Large Eddy Simulation help

PattiMichelle

I'm a physicist experimenting with reacting flows with PHOENICS 3.4 and 3.6. I want to look at the Large Eddy Simulation (LES) turbulence model which PHOENICS has. So as a started, I'm looking at vonKaraman vortex shedding from a circular cylinder, which is fairly easy - using library case 808 as a starting point, and the laminar flow setting in the proper reynolds number range. Setting relaxations can be quite tricky and depends rather strongly on grid fineness and the presence or absence of fine grid embedding. As soon as I turn the LES model on, all vortex shedding disappears, even though I'm in the correct reynolds number range to see it. I notice there are settings for the prandtl/schmidt numbers in the LES turbulence settings - doesn't PHOENICS calculate them itself as necessary? Are these merely factors to tune those settings? I've tried both steady and unsteady solutions and I've even tried restarting the LES model from a LAMINAR solution with a well-developed vonKaraman vortex street - it just disappears!

Can someone share their experience with how to set up the LES turbulence model and get physically realistic solutions? I would very much appreciate any help I can get, as well as a possible reference as to how to set the LES model parameters (schmidt/prandtl numbers).

Thank You Very Much, pattiMichelle