Elementary Boundary Conditions

Material LAW11 is used to specify the elementary variables at the boundary of the computational domain.
  • Option 0 specifies stagnation conditions for perfect gas (Bernoulli inlet).
  • Option 1 specifies stagnation conditions for a linear compressible material (Bernoulli inlet).
  • Option 2 imposes values (inlet/outlet).
  • Option 3 is for non-reflective frontiers (outlet).
For example, in the input deck, density and energy are imposed constant at the inlet. Non-reflective frontiers are imposed at the outlet. Then, the flux is injected at inlet through imposed velocities at nodal points.

Non-Reflective Frontiers (NRF)

Option 3 of Material LAW11 is used to prevent outgoing wave reflections on the boundaries of the domain.

Two possibilities are:
  • An average pressure is imposed via a function. A relaxation term is added to let the average pressure converge toward the imposed value. This is well suited for outlets.
  • An average pressure is calculated from the neighboring element pressure and the pressure converges toward this always changing value.

The impedance of the boundary is exactly the wave impedance of a monopole radiating at distance 2lc from the boundary, where lc is specified in the input data for this law.

This non-reflective frontiers (NRF) is not effective when velocities are imposed or when nodes are fixed.