# 4.10.9. Fixed

The fixed boundary condition sets a dirichlet for specified values and is not commonly used in Fuego except for cases where pressure is ill-defined and needs to be fixed somewhere. In that case, a fixed boundary condition can be used on a single-node nodeset to set the pressure (e.g. in a case where your domain has no specified pressure boundaries and is not acoustically compressible, such as where you have all wall and mass flux boundaries).

    begin fixed boundary condition on surface nodeset_1
      pressure = 0.0
    end

Note

Fuego will detect if the pressure is not fixed anywhere and automatically add a fixed boundary condition on a single node in the domain. If you want to control which node this is set on, you can define a nodeset and set the boundary condition manually.

The complete list of available commands for the fixed boundary condition and the syntax for the different options can be found in Fixed Boundary Condition On Surface.