Vertical Pipe water flow
 

I have validated the water flow in horizontal circular pipe using 2D axi-symmetric model (x direction->horizontal and y direction->radial) under laminar, transition and turbulent flow regime.

Now I want to use vertical pipe with and without boussinesq approximation.

For Without boussinesq approximation case:

In operating condition panel, I set the gravity on along x direction = -9.81.

I completed the simulation, and found that radial V, T and local Nu along the pipe is same as horizontal pipe. Only difference is Pressure drop is lower for vertical pipe. How to know the results are correct?

For With boussinesq approximation case:

In operating condition panel, I set the gravity on along x direction = -9.81. Also set the operating temperature which is same as inlet temperature.

In material panel, constant density is replaced by Boussinesq and value of beta is set.

I completed the simulation and found that velocity profile form like M-shape which I think correct. But wall temperature along the pipe becomes smaller than bulk temperature.

I am bit more confused. Is there any reference research papers related to this? Any suggestions please .

Thanks

GS