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Frequently Asked Questions

What is the QNET Wiki?

The Qnet Wiki Knowledge Base is the world's foremost repository of structured knowledge and advice designed to underpin quality and trust in the industrial application of CFD. The QNET Wiki is intended to share the best practice in CFD modelling for all industrial applications. ERCOFTAC members are permitted to access authoritative advice for using state of the art turbulence models for their engineering or physics problems. Click on the following link for more information regarding the QNET-CFD Network.

What does the Wiki contain?

The knowledge base is partitioned into Gold and Silver Domains and are application centred, facilitating the identification of appropriate knowledge and advice for specific industrial purposes. They are organised around;

  1. Application Areas
    • Each Application Area is comprised of Application Challenges (AC) which are realistic industrial test cases used to judge the competency and limitations of CFD for a given Application Area.
  1. Underlying Flow Regimes

The knowledge base is partitioned into Gold and Silver Domains. The Gold Domain is the repository for content that has been carefully checked and therefore satisfies high quality standards. The Gold Domain is restricted to ERCOFTAC members who will be issued with privileged access. However, the list of all Application (AC) Challenges and Underlying Flow Regimes (UFR), (both described below) with their abstracts are in the public domain.

The Silver Domain is the repository for less mature content which is still under discussion and open for improvement. Parts of the Silver Domain are marked as Silver . This is reserved for content which has matured to levels of quality and significance approaching Gold standard, and made public to serve as examples of the high quality found in the Gold domain. In some cases it will act to invite the addition of new CFD results obtained with alternative models. Both Silver and Silver are fully in the public domain.

The QNET Wiki contains articles on Application Areas and Underlying Flow Regimes. The first case presents the user with a number of categories of applications of interest to an engineer who is analysing a current product or design. Underlying flow regimes present different categories of flow types and flow physics that engineers can use to understand their individual flow analysis problems.

Content is of three types:

  • Gold content- high quality articles that have passed quality reviews by the ERCOFTAC editorial board. Access is only permitted to ERCOFTAC members.
  • Silver Plus content- Silver Plus (or Silver+) articles have been quality reviewed to Gold standard but which are offered as 'free samples' to the public.
  • Silver content- good quality, but not to the same standard as Gold or Silver Plus articles. Freely accessible to the public. The Gold Domain is the repository for content that has been carefully checked and therefore satisfies high quality standards. The Silver Domain is the repository for less mature content which is still under discussion and open for improvement.

What does each article contain?

Each article contains the following group of pages:

  • A brief abstract of what the test case article contains
  • A detailed description of the problem addressed
  • A description of the test data used
  • The results of the CFD calculations for this case
  • Best Practice advice for this type of case
  • A quality evaluation report

Who can access the QNET Wiki?

ERCOFTAC Members are permitted to see all of the articles including Gold, Silver+ and Silver standard content. They are allowed to leave comments on each article in the 'discussion' tab for each page.

The public are permitted to see the abstracts for Gold articles and all of the pages for the Silver+ and Silver articles. They can also leave comments on the pages in the discussion tab.

What software is used for this wiki?

This web site uses the MediaWiki wiki framework [1]. Wikipedia fans will notice the similar appearance to Wikipedia: this is because MediaWiki powers both (look for the little image in the bottom right hand side of each page...).

What content can I add?

Authors of new content can upload text, images and are provided facilities for editing equations. You can also insert links to other web sites and file repositories.

All content and submissions have to be in latex format. If you wish to submit a word document you will have to convert your word document first, by using a HTML converter, into the desired MediaWiki Text. Once this has been achieved a simple copy and paste is all that is required. To do this firstly load the word doc file into OpenOffice and save it as a HTML file. Next, load the HTML file into a browser and paste the HTML into the web-based converter found here. Select the correct wiki format which must be MediaWiki Text and press the button. Then simply paste the converter output into the wiki editor when making your contribution and clean up by hand.

To insert equations you will need to use LaTex. Examples of how to contribute equations can be found here. Look for more information at the MediaWiki web site if you plan to use equations.

At present data files can only be uploaded by special arrangement with the site administrators. This is still being worked on and we hope to have an improved mechanism for uploading these files soon.

How do I contribute a new article or modify an existing article?

The procedure for entering new content into the Wiki is described here.


All sections of the Knowledge Base can be accessed by clicking on the left hand navigational drop down menu. By pointing the cursor at the links, a roll out drop down menu will appear where further pages relating to the chosen topic will be displayed. If a drop down menu does not appear, simply click on the link and you will go directly to that page.

The content of each AC and UFR test case article are presented in the top navigational strip. Simply click on each tab heading to view and move between the various documents. Note that the heading turns "yellow" once selected.

You will also find the exact same navigational strip at the bottom of each AC and UFR test case article to prevent having to keep scrolling up the page to go to the next document in the particular AC or UFR.

We plan to improve the navigation features over time.

The Navigation Tree is not correctly rendered!

There may be difficulties with your browser if this happens. Check the Javascript policy on your browser or download the latest version of Internet Explorer or Firefox to see if this helps.

What are these Semantic Web extensions I hear about?

First of all, one has to consider what the Semantic Web is intended to be. At the risk of venturing a crude definition, the Semantic Web is a means of linking together different information resources on the Internet so that they can be accessible to machine reasoning systems. By means of links between say, web pages, associations can be made between information that endows it with meaning. For example, this can lead to a more rigorous and accurate search and retrieval mechanism for data on the Internet than is possible by keyword association alone. In this way, a higher degree of confidence and trust can be placed in the results from this machine reasoning that is based on these formally defined relationships.

A (possibly oversimplified) description is that one starts with 'data models'. A data model formally expresses the relations between different data entities, eg, as in a traditional database schema. At this stage, no inference can necessarily be made on these descriptions. Indeed, the data model tends to be worked with by specific applications in which these associations are treated with much greater significance than is apparent to an external observer. So for example, one could conceive of a relational database of data that links a product to the datasets that have various analyses of it under certain flow regimes or operating conditions. This database would be used by a web site to search and retrieve this information, using application back-end code, eg, written in Java, PHP or a .NET language. In a certain sense, the knowledge of types and relations between the data entities is hidden in the application itself and is not visible to outsiders. Finally, the data models tend to be 'brittle' and easily break as different business needs arise.

So, as a consequence of this 'hidden knowledge' in the application two things arise:

  • a great deal of logic is re-implemented across different applications
  • more critically, this knowledge is hidden from, eg, collaborators or even the same organisation who may wish to exploit it.

Getting back to Wikis, a particular challenge is organising the information they contain in a way that makes sense to the user of the site. A common solution, as used in this first version of the QNET Wiki, is to 'stove-pipe' the articles into categories from some top-level downwards. So one has AC and UFR articles belonging to higher categories and so on.

The problem with this approach is the following:

  • the administrative overheads: administrators have to be very dilligent in order to classify and organise articles, inserting links into tables etc in order to make the articles accessible
  • it fixes a particular view of the articles that may not be appropriate for certain users.
  • it overlooks other very interesting relationships that may be submerged within the articles.

Ideally, one would prefer to annotate the articles themselves, ie, assign them properties that can be used for the automatic categorisation