Heat flux coefficient at VOF interphase
 

Hi

I'm currently running a simulation of an oil bubble rising in water. The bubble has a lower temperature than the continuous water-phase. My target is to evaluate the heat fluxcoefficient at the interphase between water and the oil bubble.

Setup:
3D-Mesh with quads
VOF (not coupled level set)
Energy equation on
ic: 0 velocity flow field, spherical patched bubble with phase 2 for oil
bc: walls and gravity

In my opinion the result of the rising bubble looks plausibel, the temperature distribution over time too.

https://www.cfd-online.com/Forums/at...1&d=1494408144

https://www.cfd-online.com/Forums/at...1&d=1494408147

But if I want to evaluate the heat flux coefficient by doing the following steps I get 0 w/2-k:
- Create an isosurface with a VOF value of 0.5
- Reports/Surface Integrals
- Choosing Area Weighted Average, and surface heat transfer coefficient under wall fluxes
- choosing the isosurface and evaluate

If I plot the heat flux as a contour plot on the isosurface I also only get 0 w/m^2. But my temperature field tells me an other story. Is it actually possible to evaluate the heat flux at the interface? And if so, how?

Best
Andy