The Innovative CFD website, has a section with articles themed on tips and tricks as well as the common questions posed by CFD users. It covers a large part of the aspects dealt with with respect to CFD simulations.
Worth checking out, whether a beginner or experienced !
Having recently joined the corporate environment, it was pleasant to see first hand, the kind of support that is available to customers via the ANSYS customer portal; tutorials and help files are readily accessible. Though a lot of the material is available online via other sources, the latest updates can be found via the portal.
ANSYS products are a commercial (and costly!) software suite and access to a machine with a working installation is required. I will try to focus on resources which are openly accessible and useful in beating the learning curve. This should minimize your search for good tutorials and provide a jump start; An ANSYS section has also been added in Resources, collating the individual resources mentioned on this blog.
It is common in Universities to host tutorial files within their intranet and have the help files set up locally, rather than provide access to the Customer portal. The academic versions of ANSYS provide limited modules. There are other Universities and researchers who partner with ANSYS in releasing books and official tutorials that cover the ANSYS suite of products. It's important to know as much as possible about the tool that is being used to perform the simulation and generate the results on which we base our analysis.
The tutorials put up by Cornell University are time-less in the way they have usually been the starting point in academics. The above link has sections on structural analysis, CFD ( using Gambit and Fluent) as well as MATLAB. A great set of tutorials with categories starting from the beginner to the advanced level is accessible at the website maintained by the University of Alberta, which also has a post processing tutorials section, though the sections are focused on structural analysis.
Gambit is now a dated pre processing application; it may be more useful to get familiar with a commercial tool like ICEM or even open source tools like Salome, Gmsh, Engrid. Pheonix Analysis & Design technologies have a periodic electronic publication called The Focus, which is available for free and all the past articles are also archived. This magazine has articles that are very useful and unlike the usual kind of articles that are found on the web, they are professional and meant for the general ANSYS user, with interesting aspects explored.
ANSYS.net is a highly reccomended source, both by The Focus magazine mentioned above and other websites as well. It also contains free to download macro's and tips and tricks regarding ANSYS. However, there doesn't seem to be much of CFD related applications in it. Writing macro's is also an important skill to cultivate, as it aids in automation and saving time.
One should pay a visit to the official ANSYS website as well as blog, which is more often focused on events where the ANSYS products have been used along with the occassional foray into emerging areas where ANSYS is being used. There is also a tips and tricks section which is useful. The free webinars hosted by ANSYS, on various topics are posted on this blog and it includes a tips and tricks section too.
Xansys is a ANSYS community portal that is fairly active. The forum seems more focussed on FEM related structural applications, which is what ANSYS was known for initially. The most useful feature and the reason why Xansys is being mentioned is the ANSYS Links page. A few of the links are outdated and don't work and the main links are posted in this article. This page contains links to the most prominent and prolific resources related to ANSYS, covering reviews, tutorials, product updates and information about other software applications and the industry as well.
There is an active ANSYS forum on CFD-online as well, with subforums categorised based on products, like CFX and Fluent as well as another related to the Pre processing.
Additional Links : (This section will be updated as and when I find new resources )
The notion that Open Source Software (OSS) is difficult to master or apply is slowly melting away. Infact, current 'mainstream' Linux distributions are developing along the lines of being very user friendly to the extent that the interface affects the core functionality and flavor of the distribution. The latest Ubuntu Unity version for example has impressive graphics and several bells and whistles attached to the UI to provide a Mac like feel, using Compiz. The above is in comparison with Ubuntu 10.04 on which CAE-Linux is based. It may interest you to know that the Mac is a customised Unix based OS.
Which Linux Distribution ? Linux distributions basically have different flavors or interfaces. An analog would be : the different versions of Windows. However, I believe Microsoft intend to do away with the versions in Windows 8. The most popular interfaces on Linux are the Gnome and KDE. Ubuntu and Kubuntu are examples of the Gnome and KDE flavors. SUSE is an OS further customised available with a KDE base or Gnome. I think SUSE has slightly tougher learning curve than Ubuntu, though the workspace customisation options are simply delightful. Ubuntu is known to make operating systems extremely user friendly. For example, Ubuntu 10.04 LTS is a lot like a tweaked Windows XP. It's something that is easy to get used to.
There are Linux distributions that are tailor made for specific purposes. The website Distrowatch covers the latest releases, news and reviews related to Linux distributions and worthy of a visit. There are free Linux guide books available for download on the website, but there is a lengthy registration process.
Anyhow, there are enough easily accessible resources on the internet to master Linux. Have a look at the Learning Linux Section as well.
Personally, I have also found SUSE's enhanced KDE interface very interesting, with the concept of grouping folders via panels. SUSE however, takes a noticably longer time to startup and definitely feels slower than CAE Linux. However, on downloading the KDE desktop and interface via CAE Linux, there was a problem of missing menu items. In this case, it was the all important CAE Linux Menu. The short cuts were available, but had to be individually typed in the search bar, and the solution was to add a panel with the short cuts on the desktop.
Recent articles have alluded to the thought process and possibly popular opinion that Microsoft has been losing ground to the Apple products' sheer might and appeal, rather than Open Source or Linux. The ultimate appeal of OSS is that it is free and gives one the possibility of actually controlling applications, their output and automate any aspect at all.
