# 1 ERCOFTAC UFR 2-02: Flow past a square cylinder

## 1.1 Description

For a full description of the case see:
http://qnet-ercoftac.cfms.org.uk/index.php?title=Flow_past_cylinder
or
here

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

Size of the square cylinder is 0.04 m wide and 0.392 m high.
Its situated in a tunnel with a width of 14D = 0.56 m.

## 1.2 Results

Experimental results
The Strouhal number is around 0.132
Drag coefficient is around 1.9-2.2

OpenFOAM results
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
and its good enough to be used for mapping if you want to run on a fine mesh without the initial start-up.

The drag coefficient fluctuates a bit, but after 5-6 seconds the average settles around 2.04.
The calculated Strouhal value in the above picture is around 0.135.
$St = \omega \frac{D}{U} = \frac{D}{\tau U}$

## 1.3 Notes

In the case directory there is a perl script called generateMeshDict.pl.
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.

If you want to run a 2D simulation just edit the generateMeshDict.pl and remove the comment infront of $nz. my$nz = int(0.2*$H1/$dx) + 1;
#\$nz = 1;


and change the wall bc to empty for lowerUpper patches

    print "    wall lowerUpper\n";