Load and boundary conditions

These records specify description of boundary conditions. The general format is following:

*EntType	(num#)(in)
	loadTimeFunction(in) #
	[valType(in) #] [defaultDofs(ia) #]

The order of particular records is optional, boundary condition number is determined by (num#)() parameter. The numbering should start from one and should end at n, where n is the number of records. Time function value (given by loadTimeFunction parameter) is a multiplier, using which each component (value of loading or value of boundary condition) describes its time variation. The optional parameter valType allows to determine the physical meaning of bc value, which is sometimes requared. Supported values are (1 - temperature, 2 - force/traction, 3 - pressure, 4 - humudity, 5 - velocity, 6 - displacement). Another optional parameter defaultDofs is used to determine which dofs the boundary condition should act upon when new nodes are created on the boundaries.

Currently, EntType keyword can be one from

• Dirichlet boundary condition

  BoundaryCondition	prescribedvalue(rn) #
  	[d(rn) #]
  	[isImposedTimeFunction(in) #]

  
  

  Represents boundary condition. Prescribed value is specified using prescribedvalue parameter. The physical meaning of value is fully determined by corresponding DOF. Optionally, the prescribed value can be specified using d parameter. It is inroduced for compatibility reasons. If prescribedvalue is specified, then d is ignored. The nonzero value of isImposedTimeFunction time function indicates that given boundary condition is active, zero value indicates not active boundary condition in given time (the bc does not exist). By default, the boundary condition apply at any time.

• Prescribed gradient boundary condition (Dirichlet type)

  PrescribedGradient	gradient(rm) #
  	[cCoords(ra) #]
  	[isImposedTimeFunction(in) #]

  
  

  Prescribes $v_i = d_{ij}(x_j-\bar{x}_j)$ or $s = d_{1j}(x_j - \bar{x}_j)$ where $v_i$ are primary unknowns, $x_j$ is the coordinate of the node, $\bar x$ is cCoords and $d$ is gradient. The parameter cCoords defaults to zero. This is typical boundary condition in multiscale analysis where $d = \partial_x s$ would a macroscopic gradient at the integration point, i.e. this is a boundary condition for prolongation. It is also convenient to use when one wants to test a arbitrary specimen for shear.

• Nodal fluxes (loads)

  NodalLoad	components(ra) #
  	[cstype(in) #]

  
  

  Concentrated nodal load. The components of nodal load vector are given by components parameter. The size of this vector corresponds to a total number of nodal DOFs, and i-th value corresponds to i-th DOF in associated dof manager. The load can be defined in global coordinate system (cstype = 0) or in entity - specific local coordinate system (cstype = 1, default).

• PrescribedTractionPressureBC

  [isImposedTimeFunction(in) #]

  
  

  Represents pressure boundary condition (of Dirichlet type) due to prescribed tractions. In CBS algorithm formulation the prescribed traction boundary condition leads indirectly to pressure boundary condition in corresponding nodes. This boundary condition implements this pressure bc. The value of bc is determined from applied tractions, that should be specified on element edges/surfaces using suitable boundary loads. The nonzero value of isImposedTimeFunction time function indicates that given boundary condition is active, zero value indicates not active boundary condition in given time (the bc does not exist). By default, the boundary condition apply at any time.