Searching for unstable eigenmode near turbulent transition.

[ethrelfall]

Dear community,

I have a script that searches for unstable eigenmodes of a convective flow (is zucatti.py in the repo referenced below).

A paper called "Assessment of reduced-order modeling strategies for convective heat transfer" shows a nice time-harmonic oscillation for Rayleigh number 3.4E5 and I am trying to find the same mode in Firedrake (I can do it in a time-domain solver in the Nektar++ spectral elements code - see repo).

My Firedrake eigenanalysis does not seem to find this mode - can anyone help as to why / how to fix (any hints gratefully received, e.g. am I just asking too much of the numerics?).

More info and my script can be seen at

https://github.com/ethrelfall/Flow-stability

(Searched matchnig discussions - nowt.)

Thanks!