Prescribed_boundary_data
Contents
Data Structure: Prescribed_boundary_data |
|
Description |
Boundary surface definition data |
Usage |
Prescribed_boundary_data NUM=ival where ival is the data structure number |
Description |
Overview The Prescribed_boundary_data structure is used to define a special prescribed displacement boundary condition where either: Lagrangian Description The geometry of the model is prescribed to be located on a rigid boundary surface; e.g. the basement geometry. The advantage of this load type is that the rigid boundary surface may be assigned a prescribed movement corresponding to the evolution of the sediment independent of the model geometry; e.g. differential uplift, fault offset, etc. This type of differential displacement would be difficult to apply directly to the model due to the changing mesh topology; e.g. continuous remeshing that is used to accommodate the large deformations. The facets of the part geometry remain unchanged, however, by remeshing operations.
Eulerian Description The material is free to move relative to the boundary surface and material is continuously added or removed from the model, so the model domain is consistent with the boundary surface geometry. This option is used for example to define sedimentation or erosion processes in a geomechanical analysis.
The prescribed boundary loading is defined by: •Defining the rigid boundary surface using the boundary surfaces data structures (see Part_geometry_set ). •Assigning the rigid boundary to specific geometry entities using the Boundary_surface_data data structure. The entities may be defined as a list of lines (2-D) or surfaces (3-D) or by a sediment horizon. •Defining a boundary movement (if required) via the Part_geometry_update and Boundary_surface_update data structures (in conjunction with a Time_curve to define the displacement rate).
Notes •One Prescribed_boundary_data structure is defined for each boundary surfaces set. •When a Lagrangian prescribed boundary is assigned to geometry lines (2-D) or surfaces (3-D) these entities should not be prescribed support conditions using Support_data or Prescribed displacement loading via Global_loads.
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 | Name Name of the prescribed boundary set |
| Sediment_horizon Name of sediment horizon to be assigned to the boundary |
| Part_geometry_set Name of part geometry to be assigned to the boundary |
| Geometry_set Name of the geometry set to be assigned to the boundary |
| Lines List of lines on the boundary surface |
| Surfaces List of surfaces defining the boundary surface |
| Time_curve Time curve name or number |
| Boundary_type Type of boundary surface (Lagrangian or Eulerian) |
| Lagrangian_algorithm Type of Lagrangian boundary surface |
| Eulerian_update_frequency Update frequency for Eulerian boundary check |
| Eulerian_automatic_update Automatic frequency Eulerian update flag |
| Eulerian_displacement_factor Displacement factor for Eulerian boundary nodes |
| Eulerian_algorithm Type of nodal update for Eulerian Deposition/Erosion |
| Sedimentation_flag Defines that the added material for Eulerian boundary is due to sedimentation |
| Sedimentation_porosity Porosity of material added to the model for Eulerian boundary |
| Eulerian_output_frequency Frequency for output of Eulerian update information to log file |
| Search_tolerance Search tolerance for normal distance check for Eulerian boundary |
| Reference_coordinates Reference coordinates for move to surface type "Preserve_length" |
| Edge_element_fixity_flags List of edge element fixity flags |
| Search_type Defines the search algorithm for identifying nodes on the part boundary |