Hello,

I am trying to run a 3D self consistent subduction model with traction boundary condition and particle compositional field. Before this model, I had tried free-slip condition for all boundaries and this model runs with no problem. However, when I changed the left boundary into an initial lithostatic traction boundary, I run into a problem where there are cells with no particles:

The violated condition was:

non_empty_neighbors != 0

Additional information:

A cell and all of its neighbors do not contain any particles. The

`cell average’ interpolation scheme does not support this case unless

specified in Allow cells without particles.

I tried to add minimum particles per cell, but it doesn’t seem to solve the problem. I must misunderstand this parameter. I thought it means generate new particles if a cell particles are below the limit.

I also tried to add “set Allow cells without particles = true”, and so far this model seems to be able to run but the composition near the left boundary does not keep the original composition even though I set:

set Fixed composition boundary indicators = left, right

Figure shows the oceanic plate, where the material flows in on the top left boundary is not oceanic plate any more.

Here are my boundary conditions and particles section inputs:

subsection Boundary velocity model

set Tangential velocity boundary indicators = top, bottom, front, back, right

end

subsection Boundary traction model

set Prescribed traction boundary indicators = left:initial lithostatic pressure

subsection Initial lithostatic pressure

set Representative point = 0, 0, 660000

end

end

subsection Particles

set Number of particles = 75000000

set Minimum particles per cell = 50

set Allow cells without particles = true

set Time between data output = 2e6

set Data output format = vtu

set List of particle properties = velocity, initial composition

set Interpolation scheme = bilinear least squares

set Update ghost particles = true

set Particle generator name = random uniform

subsection Interpolator

subsection Bilinear least squares

set Use linear least squares limiter = true

end

end

end

Is there a way to create new particles at the left boundary when material flows in while using traction boundary condition? How to keep the inflow the same composition as the initial condition?

Thank you.