[lr103476]

Hi,

I am validating OpenFOAM using Fluent on a static circular cylinder at Re=150.

The full grid and a zoom are shown here:
full grid
grid zoom near the cylinder

I used the following schemes:
ddtSchemes
{
default CrankNicholson 0.5;
}
gradSchemes
{
default Gauss linear;
grad(p) Gauss linear;
}
divSchemes
{
default none;
div(phi,U) Gauss linear;
}
laplacianSchemes
{
default none;
laplacian(nu,U) Gauss linear corrected;
laplacian(1|A(U),p) Gauss linear corrected;
}
interpolationSchemes
{
default linear;
interpolate(HbyA) linear;
}
snGradSchemes
{
default corrected;
}
fluxRequired
{
default no;
p;
}

The standard ICCG and BICCG solvers are used untill convergence to resectively 1e-6 and 1e-5 is obtained. The time step was chosen to be 0.02, which corresponds to 250 timesteps within each vortex shedding cycle.

Also the standard boundary conditions are applied:
inlet: U fixed and zeroGradient for p
outlet: p fixed and zeroGradient for U
upper/lower boundary: symmetry

I investigated the drag and lift which were comparable for both solvers, Fluent and OpenFOAM, but the vorticity plots show strange artifacts.

The following figures show these vorticity plots of both solvers:
vorticity Fluent zoom view
vorticity Fluent full view
vorticity OpenFOAM zoom view
vorticity OpenFOAM full view

When comparing the zoom views it appears that certain 'secondary' vortices occur which are not allowed to exist. It appears that the numerical diffusion is different between Fluent and OpenFOAM. OpenFOAM gives a reasonable solution, but not yet good enough. I also used blended and quick differencing but with comparable results.

Is someone having any ideas on how to improve these simulations? Do I use the proper schemes? Is the mesh of sufficient quality?

Thanks,
Frank