Fanno Rayleigh flow in pipes
 

Hi,

Just a thought, but can commerical CFD solvers be used to model Fanno / Rayleigh flows?

Fanno flow requires a friction factor to be exact, so is it possible to consider a friction factor in the solver, or is it accounted for in the turbulence model?

Can Rayleigh flow be turbulent? Rayleigh flow neglects friction, but CFD solver apply wall laws, thus creating friction or is that a different 'type' of friction?

Any thoughts?

hi dave,
i just had done a test simulation on rayleigh flow in fluent. I used invisid model with heat source,and results from simulation matched perfectly with reyleigh invisd relation. Mach number increase from 0.3 to 1.
Next i am going to run it with turbulence model. Let see what happen......!

Yeah, both can be done.

Analytically you would probably assume it constant along the duct and then calculate, so is it not more interesting to use CFD to obtain it as an output? If you want though, there are ways to define such a boundary condition - details depend on the software. :)

Can you explain more detaily the process?

I need more information about the setup for the Rayleigh simulation. Can you please explain?