[javierstokes]

Hey all,

I am running a simulation on a bifurcated geometry (image attached).

I am unsure what I should take to be my characteristic length when computing the Reynolds number. I was originally going to use the inflow diameter (as is standard), but someone pointed out to me that the maximum length between the bottom of the lower branch and top of the upper branch (around x=6) will also have as much, if not more impact on the flow profile. This makes sense as well.

Ultimately I suppose it's inconsequential, as I can always compute both Reynolds numbers and report them separately (which is not unheard of), but I'm interested to know what the standard approach is in a geometry like this.

Thanks!

[FMDenaro]

The physics is always the same, independently from the lenght you use.
Any choice you want to do will produce a Reynolds number that is formally correct, you have only to decide the lenght that more properly characterizes your flow problem. This is more relevant in solving the non-dimensional form of the equations where you expect that a proper lenght will produce non dimensional values of O(1).