I am trying to run a simple model that consists of an extruded circle (forming a cylinder).
The set up is such that a fluid flows through the interior of the cylinder/pipe and there is a heat flux applied on the wall. However, when I read the results for the Nusselt Number, I get incorrect values (compared to literature). When I set heat flux to 0 and set a higher temperature at the wall to simulate heat transfer, the curve for the Nusselt number is more representative of the values I should be getting.
How should I set up my model ?