(CGNS Documentation Home Page)
(Steering Committee Charter)
(Overview and Entry-Level Document)
(A User's Guide to CGNS)
(Mid-Level Library)
(Standard Interface Data Structures)
(SIDS File Mapping Manual)
(CGIO User's Guide)
(Parallel CGNS User's Guide)
(ADF Implementation)
(HDF5 Implementation)
(Python Implementation)
(CGNS Tools and Utilities)
(Introduction)
(Design Philosophy of Standard Interface Data Structures)
(Conventions)
(Building-Block Structure Definitions)
(Data-Array Structure Definitions)
(Hierarchical Structures)
(Grid Coordinates, Elements, and Flow Solution)
(Multizone Interface Connectivity)
(Boundary Conditions)
(Governing Flow Equations)
(Time-Dependent Flow)
(Miscellaneous Data Structures)
(Conventions for Data-Name Identifiers)
(Structured Two-Zone Flat Plate Example)
Major Differences from Previous CGNS Versions
The following items represent noteworthy alterations and additions to
the SIDS in reverse chronological order. References to CPEX in the following refer to
CGNS Proposals for Extension.
Version 3.4
The following changes were made for Version 3.4.
- Added CPEX 0041 to modify the description of the
Elements_t
structure for MIXED, NGON_n, NFACE_n
element types. Add a new array ElementStartOffset to describe
elements positions and make per process i/o easier.
Version 3.3
The following changes were made for Version 3.3.
- Added CPEX 0039 to define inter-base reference for multi-zone
connectivities, families,
and time dependent pointers to Zones and
Families. A reference to a zone or a family can
now have the pattern {base name}/{zone name} or
{base name}/{family name} in order to refer to
a zone or a family defined in another base.
65 characters are allowed for identifiers in another base.
Base Level Families section added.
New subsection on Multiple Bases added.
Mention of use of 65 characters made in GridConnectivity1to1_t
and GridConnectivity_t.
Added note in UserDefinedData_t.
New maximum character size of 65 in ZonePointers and FamilyPointers in
BaseIterativeData_t.
- Added mention that FamilyName and AdditionalFamilyName
in ZoneSubRegion_t must respect appropriate rules.
- Added ".." to be avoided in names in Data Structure Notation Conventions,
and added mention that entity names cannot exceed 32 characters.
- Added mention that default value for SimulationType is SimulationTypeNull
(in CGNSBase_t).
- Added a note in FlowSolution_t to mention that the NODE element
is not to be used in place of the vertex.
- Added some new subsection headings.
- Fixed typo in section 10.3 (GasModelType_t changed to ModelType_t).
Version 3.2
The following changes were made for Version 3.2.
Version 3.1
The following changes were made for Version 3.1.
- Added a PYRA_13 element in the description of the
unstructured grid element numbering conventions for
pyramid elements.
- Modified the description of the
Elements_t
structure to incorporate the new definition of the
NGON_n element type, and added the NFACE_n
element type.
Also added examples
illustrating their use, including for polyhedral elements.
- Changed Null to xxxxNull and UserDefined to xxxxUserDefined, as appropriate.
- Also made sure that the xxxxNull is listed first, and the
xxxxUserDefined is listed second.
- Added section Model Type Structure Definition.
- Added ZoneSubRegion_t (CPEX 0030).
Made changes associated with CPEX 0031:
(1) added CellDimension to several places in Zone_t,
(2) added new ParentElements and ParentElementsPosition
in Elements_t,
(3) added CellDimension and revamped usage of PointList and PointRange
in FlowSolution_t,
(4) added CellDimension to several places in ZoneBC_t,
(5) added CellDimension and revamped usage of PointList and PointRange
in BC_t,
(6) changes in BCDataSet_t,
(7) added CellDimension and revamped usage of PointList and PointRange
in DiscreteData_t,
(8) changes in FamilyBC_t,
(9) creation of new FamilyBCDataSet_t,
(10) changes in Zone Grid Connectivities, and
(11) addition of ZoneGridConnectivityPointers and ZoneSubRegionPointers
in ZoneIterativeData_t.
A note regarding CPEX 0031: The use of ElementList and ElementRange has been
deprecated in favor of PointList and PointRange, as described in CPEX 0031 and
in relevant sections of this document.
