Physics system

Interaction with Components

The interaction with Components is one of the main goals of the Physics system. Stay tuned for future developments.

Implementing your own Physics

If you have not created the kernels, boundary conditions, and so on, the Physics system is not a good place to start. You must start with a working implementation of your equations before attempting to create a Physics object.

If you do have a working set of kernels, boundary conditions, and other MOOSE objects, that let you solve an equation in MOOSE, you should consider the following before implementing a Physics:

• is user-friendliness a priority for the expansion of my work?

• is the current workflow unsatisfactory in that regard?

• would creating objects programmatically reduce the potential for user-error while allowing sufficient flexibility?

If the answer is yes to all three, then you may start implementing a Physics object for your equation. The simple concepts behind the simulation setup in a Physics is that the add<various MOOSE object> routines are all called on the Physics and they are all called at the same time in the setup as with a regular input file.

So for example, to make a DiffusionPhysics create a finite element diffusion kernel, one can override addFEKernels like this:

void
DiffusionPhysics::addFEKernels()
{
  {
    const std::string kernel_type = "ADDiffusion";
    InputParameters params = getFactory().getValidParams(kernel_type);
    params.set<NonlinearVariableName>("variable") = _temperature_name;  // we saved the name of the variable as a class attribute
    getProblem().addKernel(kernel_type, name() + "_diffusion", params);
  }
}

Notice how we use the PhysicsBase::getFactory() routine to get access to the Factory that will get the parameters we need to fill, and the PhysicsBase::getProblem() to get access to the Problem which stores the objects created.

If you already have an Action defined for your physics, converting it to a Physics should be fairly straightforward. The principal advantages of doing so are:

• benefit from new APIs implemented in the Physics system

• future ability to leverage the Components system to define a complex system

  void checkParamsBothSetOrNotSet(const std::string & param1, const std::string & param2) const;
  template <typename T, typename S>
  void checkVectorParamsSameLength(const std::string & param1, const std::string & param2) const;
  template <typename T>
  void checkVectorParamsNoOverlap(const std::vector<std::string> & param_vec) const;