Understanding design variables

A design variable is a simulation entity of your model that the TMG Correlation solver varies within a specific range during the optimization to reduce the gap between the reference data and the simulation results.

You can apply design variables on:

• Boundary condition parameters, which are usually the magnitude of a load, constraint, or simulation object, such as the heat transfer coefficient in the Thermal Coupling simulation object, or the heat pickup in a Thermal Stream load.
• Expressions used in any boundary condition, such as HTCFORCE(34[mm],"DUCT_FULL"), which models convective heat transfer between the fluid in a duct network and the walls of the duct, using standard correlations for forced convection in a 1D flow system with a fully developed boundary layer.

TMG Correlation lets you apply design variables as a:

• Substitution—replaces the selected parameter or expression with a new expression that is the design variable. The design variable has the units of the original parameter or expression.
• Multiplier—adds in front of the selected parameter or expression, a multiplier that is the design variable. The design variable is unitless. The same multiplier design variable can be applied to multiple parameters or expressions.