In the subduction model I want to constrain the velocity inside the model, and I falsed.

I need some help to solve the problem, and this is my aspect input file. Without the prescribed velocity partion it runs correctly.

set Output directory = output

set Use years in output instead of seconds=true

set World builder file = /data3/Changs/inputpara/47ridgesub-wb.wb

set Dimension = 2

set CFL number = 0.1

set End time = 4e6

set Pressure normalization =no

set Max nonlinear iterations = 100

set Nonlinear solver tolerance = 1e-4

set Nonlinear solver scheme=single Advection, iterated Stokes

set Resume computation= auto

set Additional shared libraries= /home/dealii/aspect/cookbooks/prescribed_velocity/libprescribed_velocity.so

set Prescribe internal velocities= true

subsection Prescribed velocities

subsection Indicator function

set Variable names=x,y,t

set Function expression = if(((x<950e3) & (x>700e3) & (y>580e3) & (y<650e3)),1,0);if(((x<950e3) & (x>700e3) & (y>580e3) & (y<650e3)),1,0)

end

subsection Velocity function

set Variable names=x,y,t

set Function expression= 0.066;-0.001

end

end

subsection Solver parameters

subsection Stokes solver parameters

set Number of cheap Stokes solver steps = 0

end

end

subsection Geometry model

set Model name = box

subsection Box

set X extent = 2000e3

set Y extent = 660e3

set X repetitions = 50

set Y repetitions = 17

end

end

subsection Material model

set Model name = visco plastic

set Material averaging = harmonic average

subsection Visco Plastic

set Reference temperature=273

set Thermal diffusivities=9.89e-7,1.21e-6,1.21e-6,1.15e-6,9.87e-7,1.21e-6,1.15e-6,9.87e-7

set Specific heats = 750.0

set Densities = 3300,3300,2800,2900,3300,3300,3300,3300

set Thermal expansivities =2e-5

set Angles of internal friction=25,10,20,20,20,22,22,25

set Cohesions=20e6,10e6,20e6,20e6,20e6,10e6,10e6,20e6

set Prefactors for diffusion creep=2.37e-15,1.e-50,1.e-50,1.e-50,2.37e-15,1.e-50,1.e-50,2.37e-15

set Prefactors for dislocation creep=6.52e-16,1.12e-10,8.57e-28,7.13e-18,6.52e-16,1.12e-10,1.12e-10,6.52e-16

set Stress exponents for dislocation creep=3.5,3.4,4.0,3.0,3.5,3.4,3.4,3.5

# set Stress exponents for diffusion creep=1

```
set Activation energies for diffusion creep=375.e3,0,0,0,375.e3,0,0,375.e3
set Activation energies for dislocation creep=530.e3,497.e3,223.e3,345.e3,530.e3,497.e3,497.e3,530.e3
set Activation volumes for diffusion creep=4.0e-6,0,0,0,4.e-6,0,0,4.e-6
set Activation volumes for dislocation creep=13.e-6,0,0,0,18.e-6,0,0,18.e-6
set Grain size exponents for diffusion creep=3,1,1,1,3,1,1,3
set Minimum strain rate=1.e-20
set Reference strain rate=1.e-15
set Minimum viscosity=1e20
set Maximum viscosity=1e26
set Reference viscosity=1e22
set Viscosity averaging scheme= maximum composition
set Viscous flow law=composite
set Elastic shear moduli=75.0e9,50.0e9,75.0e9,75.0e9,75.0e9,100.0e9,100.e9,100.e9
end
```

end

subsection Compositional fields

set Number of fields = 7

end

subsection Initial composition model

set Model name = world builder

end

subsection Gravity model

set Model name = vertical

subsection Vertical

set Magnitude = 9.8

end

end

subsection Mesh refinement

set Initial adaptive refinement = 2

set Initial global refinement = 0

set Time steps between mesh refinement = 0

set Strategy = minimum refinement function

subsection Minimum refinement function

set Coordinate system = cartesian

set Variable names = x,y

set Function expression = if(y>300.e3,if(y>460.e3,2,1), 0)

end

end

subsection Formulation

set Formulation = custom

set Mass conservation = ask material model

set Temperature equation = reference density profile

end

subsection Initial temperature model

set Model name = world builder

end

subsection Boundary temperature model

set Fixed temperature boundary indicators=2,3

set Model name = box

subsection Box

set Bottom temperature = 1713

set Top temperature = 273

end

end

subsection Boundary velocity model

set Prescribed velocity boundary indicators = left:function

set Tangential velocity boundary indicators = right,bottom

end

subsection Boundary velocity model

subsection Function

set Variable names = x,y

set Function constants = Va=0.066

set Function expression = if(y>580e3,Va,0);0;

end

end

subsection Boundary composition model

set Fixed composition boundary indicators = bottom, left

set List of model names = initial composition

end

subsection Mesh deformation

set Mesh deformation boundary indicators=top:free surface

subsection Free surface

set Free surface stabilization theta=0.5

set Surface velocity projection = vertical

end

end

subsection Postprocess

set List of postprocessors = visualization,temperature statistics,topography,heat flux map

subsection Visualization

set List of output variables = heat flux map

set Time between graphical output = 1e5

set Interpolate output = true

end

end