I'd like to add some new info that can help fix the problem. Today I tried to change the thermal-oil to air so that both sides are the same fluid and I got correct results, which means that the problem happens only when the 2 materials are not the same.nI guess this is happening due to some sort of averaging that happens between cells of different fluids which is not supposed to happen. I am not sure which fluid property is causing this problem exactly? Is it the large difference in densities between air and thermal-oil? or is it viscosity?nThere must be a way to prevent this from happening. nAny advise?n