[CFDJonas]

Hello,

I'm currently working on the CFD simulation of a tubular reactor. The geometry I want to model is astoundingly simple: a long tube with just an inlet, outlet and a wall. No bends, no built-ins, no valves, no injections. The diameter is however rather small compared to the length. Inside the whole reactor a volumetric reaction takes place. During this, my focus is to look at the boundary layer at the wall.

Although this setup seems very easy to generate a mesh from, I'm a little bit overtaxed with which criteria are important for me. My current setup is to have a rectangle with a axial symmetry axis at the reactor center. Do I need inflation layers? Do I only need inflation layers, when I want to incorporate turbulences (but not for laminar flow)? Is it a valid thought, that I need a finer mesh "at the beginning" but a coarse mesh later in the reactor? How does diffusion take an effect when talking about mesh quality? Does a transient simulation of the process require a finer mesh?

What would an ideal mesh look like, for a simple long laminar tube (I know there's analytic solution for this, but I want to take this as an example).

Thanks in advance!