View source for Benchmark ercoftac ufr2-02

= ERCOFTAC UFR 2-02: Flow past a square cylinder =

== Description ==
For a full description of the case see:<br>
http://qnet-ercoftac.cfms.org.uk/index.php?title=Flow_past_cylinder <br>
or <br>
[http://cfd.mace.manchester.ac.uk/cgi-bin/cfddb/prpage.cgi?43&EXP&database/cases/case43/Case_data&database/cases/case43&cas43_head.html&cas43_desc.html&cas43_meth.html&cas43_data.html&cas43_refs.html&cas43_rsol.html&1&0&0&0&0 here]

U_in = 0.54 m/s with 2% turbulence<br>
Re_D = 22 000<br>

Size of the square cylinder is 0.04 m wide and 0.392 m high.<br>
Its situated in a tunnel with a width of 14D = 0.56 m.<br>
[[File:urf2-02-domain.png | 300px | computational domain ]]

== Results ==
'''Experimental results'''<br>
The Strouhal number is around 0.132<br>
Drag coefficient is around 1.9-2.2<br>

'''OpenFOAM results'''<br>
The grid here, and in the supplied example, is too coarse really. But it's nice for testing different setups before doing the ''real'' simulation<br> 
and its good enough to be used for mapping if you want to run on a fine mesh without the initial start-up.<br>
[[File:urf2-02-Cd.png | 300px | OpenFOAM Cd results ]] [[File:urf2-02-Cl.png | 300px | OpenFOAM Cl results ]]<br>
The drag coefficient fluctuates a bit, but after 5-6 seconds the average settles around 2.04.<br>
The calculated Strouhal value in the above picture is around 0.135.<br>
<math>
St = \omega \frac{D}{U} = \frac{D}{\tau U}
</math>

== Notes ==
In the case directory there is a perl script called ''generateMeshDict.pl''.<br>
This script will generate the blockMeshDict file given input arguments. To see what they are just run it without any input arguments and
it will write some helpful usage info.<br>

If you want to run a 2D simulation just edit the generateMeshDict.pl and remove the comment infront of $nz.<br>

<pre>
my $nz = int(0.2*$H1/$dx) + 1;
#$nz = 1;
</pre>

and change the wall bc to empty for lowerUpper patches<br>
<pre>
    print "    wall lowerUpper\n";
</pre>

== Download == 
The application to use is '''pimpleFoam''' and the case can be downloaded [http://openfoam.nequam.se/cases/ufr2-02.tgz here ]

== References == 
This list only contains references that can be obtained for free and that are not subject to any copyright infringement...I hope.<br>

* http://www.tfd.chalmers.se/~lada/postscript_files/ahmad_corsica.pdf
* http://www.tfd.chalmers.se/~lada/postscript_files/ahmad_ASME-JSME_paper.pdf

It is just a small list that is by no means complete, since I dont want to copy it from the ercoftac database.<br>

--[[User:Niklas|Niklas]] 13:29, 24 April 2010 (UTC)