[pezarello86]

Hi,
i am trying to simulate the natural convection phenomena between a cold pipe (external surface of -2 °C) and a warmer water (about 4 °C). the objective is to estimate the external natural covnection coefficient in order to investigate the potential ice formation onto pipe surface(through an iterative procerure already implemented on MATLAB which needs of this coefficient).
I created the mesh on icem CFD to obtain a yplus about of 1 and i am using different turbulence model: from k eps RNG to k-omega and SST but i obtain very different results. From literature i found the formula for the coefficient estimate: if i use k eps with standard wall function my results agree with formula but with k-omega and SSS arevery different. In order to achieve the convergence i applied very low under relaxiation factor in steady state simulations. From a comparison with two run with standard k epsilon, one steady state and the other one transient, the results are the same.
could someone help me please?
Thanks to all