**process surface_normals

Description

This post processor computes the outer-pointing normals at nodes in the specified nset, and generates associated nodal fields. It currently works in 3D only.

Defining a normal direction at a node on a ridge is naturally ambiguous. Each node receives a contribution of its attached elements, if all nodes of the elements are in the specified nset. Thus, on ridges the normal is averaged over adjacent elements. Restricting the computation to a smooth subset of the surface will usually generate the desired field.

Syntax

**surface_normals [ *prefix prefix ]

prefix is used to name the output variable. Its default value is N so that normal vector components are N1, N2 and N3.

Example

% This post processing calculates outer-pointing
% heat flux from a thermal calculation
****post_processing
 ***global_post_processing
  **file node
  **nset interior
  **process surface_normals
   *prefix N
    % Can be visualized in paraview with this calculator:
    % N1*iHat+N2*jHat+N3*kHat

 ***local_post_processing
  **file node
  **nset interior
  **process function
   *expression q1*N1 + q2*N2 + q3*N3 ;
   *output normalflux
****return