**pressure

Description

The pressure mechanical boundary condition is used to impose a pressure normal to a surface defined by a liset (in 2D) or a faset (in 3D).

The pressure imposed on a body is applied in the direction of the surface’s normal ^{1 1}You may verify a bset’s normals in Zmaster, and change them with the mesher bset_align.. For instance to model a solid submerged in fluid, the pressure’s value should be negative if the mesh uses the convention of outwards normals, and positive if normals point inwards.

Pressure is calculated on the initial geometry for small deformation/small displacement formulations, and on the updated (deformed) geometry at the start of the increment for small deformation/large displacement formulations. Therefore, in large deformation problems this option may not be appropriate for modeling the fluid pressure on a surface. The **hydro and **hydro_finite_strain commands may be used to apply a pressure on the deformed surface to simulate hydrostatic fluid pressure.

Syntax

**pressure \(~\,~\,\) bset value table … [tableN]

bset

Character name of the line set upon which pressure is applied. The bset can be a liset in 2D problems, and a faset in 3D problems.

value

Base value (real number, function or file) which scales a table value to determine the pressure magnitude.

table

Character name for a valid loading table or tables which will describe the pressure in time.

Example

***bc
  **pressure
    top -20. tab1
  **pressure
    edge 1. time
  ...
***table
  **name tab1
    *time 0. 1. 2.
    *value 0. 1. 0.