Problems to set Variable Pressure with Deformable Wall condition

[Michela Garau]

Hello,

I am currently working on a 3D simulation of an aortic vessel. I was able to properly simulate the unsteady condition by using an inflow wave, the windkessel model and the rigid wall condition.
However, when I change the rigid wall condition in a deformable wall condition, the results does not seem to consider the windkessel parameters which I imposed in "Inlet and Outlet BCs" section anymore, but they tend to flatten out to the unique value of pressure that I must defined in the wall properties section, as show in the attached figures.

The last commands in the .svpre file appears like this:
...
deformable_wall_vtp mesh-complete/walls_combined.vtp
deformable_thickness 0.2
deformable_E 6.04e6
deformable_nu 0.5
deformable_kcons 0.833333
deformable_pressure 126000
deformable_solve_displacements
wall_displacements_write_vtp displacement.vtp
write_geombc geombc.dat.1
write_restart restart.0.1
...

Looking at the svPre commands at page https://simvascular.github.io/archiveFl ... olverSec71, in the " Deformable walls with uniform thickness and elastic modulus" section, I can understand there is the possibility to change the line "deformable_pressure 126000", in order to read a file in which pressure corresponds to the proper variability through time. Is it the correct approach or is there another way to get the outlet variable pressure? Any suggestions are well appreciated.
Thanks in advance

Michela

[Weiguang Yang]

Can you check if the inflow BC is correctly imposed? It seems there is no pulsatile flow in the model. Make sure you have the same svpre command for the inlet as that used in the rigid case. You can also compare the bct.dat files that prescribe the inlet velocities. The bct.dat files should be the same in both cases since you keep the inflow waveform unchanged.thx

[Michela Garau]

Hi Weiguang,

thank you for your reply. Unfortunately I think this is not the problem: the inflow waveform seems correctly imposed as you can see in the Fig_1 attached

Fig_1.png (14.8 KiB) Viewed 335 times

related to Flow rate at the inlet and outlet faces by using the inlet.flow waveform, the 3element windkessel model and the deformable (constant) wall condition.

Moreover the .svpre command for the inlet is the same for both simulations.
.svpre files for rigid case:

mesh_and_adjncy_vtu mesh-complete/mesh-complete.mesh.vtu
set_surface_id_vtp mesh-complete/mesh-complete.exterior.vtp 1
set_surface_id_vtp mesh-complete/mesh-surfaces/Anonima.vtp 2
set_surface_id_vtp mesh-complete/mesh-surfaces/Carotide.vtp 3
set_surface_id_vtp mesh-complete/mesh-surfaces/Discendente.vtp 4
set_surface_id_vtp mesh-complete/mesh-surfaces/Inlet.vtp 5
set_surface_id_vtp mesh-complete/mesh-surfaces/Succlavia.vtp 6
fluid_density 1.06
fluid_viscosity 0.04
initial_pressure 0
initial_velocity 0.0001 0.0001 0.0001
prescribed_velocities_vtp mesh-complete/mesh-surfaces/Inlet.vtp
bct_analytical_shape parabolic
bct_period 1
bct_point_number 201
bct_fourier_mode_number 20
bct_create mesh-complete/mesh-surfaces/Inlet.vtp Inlet.flow
bct_write_dat bct.dat
bct_write_vtp bct.vtp
pressure_vtp mesh-complete/mesh-surfaces/Anonima.vtp 0
pressure_vtp mesh-complete/mesh-surfaces/Carotide.vtp 0
pressure_vtp mesh-complete/mesh-surfaces/Discendente.vtp 0
pressure_vtp mesh-complete/mesh-surfaces/Succlavia.vtp 0
noslip_vtp mesh-complete/walls_combined.vtp
write_geombc geombc.dat.1
write_restart restart.0.1


.svpre files for deformable case:

mesh_and_adjncy_vtu mesh-complete/mesh-complete.mesh.vtu
set_surface_id_vtp mesh-complete/mesh-complete.exterior.vtp 1
set_surface_id_vtp mesh-complete/mesh-surfaces/Anonima.vtp 2
set_surface_id_vtp mesh-complete/mesh-surfaces/Carotide.vtp 3
set_surface_id_vtp mesh-complete/mesh-surfaces/Discendente.vtp 4
set_surface_id_vtp mesh-complete/mesh-surfaces/Inlet.vtp 5
set_surface_id_vtp mesh-complete/mesh-surfaces/Succlavia.vtp 6
fluid_density 1.06
fluid_viscosity 0.04
initial_pressure 126000
initial_velocity 0.0001 0.0001 0.0001
prescribed_velocities_vtp mesh-complete/mesh-surfaces/Inlet.vtp
bct_analytical_shape parabolic
bct_period 1
bct_point_number 201
bct_fourier_mode_number 20
bct_create mesh-complete/mesh-surfaces/Inlet.vtp Inlet.flow
bct_write_dat bct.dat
bct_write_vtp bct.vtp
pressure_vtp mesh-complete/mesh-surfaces/Anonima.vtp 0
pressure_vtp mesh-complete/mesh-surfaces/Carotide.vtp 0
pressure_vtp mesh-complete/mesh-surfaces/Discendente.vtp 0
pressure_vtp mesh-complete/mesh-surfaces/Succlavia.vtp 0
deformable_wall_vtp mesh-complete/walls_combined.vtp
deformable_thickness 0.2
deformable_E 6.04e6
deformable_nu 0.5
deformable_kcons 0.833333
deformable_pressure 126000
deformable_solve_displacements
wall_displacements_write_vtp displacement.vtp
write_geombc geombc.dat.1
append_displacements restart.0.1


In order to be clearer, I briefly describe the procedure I followed in the attached pdf :

Simulation_procedure.pdf

(165.81 KiB) Downloaded 27 times

I notice one your response on post "Fails to apply initial conditions for deformable wall simulation", Posted on Mon Sep 16, 2019
Maybe is something related to the same problem, but I am trying to follow your instructions

Assume the restart file for the last step in a rigid simulation is restart.100.0.
Copy it to your current simulation dir. and rename it as restart.0.1
In your svpre file, remove "initial_pressure 0" and "initial_velocity 0.000 0.000 0.000".
Rerun the presolver script in the command line by typing "svpre xxxx.svpre"

But I am still not able to achieve a good solution.
The IC File should appear somewhere in the .svpre or in the solver.inp files?

Thanks,

Michela

[Weiguang Yang]

I notice a couple of missing commands in the svpre file.

After you set deformable_wall_vtp mesh-complete/walls_combined.vtp

I think you need to add:
fix_free_edge_nodes_vtp mesh-complete/walls_combined.vtp

This command tells the solver to clamp all nodes on the rings of the inlets and outlets.
You also also need add:
deformable_create_mesh_vtp mesh-complete/walls_combined.vtp

Then a deformable solve displacement is executed.
Run the svpre solver again and see if it works.

[Michela Garau]

Hi Weiguang,

thank you so much! Now the job seems well working

Bests

Michela