def BuildMeshBoundaryForFluids(self):
# set building options:
mesh_id = 0
# define building utility
model_part_name = self.settings["model_part_name"].GetString()
skin_build = KratosPfemBase.BuildModelPartBoundary(
self.main_model_part, model_part_name, self.echo_level)
# execute building:
skin_build.Execute()