Chapter 3
XML Session File

The Nektar++ native file format is compliant with XML version 1.0. The root element is NEKTAR which contains a number of other elements which describe configuration for different aspects of the simulation. The required elements are shown below:

1<NEKTAR> 
2  <GEOMETRY> 
3    ... 
4  </GEOMETRY> 
5  <EXPANSIONS> 
6    ... 
7  </EXPANSIONS> 
8  <CONDITIONS> 
9    ... 
10  </CONDITIONS> 
11  ... 
12</NEKTAR>

The different sub-elements can be split across multiple files, however each file must have a top-level NEKTAR tag. For example, one might store the geometry information separate from the remaining configuration in two separate files as illustrated below:

geometry.xml

1<NEKTAR> 
2  <GEOMETRY> 
3    ... 
4  </GEOMETRY> 
5</NEKTAR>

conditions.xml

1<NEKTAR> 
2  <CONDITIONS> 
3    ... 
4  </CONDITIONS> 
5  <EXPANSIONS> 
6    ... 
7  </EXPANSIONS> 
8  ... 
9</NEKTAR>

Note: When specifying multiple files, repeated XML sub-elements are not merged. The sub-elements from files appearing later in the list will, in general, override those elements from earlier files.

For example, the NekMesh utility will produce a default EXPANSIONS element and blank CONDITIONS element. Specifying a custom-written XML file containing these sections after the file produced by NekMesh will override these defaults.

The exception to this rule is when an empty XML sub-element would override a non-empty XML sub-element. In this case the empty XML sub-element will be ignored. If the custom-written XML file containing CONDITIONS were specified before the file produced by NEKMESH, the empty CONDITIONS tag in the latter file would be ignored.

 3.1 Geometry
  3.1.1 Vertices
  3.1.2 Edges
  3.1.3 Faces
  3.1.4 Element
  3.1.5 Curved Edges and Faces
  3.1.6 Composites
  3.1.7 Domain
 3.2 Expansions
 3.3 Conditions
  3.3.1 Parameters
  3.3.2 Solver Information
  3.3.3 Variables
  3.3.4 Global System Solution Information
  3.3.5 Boundary Regions and Conditions
  3.3.6 Functions
  3.3.7 Quasi-3D approach
 3.4 Filters
  3.4.1 Time-averaged fields
  3.4.2 Moving average of fields
  3.4.3 Reynolds stresses
  3.4.4 Checkpoint fields
  3.4.5 History points
  3.4.6 ThresholdMax
  3.4.7 ThresholdMin value
  3.4.8 One-dimensional energy
  3.4.9 Modal energy
  3.4.10 Aerodynamic forces
  3.4.11 Kinetic energy and enstrophy
 3.5 Forcing
  3.5.1 Absorption
  3.5.2 Body
  3.5.3 Programmatic
  3.5.4 Noise
 3.6 Analytic Expressions
  3.6.1 Variables and coordinate systems
  3.6.2 Performance considerations