Object-oriented methods are becoming more and more important in order to meet the challenges in scientific computing, such as the treatment of coupled multi-field problems with high spatial resolution. This paper introduces an object-oriented concept for modelling multi-process systems in porous media. The basic idea is the direct representation of a physical process by an object of the numerical code.

Because a physical process can be represented by a field variable and an equation system, the process object contains the equation system for the field variable as well as all methods needed for building and solving the equation system. The process object is thus self-configuring and well encapsulated, which are the main advantages of this new approach and thus allows for an easy extension to more complex applications with a higher number of processes.

The design and implementation of the object-oriented concept for the presented process objects is described in detail and illustrated by a set of application examples.