Changing the inflow velocity in a steady flow simulation

[Justin Tso]

Hi, I've noticed that when changing the velocity of a steady flow simulation, the simulation results exhibit some unexpected behavior. For example, using a certain velocity results in steady results, but using a velocity of 1.5 times the original or two-thirds of the original results causes the flow and pressure at the outlet to steadily increase over time. Can anyone explain why this is occurring and what it would require to fix it? I'm using the simple prescribed resistance outlet boundary condition, and I would think that this shouldn't be changed, as the vessel geometry is the same between simulations.

[Melody Dong]

Hi Justin,

Do the pressure and flow results ever converge eventually? For some simulations, the pressure/flow at outlets may steadily increase for a few timesteps before converging to a steady result and you may need to run the simulation for a few more timesteps before convergence. However, this is moreso the case with more complicated boundary conditions and deformable wall simulations.

You can also check that the velocity you prescribe is correct by viewing the bct.vtp fie in Paraview. This file should be generated in your simulation folder when you create simulation files. It contains a 3D visualization of the velocity you prescribe at the location you prescribe it. You can load the bct.vtp and walls_combined.vtp (from the mesh folder generated) into Paraview, then select the "warp by vector" option for the bct.vtp file in Paraview to see which direction the velocity is being prescribed.

Refer to the SimVascular documentation on prescribing flow in your simulation to ensure that you follow those steps correctly: http://simvascular.github.io/docsFlowSo ... l#inflowbc


Best,
Melody