Conventionally, the industry was limited to writing User Defined Functions (UDF's) and hooking them up to commercial solvers. It should also be noted that the majority of servers and supercomputers were and even now, usually run on Linux. The most successful case of Linux being used commercially is that of Red Hat Enterprise Linux. They provide the source code but not do not provide the compiled binaries. Red Hat changed the status quo by providing Support (and relatively expensive support), the much needed ingredient to bolster OSS. CentOS is a free distribution based on the Red Hat source code. It is known to work best as a Server based OS.
As a conclusion to the kind of OS you should choose : Ubuntu's distributions have the most user friendly interface and is ideal for a beginner. CAE Linux is one distribution to consider in that case. SUSE and Geeko CFD is also another option, but is known to make the installation of packages, a little more complicated than the well known apt-get command in Debian and Ubuntu or the very friendly package manager. Once you have gained a footing, Fedora/Debian/SUSE may be the distributions to turn to for more power and maximum stability. It really depends on the type of environment you deploy the system and whether it's a desktop or a Server.
'The best software' ? Let us say, one does take the plunge OSS, to understand the mechanics and the codes solving all our simulations. Often, irrespective of OSS or Commercial applications, when it comes down to choosing the software package, questions and possibly involuntary thoughts occur related to 'choosing the best software'. Such questions can especially be seen in forums regarding 'which CFD software is the best'. This question does not have any direct answer. In CFD, to the largest extent possible,the code's performance should strictly be measured against valid experimental results. This should hold the same of any code. It's fair to say that OSS is not 'better' than Commercial software. The vice versa also holds true. These are just different platforms with their characteristic features. Contributions and opinions of experienced members in forums indicate the above as well. Infact, the performance of a solver, solving a particular kind of physics must be evaluated rather the software package itself. For example, Gambit, despite it's limitations was very widely used and is still being used by both academic and industrial users. The majority swear by commercial pre processors like ICEM, ICEPAK, HyperMesh etc. These tools are known to get the job done, which is very important in the industry. It would seem that User Friendliness, is an aspect that comes in at the very end. Most software that come out nowadays, are however user friendly enough.
The question of OSS being more difficult is more often because of possibly steeper learning curve, which in turn is rather an issue of unlearning the things we're used to. Somebody familiar with computers in an intimate manner could get used to the Command Line interface and Linux pretty quickly.
Discussion : For example, I recently had a go at cross checking an OpenFoam (OF) installation on the latest Ubuntu Unity version, while providing an overview of the key elements that make up an OF simulation. Such a check would simply involve running blockMesh and the solver, say icoFoam and then starting Paraview to post process.
I found that the new shortcut bar on the desktop was a little bothersome to get used to, but it was definitely not the kind of OS anybody need to be afraid of. However one should remember, running OF and installing different applications will very often require libraries and an active internet connection is the most convenient way to get up and running quickly and relatively painlessly.
This is where the advantage of a pre-compiled distribution like CAE-Linux or Geeko-CFD is undeniable. There are usually no missing libraries and application shortcuts are available in the CAE-Linux group in the Start Menu. This is quite useful for those that are too apprehensive of the Command Line Interface.
An effort is being made to write up this experience, information and relevant resources on CFD-Wiki on CFD-Online, the most popular portal of CFD. The section under development is titled 'The Open Source Section'. The more personal information and views will be put up on this blog.
When approaching Linux and moving away from GUI cushioned applications with heavy commercial support, one should remember that even seasoned Command Line users copy & paste commands and look up commands as well, frequently. It's more important to read up on things and take a plunge by getting an Open Source distribution at your disposal. Preferably something like CAE-Linux. I've experienced no issues regarding missing libraries so far.
Of course, eventually, one can anyway come up with a more suitable distribution if and when required - by learning how! Ubuntu 10.04 has inbuilt options to customise a distribution. Another point to note is that using a Linux Operating system with a Command Line interface and considering the overall architecture/methodology on which OF is built on, requires a thinking pattern/approach that is more proactive and focussed on more intelligent thinking and maneuverability.
However, there are studies, not more than 3 years old that evaluate the preprocessing capabilities of applications like Salome, GMsh and Elmer. The author of one such paper, deemed that Salome is the closest that these OSS come up, against industrial veterans like Ansys and Altair. Results have been obtained from OF which are reliable, but time is of essence , in terms of being suitable to industrial applications. Few have the expertise and the time to devote to implementing a system and also taking care of debugging and maintenance.
Conclusion (.. for now ) In terms of uncomplicated everyday use, like emails, web browsing and media, OSS and operating systems can definitely serve your purpose well. The problem arises when you have to extensively use MS Office applications. I intend to find a work-around for this bottleneck soon. Antiother issue is support. Not many are fully conversant with Linux OS's and one has to be prepared to exercise his brains, looking for solutions on the internet.
In terms of CFD and CAE, open source applications definitely offer performance that is noteworthy of comparison with commercial solvers. But the Pre and Post processing capabilities, which is extremely important, still have much to cover. The biggest strength is how things can be automated using simple BASH or Python scripts.