[ziyasaydam]

Hello everyone,

I wonder if anyone has conducted sailing yacht drag analysis with multiphase option in STAR-CCM. I am comparing experimental results of different size models with my analysis in STAR-CCM.

My major problem in all these analysis is being unable to find the right wall treatment. After finding the right size of cells for the free surface, wake regions and surrounding regions of the hull, keel and rudder -all being the same size-, I keep halving the size of cells on the surfaces of the hull, keel and rudder (to decrease the Y+ values) until the solution becomes grid independent. Note that during this approach, I adjust the time step in order to obtain a Courant Number of around 1-10.

With this approach, different size and different geometry models become grid independent at very different Y+ values. On a 6 meter model case the solution became grid independent at Y+ values of ~500, whereas on a 2.4 meter model as I decrease the Y+ from 400 towards 50, I keep deviating from the experimental results...

Does anyone have an idea about possible reasons for inconsistencies in the results? My expectation was to see that the results get reasonably closer to experimental results as I decrase Y+ towards ~50...

Thanks in advance,

Ziya