Gravity models

The gravity model is responsible for describing the magnitude and direction of the gravity vector at each point inside the domain. To implement a new gravity model, you need to overload the aspect::GravityModel::Interface class and use the ASPECT_REGISTER_GRAVITY_MODEL macro to register your new class. The implementation of the new class should be in namespace aspect::GravityModel.

Specifically, your new class needs to implement the following basic interface:

template <int dim>
    class aspect::GravityModel::Interface
    {
      public:
        virtual
        Tensor<1,dim>
        gravity_vector (const Point<dim> &position) const = 0;

        virtual
        void
        update ();

        static
        void
        declare_parameters (ParameterHandler &prm);

        virtual
        void
        parse_parameters (ParameterHandler &prm);
    };

The kind of information these functions need to provide is discussed in the documentation of this interface class at aspect::GravityModel::Interface. The first needs to return a gravity vector at a given position, whereas the second is called at the beginning of each time step, for example to allow a model to update itself based on the current time or the solution of the previous time step. The purpose of the last two functions has been discussed in the general overview of plugins above.