- Added clarity that if rotating about more than one axis, then it is done
in a particular order in
Periodic_t and in
Data-Name Identifiers for Rigid Grid Motion.
- Modified table in
BC_t to include CellCenter GridLocation.
Version 2.5
No changes were made to the data structures for Version 2.5.
Version 2.4
The following changes were made for Version 2.4.
- GridLocation_t,
PointRange, and PointList
have been added to the
BCDataSet_t data structure,
allowing boundary conditions to be specified at locations different
from those used to defined the BC patch.
(E.g., a BC patch may be defined using vertices, with boundary
conditions applied at face centers.)
- Data structures have been added to
FlowEquationSet_t
for describing the electric field, magnetic field, and conductivity
models used for electromagnetic flows.
Corresponding recommended data-name
identifiers have also been added.
- RotatingCoordinates_t
has been added to the Family_t
data structure.
- A BCDataSet_t list
has been added to the FamilyBC_t
data structure, allowing specification of boundary condition data
arrays for CFD families.
- GridLocation_t,
PointRange, PointList,
FamilyName_t,
UserDefinedData_t,
and Ordinal have been
added to the
UserDefinedData_t
data structure.
- The DimensionalUnits_t
and DimensionalExponents_t
structures have been expanded to include units for electric
current, substance amount, and luminous intensity.
- The capability to include rind
data with unstructured grids has been added, and
Rind_t has been added to the
Elements_t structure,
allowing specification of connectivity information for rind
elements.
Version 2.3
The following changes were made for Version 2.3.
Version 2.2, Beta 1
The following changes were made for Version 2.2, Beta 1.
- Axisymmetry_t and
RotatingCoordinates_t
nodes have been added, allowing the recording of data relevant to
axisymmetric flows and rotating coordinates.
- A Gravity_t node has
been added for storage of the gravitational vector.
- A GridConnectivityProperty_t
node has been added, allowing the recording of special properties
associated with particular connectivity patches, such as periodic
interfaces, or interfaces where the data is to be averaged in some
way prior to passing it to a neighboring interface.
- A BCProperty_t
node has been added, allowing the recording of special properties
associated with particular boundary condition patches, such as wall
function or bleed regions.
- Additional flow solution
data-name identifiers are included for variables in rotating
coordinate systems.
Version 2.1, Beta 1
The following changes were made for Version 2.1, Beta 1.
- A node type
UserDefinedData_t
is added for the storage of arbitrary user defined data in
Descriptor_t and DataArray_t children without the
restrictions or implicit meanings imposed on these node types at
other node locations.
- Support for multi-species flows and chemistry has been added.
New gas models have been added to the
GasModelType_t
enumeration, and
ThermalRelaxationModel_t
and ChemicalKineticsModel_t
data structures have been added for describing the thermal
relaxation and chemical kinetics models.
Additional flow solution
data-name identifiers are included.
Version 2.0, Beta 2
The following changes were made for Version 2.0, Beta 2.
Version 2.0, Beta 1
The following changes were made for Version 2.0, Beta 1.
- The capability for recording unstructured zones has been
added to the SIDS.
(These changes occur throughout the document, although some
specific items are listed below.)
- The values UserDefined and Null are now allowed
for all enumeration types (throughout document).
- The following nodes are now defined (some of these also
include additional new children sub-nodes):
Family_t,
Elements_t,
ZoneType_t,
FamilyName_t,
GeometryReference_t,
FamilyBC_t.
- Under CGNSBase_t, the
IndexDimension is no longer recorded; it has been replaced
by CellDimension and PhysicalDimension.
- Under Zone_t, the
optional parameter VertexSizeBoundary has been added for
unstructured zones.
- The method for general connectivity
(GridConnectivity_t)
has been altered.
It now requires the use of either (a) PointListDonor (an
integer, for Abutting1to1 only) or (b) CellListDonor
(an integer) plus InterpolantsDonor (a real).
- The GridLocation_t
structure has been moved up one level
(from BCDataSet_t to
BC_t).
Thus, for example, if the boundary conditions are defined at
vertices (the default), then any associated dataset information
must also be specified at vertices.
- The data-name identifier
LengthReference
has been added (see also the
data-name identifier
conventions for the flowfield solution).
- The νt parameter has
been renamed ViscosityEddyKinematic, and a new parameter
ViscosityEddy, representing
μt, has been defined
(see the data-name identifier
conventions for the flowfield solution).