Sensitivity Problem Formulation

Because the Sensitivity interface does not contain any physics, it is not intended for use on its own. When the physics interface is added to a multiphysics model, no new equations are introduced, and the set of solution variables remains the same. Instead, an objective function and a set of control variables can be specified. The Sensitivity interface can perform these distinct tasks:

•	Select control variables and set their values

•	Define scalar objective functions

The control variables are independent variables whose values are not affected by the solution process, but they are also degrees of freedom (DOFs) stored in the solution vector. When defining a control variable, its initial value must be supplied. The initial value is used to initialize the control variable DOFs, which remain fixed during the solution step.

The companion Sensitivity study step is responsible for:

•	Choosing which objective functions and control variables to solve for

•	Selecting a sensitivity evaluation method

•	Selecting which study step to compute sensitivities for

•	Setting up the Sensitivity solver extension