[MITgcm-support] problems at tile bdys?

[Jody Klymak]

Hi All,

I ran a simulation in a 2-D channel but three-D in setup, and all ran fine.  Well except it stayed 2-D because there was nothing to cause there to be spanwise motion.  The simulations are nonhydrostatic.  

So, I added a very small amount of three d by a few different methods, and everytime, no matter how I set up the three dimensionality (bottom roughness, initial velocities, surface displacements) there would an instability at the same spot in x.  It turns out it is a tile boundary in the middle of the domain.  

I'm using advection scheme 33, and chnaged OLx and OLy to 5, but still the same problem.  I tried a few other advection schemes, with the same issue (it happens in a hundred or so timesteps, so its easy to debug, at least).  I also tried upping the iterations on the CG3d solver, but that didn't help at all.

I've now gone back to the same setup I started with, but changed by tile layout (half as many tiles), and the instability is gone.  

Has anybody run into this?  Any suggestions for a fix or what to look for?  (I guess the stupid fix is not to use that tile configuration, but that seems flakey).

Thanks,   Jody


--
Jody Klymak    
http://web.uvic.ca/~jklymak/