[CIG-LONG] GALE: under resolved cells with flux boundary conditions

[Marco Billia]

Hi there!

I have a problem concerning under resolved cells with the calculation of 
each time step within my model. The message I get is: /
Something went horribly wrong in _PCDVC_Calculate2D: Problem has an 
under resolved cell (Cell Id = XY), check or tune your population 
control parameters/. However, I am able to calculate as many time steps 
I want but the particle density clearly differs from the one at the 
beginning.
If I turn the third dimension on and induce additional VC's in the 
z-direction I get the following message after the first tstep:
/Error in _PCDVC_Calculate3D: Problem has an under resolved cell (Cell 
Id = XY), add more particles to your model. Error running Underworld 
(revision unknown) - Signal 11 'SIGSEGV' (Segmentation Fault)/ and Gale 
aborts.

To my model:
I'm essentially pushing a soft block against a rigid indenter (viscosity 
ratio=50) to get an idea about the particle-paths during exhumation 
within the hanging wall in a big fault zone. The boundary conditions are 
the following:

StressBC top: y-value is a hydrostatic term
StressBC bottom: supporting stress with y-value=1
WallVC left: vx=0, vy=0 (in 3D: vz=1)
WallVC right: vx=0, vx=-2 (in 3D: vz=-1)

All boundaries are static whereas the Inflow-condition is turned on.

I tried to reduce vx left and increased the particlesPerCell-value 
and/or the grid resolution. No change. There is a pressure singularity 
in the lower left corner because of the no-slip condition but that's an 
unrelated issue I guess. The 2D- and 3D-script are attached.

Thanks for any kind help!

Cheers,
Marco

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