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Hi,
our MRI data shows backflow by the outflows of renal arteries (the inflow is in the aorta) but our simulations are not able to show any backflow. We are trying everything, e.g., boundary conditions, mesh elements, tolerances... Can the backflow stabilization coefficient (here 0.2) limit/suppress the backflow from outflows?

Hello,

Which solver are you using?

Backflow stabilization is used to prevent flow reversals at outflow boundaries representing truncated vascular regions (i.e. where the entire artery is not modeled explicitly). You will probably need to model a good portion of the renal geometry.

To have any hope of matching experimental data you will need to

- Use boundary conditions that match experimental data

- Tune your outlet boundary conditions to identify the RCR constants

- Have a mesh that is fine enough to capture the flow features you are interested in

- Run the simulation long enough (1000s of time steps maybe) for it to converge to a periodic solution

You might need to use FSI, check the literature to see what others have done.

Cheers,
Dave

Thank you.

Different simulations are carried out with very wide ranges of spatial and temporal accuracies, and for this reason we think the cause of the missing backflow is something else. I'm not sure if the solution should be to extend the vessel (hopefully beyond the backflow) or if the simulations can't use a Backflow stabilization coefficient (i.e., with the coefficient null). What do you think? Thank you.

Hello,

The proper solution would be to model the renal vessels with their outflow boundary as far away from the junction with the aorta as possible. The backflow stabilization correction is only applied at the outlet boundaries.

You also need to understand what might could be causing the backflow. Is it all flow physics or is there a physiological aspect that is not being modeled by the outlet boundary conditions.

Cheers,
Dave