho= T*T+1 (INVENTED EXAMPLE), elseif aux==2, rho=T*T+2.. ..same for conductivity, viscosity and cp.

In this way, for the optimization problem, we could use only the auxiliary variable as input parameter with integer values. Do you think it can work?