Definition of Delta

[rmojgani]

py2d/py2d/Py2D_solver.py

Line 115 in d2ab972

Delta = 2 * Lx / NX

Checking @gyf135 code,

Definition of $\Delta$ here seems to be wrong

It should be

    Delta = L / NX

or for 2DHIT case to

    Delta = 2 * np.pi / NX

to match

https://github.com/envfluids/2D-DDP/blob/0542ca9dfeed3948b452d1307b85fddad6e82c25/physics-based%20codes/SMAG/F2DHIT_DSMAG.py#L80

@jakharkaran can you confirm this and it's downstream effects?

[jakharkaran]

The Delta is usually proportional to the grid size, L/NX. I have been using Delta = twice the grid size (FGR=2, Filter width to grid size ratio).
Pavel's paper analyzes FGR in Appendix B1 for decaying turbulence. They use FGR=\sqrt(6)
https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2023MS003771

I plan to do a similar analysis for py2d at some point, and we can find an optimum FGR for our system. For now, you can consistently use the same FGR across all your runs.