Dear users

I wanted to replicate a paper where the authors added an astenosphere fixed velocity of 3 cm/s years. in this way, slabs would have followed this counterclockwise flow changing in angulation:

https://www.nature.com/articles/s41598-017-06551-y

So I installed the shared library “prescribed velocity” and I tried to add a counterclockwise flow of 15 cm/ years in the upper mantle:

```
subsection Prescribed velocities
subsection Indicator function
set Variable names = x,y,t
set Function constants = r_inner=5870310, r_outer=6300000
# The following line should be all on one line without the line continuation character
set Function expression = \
if(sqrt(x*x + y*y) >= r_inner && sqrt(x*x + y*y) <= r_outer, 1, 0); \
if(sqrt(x*x + y*y) >= r_inner && sqrt(x*x + y*y) <= r_outer, 1, 0)
end
# Function to define the velocity values within the annulus
# The velocity is counter-clockwise, hence Vx = -Vy and Vy = Vx
subsection Velocity function
set Variable names = x,y,t
set Function constants = r_inner=5870310, r_outer=6300000, velocity_mag=0.15
set Function expression = if(sqrt(x*x + y*y) >= r_inner && sqrt(x*x + y*y) <= r_outer, -velocity_mag*y, 0); if(sqrt(x*x + y*y) >= r_inner && sqrt(x*x + y*y) <= r_outer, velocity_mag*x, 0)
end
end
```

In this way everything is inside the upper mantle will have this flow + eventual speeds from simulations and what is outside the upper mantle won’t have it.

The point is that it doesn’t work, and the speeds that I get in general are too big, both inside and outside my annulus:

Obviously this is not what I usually have:

What is not clear to me are the order of magnitude of the speeds. Are they in m/yr? I’m I doing something wrong in my function? Any speed that i insert seems to be too big

Let me know and thank you for the help!