Nodal Boundary Conditions

By default, kinematic constraints act on material velocities and accelerations. In Radioss, you can define a wide variety of such constraints. For multi-physic and fluid applications, options are:
  • Fixed and full slip boundary conditions
  • Imposed velocities (imposed flux at inlet)
  • Rigid links (temporary adds during restarts)
  • Rigid bodies to model rigid structures and connections and also to compute drag and lift forces (fluid impulse on rigid body is stored in time history database)
Grid constraints act only on grid velocities. Specify:
  • Fixed and full slip grid conditions
  • Lagrangian conditions (grid and material velocity are equally set)
  • ALE links to maintain regular distribution of nodes
  • Imposed grid velocities (moving inlet and outlet)
If fixed node with /BCS, then it means grid and material are fixed. If /ALE/BCS is used, then it is different. First 3 codes defined grid DOF, the second 3 codes defined if node act like Lagrangian in the corresponded direction.

Figure 1.


If set Grilag=010 000, it means just fix grid in Y direction, material could move in Y direction.

If set Grilag=000 010, it means nodes are like Lagrangian in Y direction, gird and material are tied on these nodes in Y direction.

If set Grilag=010 010, it means gird and material are tied on these nodes in Y direction and fixed in Y direction. It is like trarot=010 000 in /BCS.

Figure 2.