Name

dof_init and dofdot_init — dof (solution) fields block

Synopsis

dof_init | dofdot_init id
  value v dof list nodes...
end

Description

dof_init and dofdot_init allow for defining initial DOF fields (such as displacements or temperatures) or initial time derivative of DOF's fields (such as velocities) on the database. A dof_init or dofdot_init set is identified by id, a non-negative integer which must be unique for the initial conditions of the current model. id is the number which is referenced by the dof_init and dofdot_init options of the case definition. Sets with an id of 0 will be active for all analysis cases.

Specifying Values and Degrees-of-Freedom

The directive value is used to specify the magnitude. This value is assigned to one or several degrees-of-freedom by means of the directive dof. The couple (value, degrees-of-freedom is then assigned to individual nodes or collections of nodes.

The directive value v takes a single floating-point number, for example:

value 0

The directive dof is followed by a list which identifies the degrees-of-freedom, for example:

value 2 dof [UX UY]
  • In stress analysis, UX, UY, and UZ represent the displacement in the x-, y-, and z-direction, respectively.

  • In stress analysis, RX, RY, and RZ represent the rotation (in radians) about the x-, y-, and z-axes, respectively.

  • In heat analysis, T means the temperature.

  • When a single degree-of-freedom is locked or set rather than a list of degrees-of-freedom, the square brackets can be omitted:

    value 5 dof UZ
  • The degrees-of-freedom that are present at a given node depend on the elements to which this node is connected. Specifying a value for a degree-of-freedom that does not exist will have no effect.

The following directives are available to assign initial conditions to individual nodes and to collections of nodes:

allnodes

Assign the initial conditions to all defined nodes of the current branch.

branch br

For models that consist of several branches. Specifies the external branch number br. To be used in conjunction with the allnodes and nodes directives.

epatch id p1-p8|e1-e12|f1-f6|b

When the discretization of a part of the discretization was created by means of the epatch command, a number of pre-defined nodelists are available for use with the ebc command. The epatch is identified by id.

Individual patch vertex nodes are specified with p1 to p8.

The collection of nodes that are located at a patch edge are specified with e1 to e12.

The collection of nodes that are located at a patch face are specified with f1 to f6.

The collection of nodes of the whole patch body are specified with b.

nodes list

Specifies a list of nodes (of the current branch) to which the initial conditions will be assigned.

nodelist name

Specifies the name of the node list to which the initial conditions will be assigned.

nodeset name

Specifies the name of the node set to which the initial conditions will be assigned.

Examples

Create an initial dofdot (velocity field) which os uniform, with a velocity of 5 in z-direction. Note that all other dof's are implicitly set to 0.

dofdot_init 123
  value 5  dof UZ  allnodes
end

The field must be activated in the case definition. Example: Assign the initial velocity field to case 1.

case 1
  ...
  dofdot_init 123
  ...
end