.. _conditions:

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Boundary Conditions and Initial Conditions
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Sierra/SM offers a variety of options for defining boundary and initial conditions. Typically, boundary and initial conditions are defined on some subset of mesh entities (node, element face, element) defining a model. Sierra/SM offers a flexible means to define subsets of mesh entities. :numref:`conditions-mesh` describes commands that will let the user define some subset of a mesh entity using a collection of commands that constitute a set of Boolean operators.

The remaining parts of this chapter discuss the following functionality:

- :numref:`conditions-variable` presents methods for setting the initial values of variables in Sierra/SM. Sierra/SM has the flexibility to set a complex initial state for some variable such as nodal velocity or element stress.

- Kinematic boundary conditions typical of a solid mechanics code (fixed displacement, prescribed acceleration, etc.) are options in Sierra/SM and described in :numref:`conditions-kinematic`. Most of these boundary conditions allow the specification of a time history using a function, a user subroutine, or by reading values from a mesh file.

- :numref:`conditions-velocity` documents many initial velocity options available in Sierra/SM.

- Force boundary conditions typical of a solid mechanics code (prescribed force, traction, etc.) are options in Sierra/SM and described in :numref:`conditions-force`. Most of these force boundary conditions allow the specification of a time history using a function or a user subroutine.

- :numref:`conditions-gravity` discusses the gravity load option. A gravity load is a body force boundary condition.

- :numref:`conditions-centripetal` provides a description of centripetal force boundary conditions can be applied about a prescribed axis.

- :numref:`conditions-prescribetemperature` details many options available for describing a temperature field in Sierra/SM.

- :numref:`conditions-pore` details the options available for describing a pore pressure field.

- :numref:`conditions-fluid` documents how fluid pressure boundary conditions can be applied as a hydrostatic pressure to each node pertaining to a set of prescribed surfaces.

- :numref:`conditions-inertia` documents how the inertia relief boundary condition can be applied to counterbalance the other force boundary conditions on the specified blocks,  surfaces, and/or nodesets.

- :numref:`conditions-specialized` describes many specialized boundary conditions.

.. toctree::
   :hidden:
   :maxdepth: 1

   conditions/general
   conditions/mesh
   conditions/variable
   conditions/kinematic
   conditions/velocity
   conditions/velocityadd
   conditions/force
   conditions/distributed
   conditions/gravity
   conditions/centripetal
   conditions/initialtemperature
   conditions/prescribetemperature
   conditions/pore
   conditions/fluid
   conditions/inertia
   conditions/specialized
