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WhatIsCGNS.html
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<meta name="GENERATOR" content="Mozilla/4.75 [en] (Windows NT 5.0; U) [Netscape]">
<title>CFD General Notation System</title>
</head>
<body text="#000000" bgcolor="#FFFFFF">
<table BORDER=0 CELLSPACING=5 CELLPADDING=5 WIDTH="100%" >
<tr>
<td WIDTH="180"><a href="http://www.cgns.org/"><img SRC="cgns.gif" ALT="CGNS logo" BORDER=0 height=111 width=180 align=CENTER></a></td>
<td ALIGN=CENTER>
<h1>
<font color="#000000">CFD General Notation System<br>
What is CGNS?</font></h1>
</td>
</tr>
<tr>
<td COLSPAN="2">
<hr></td>
<td> </td>
</tr>
<tr>
<td VALIGN=TOP WIDTH="180">
<table BORDER CELLSPACING=0 CELLPADDING=5 WIDTH="100%" >
<tr>
<td VALIGN=TOP>
<p><b>CGNS site pages</b>
<br><a href="index.html">CGNS Home</a>
<br><b><font color=red>What is CGNS?</font></b>
<br><a href="starting.html">Getting Started</a>
<br><a href="news.html">Latest News</a>
<br><a href="hdf5.html">Switch to HDF5</a>
<br><a href="steering.html">Steering Committee</a>
<br><a href="Implementations.html">Implementations</a>
<br><a href="CGNStalk.html">Discussion Group</a>
<br><a href="download.html">Download</a>
<br><a href="Utilities.html">Contributed Utilities</a>
<br><a href="CGNSFiles.html">Example CGNS Files</a>
<br><a href="Proposals.html">Proposed Extensions</a>
<br><a href="FAQs.html">FAQs</a>
<p><b>Documentation pages</b>
<br><a href="CGNS_docs_current/index.html">Documentation Home</a>
<br><a href="CGNS_docs_current/index.html#Papers">Papers and Slides</a>
<br><a href="CGNS_docs_current/index.html#Minutes">Meeting Minutes</a>
<br><a href="CGNS_docs_current/user/index.html">User's Guide</a>
<br><a href="CGNS_docs_current/overview/index.html">Overview</a>
<br><a href="CGNS_docs_current/sids/index.html">SIDS</a>
<br><a href="CGNS_docs_current/filemap/index.html">SIDS File Mapping</a>
<br><a href="CGNS_docs_current/midlevel/index.html">Mid-Level Library</a>
<br><a href="CGNS_docs_current/cgio/index.html">CGIO User's Guide</a>
</td>
</tr>
</table>
</td>
<td VALIGN=TOP>The CFD General Notation System (CGNS) provides a general,
portable, and extensible standard for the storage and retrieval of
computational fluid dynamics (CFD) analysis data.
It consists of a collection
of conventions, and free and open software implementing those conventions.
It is self-descriptive, machine-independent, well-documented, and administered by
an international steering committee. It is also an American Institute of
Aeronautics and Astronautics (AIAA) <a href="CGNS_docs_current/aiaa.html">
Recommended Practice</a>.
<p>The system consists of two parts: (1) a standard format for recording the data, and
(2) software that reads, writes, and modifies data in that format.
The format is a conceptual entity established by the documentation; the
software is a physical product supplied to enable developers to access
and produce data recorded in that format.
<p>The CGNS system is designed to facilitate the exchange of data between
sites and applications, and to help stabilize the archiving of aerodynamic
data. The data are stored in a compact, binary format and are accessible
through a complete and extensible library of functions. The API (Application
Program Interface) is platform independent and can be easily implemented
in C, C++, Fortran and Fortran90 applications.
<p>How can CGNS help you?
<ul>
<li>It improves the longevity (archival quality) of data
<li>It makes it easier to share data files between sites and collaborators
<li>It is easily extendible to include almost any type of additional data you
can think of
</ul>
<p>The CGNS project originated in 1994 as a joint effort between Boeing
and NASA, and has since grown to include many other contributing organizations
worldwide. In 1999, control of CGNS was completely transferred to a public
forum known as the <a href="steering.html">CGNS Steering Committee</a>.
This Steering Committee is made up of international representatives from
government and private industry.
Additional history on the development of CGNS is available
<a href="CGNS_docs_current/overview/history.html">here</a>.
<p>The principal target of CGNS is data normally associated with compressible
viscous flow (i.e., the Navier-Stokes equations), but the standard is also
applicable to subclasses such as Euler and potential flows.
The CGNS standard includes the following types of data.
<ul>
<li>
Structured, unstructured, and hybrid grids</li>
<li>
Flow solution data, which may be nodal, cell-centered, face-centered, or
edge-centered</li>
<li>
Multizone interface connectivity, both abutting and overset</li>
<li>
Boundary conditions</li>
<li>
Flow equation descriptions, including the equation of state, viscosity
and thermal conductivity models, turbulence models, multi-species chemistry
models, and electromagnetics</li>
<li>
Time-dependent flow, including moving and deforming grids</li>
<li>
Dimensional units and nondimensionalization information</li>
<li>
Reference states</li>
<li>
Convergence history</li>
<li>
Association to CAD geometry definitions</li>
<li>
User-defined data </li>
</ul>
Much of the standard and the software is applicable to computational field
physics in general. Disciplines other than fluid dynamics would need to
augment the data definitions and storage conventions, but the fundamental
database software, which provides platform independence, is not specific
to fluid dynamics.
<hr>
<p><b>All CGNS software is free.</b> The distribution and use of the CGNS software is covered
by the following license:
<p>This software is provided "as-is", without any express or implied warranty.
In no event will the authors be held liable for any damages arising from the use of this software.
<p>Permission is granted to anyone to use this software for any purpose, including
commercial applications, and to alter it and redistribute it freely, subject to the following
restrictions:
<ul>
<li>1. The origin of this software must not be misrepresented; you must not claim that you
wrote the original software. If you use this software in a product, an acknowledgment in the
product documentation would be appreciated but is not required.
<li>2. Altered source versions must be plainly marked as such, and must not be misrepresented as
being the original software.
<li>3. This notice may not be removed or altered from any source distribution.
</ul>
<p>This license is borrowed from the
<a href="http://www.opensource.org/licenses/zlib-license.php">zlib/libpng License</a>,
and supercedes the GNU Lesser
General Public License (LGPL) which previously governed the use and distribution of the software.
<hr>
<p>We encourage anyone to freely use the
<a href="FAQs.html#logoQ">CGNS logo</a> when distributing or documenting CGNS
related information. The logo adds prestige and credibility to web sites, publications,
displays, announcements, and activities. However, the use of the logo in such a way as
to imply approval, endorsement, or responsibility of the CGNS committee is prohibited
without written permission.
</td>
</tr>
</table>
</body>
</html>