[lobstar]

Hi,

Does anyone know the value of wall roughness used by fluent when the enhanced wall treatment option is selected? I'm aware that you can't set a value when you select this option. what I'd like to know is what value Fluent uses when calculating the flow or how it calculates that value. I ran a series of flows through a thin pipe using an axis-symmetric k-e model with enhanced wall treatment. I also ran a simulation with standard wall functions and set the value to zero. The results were different which suggests that fluent gives the walls a roughness value. I also carried out some theoretical calculations for the flow rate with different wall roughnesses for comparison to my enhanced results. It appears that the value of wall roughness used by fluent changes with the size of the geometry. If anyone could offer any guidance I would be very appreciative.