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Pressure loads are applied to the surface of the geometry and are defined by the surface_load element with the type attribute set to pressure. These pressure forces are also known as follower forces; they change direction as the body is deformed and, in this case, are always oriented along the local surface normal. The sign convention is so that a positive pressure will act opposite to the normal, so it will compress the material. The surface that the load is applied to is specified with the surface attribute.The surface must be defined in the Mesh section.
 parameter Description default pressure The applied pressure values (1) 0 [P] symmetric_stiffness symmetric stiffness flag (2) 1 linear linear flag (3) 0 shell_bottom shell bottom flag (4) 0
<surface_load type="pressure" surface="surface1">