General Structure

General structure in terms of main top-level classes is shown in Fig (fig-generalstructure). The key class is EngineeringModel representing the problem under consideration. It can contain one or more domains (abstractions for computational mesh) represented by the Domain class. This class contains the domain description, or if the program runs in parallel, then it contains the description of the domain associated with a particular processor or thread of execution. Domain class contains and manages lists of dof managers (such as nodes), elements, boundary conditions, cross sections, and material models - these describe the geometry of the problem, its constitutive properties, and applied boundary conditions. Services for accessing each of these objects are provided. Domain class & object provides services for reading input files and instantiating corresponding components accordingly.

OOFEM Top level structure

The EngngModel class is an abstraction for the problem under consideration. It represents the type of analysis to be performed. Base class declares and implements the basic, general-purpose services for assembling characteristic components of governing equations and services for starting the solution step and its termination. Derived classes know the form of governing equation(s) and the physical meaning of individual terms forming governing equation(s). The derived classes, representing specific problem, are responsible for forming the governing equation(s) for each solution step, usually by summing up the contributions from individual elements and nodes. The underlying discrete problem is subsequently solved by suitable instance of NumericalMethod class, that can take advantage of efficient sparse store for characteristic matrices, represented here by SparseMtrx class. This part is described in detail in `ProblemFrame`_.

Class Element, is an abstraction of a finite element. Element manages its DofManagers (nodes), and has its cros section and material models defined by CrossSection and Material class instances. Element manages its Integration rules composed of individual integration points and can also have its internal DOFs.

DOF class is an abstraction for a single degree of freedom (DOF). It maintains its physical meaning and associated equation number. DOF is the attribute of DofManager class, which manages the collection of DOFs. A typical derived class is class Node, representing a node in a finite element mesh.

BoundaryCondition and InitialCondition classes are abstractions of boundary and initial conditions. They are attributes of Domain class and are associated with one or more DOFs. The abstract class Load, derived from parent BoundaryCondition class, is an abstraction for load. It is an attribute of Domain and can be associated with several dof managers or elements, according to the type of loading it represents. The class declares the basic services provided by all derived classes. Derived classes declare specific load type dependent services and implement all necessary services.