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 first-level 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 Time Integration Scheme
  3.3.3 Solver Information
  3.3.4 Variables
  3.3.5 Global System Solution Algorithm
  3.3.6 Boundary Regions and Conditions
  3.3.7 Functions
  3.3.8 Quasi-3D approach
 3.4 Filters
  3.4.1 Phase sampling
  3.4.2 Aerodynamic forces
  3.4.3 Benchmark
  3.4.4 Cell history points
  3.4.5 Checkpoint cell model
  3.4.6 Checkpoint fields
  3.4.7 Electrogram
  3.4.8 Error
  3.4.9 FieldConvert checkpoints
  3.4.10 History points
  3.4.11 Kinetic energy and enstrophy
  3.4.12 Mean values
  3.4.13 Modal energy
  3.4.14 Moving body
  3.4.15 Moving average of fields
  3.4.16 One-dimensional energy
  3.4.17 Reynolds stresses
  3.4.18 Time-averaged fields
  3.4.19 ThresholdMax
  3.4.20 ThresholdMin value
  3.4.21 Maximun/minimun fields
 3.5 Forcing
  3.5.1 Absorption
  3.5.2 Body
  3.5.3 MovingReferenceFrame
  3.5.4 Programmatic
  3.5.5 Noise
 3.6 Coupling
  3.6.1 File
  3.6.2 Cwipi
 3.7 Expressions
  3.7.1 Variables and coordinate systems
  3.7.2 Performance considerations