Prescribe outlet boundary condition with flow file

[Yun Shi]

I can measure the volumetric flow rate of outlets with PCMRI. Can the outlet boundary condition be prescribed with flow file instead of RCR in next version of SimVascular?

[Yun Shi]

Justin mentioned the outlet could be set velocity=0 in prescribed velocities surface so as to occlude the outlet.Does it mean that prescribed velocities can not only be used to prescribe the inlet BC but also the outlet BC?

Link to viewtopicPhpbb.php?f=188&t=8915&p=0&start=0&view=

[Weiguang Yang]

Yes, you may prescribe a flow waveform on an outlet as you did for an inlet but this is not recommended. If you just have a flow rate for that outlet, it is better to use a resistance or RCR outflow BC that achieve the measured flow rate.

[Yun Shi]

Thank you, Weiguang! It is difficult to estimate the capacitance and the ratio of proximal and distal resistance of three-elements Windkessel model. Thus, I can hardly prescribe RCR to approximate the flow waveform obtained from PCMRI. Can you tell me something in details why it is not recommend to prescribe flow waveform in outlet?

[Weiguang Yang]

Prescribing Dirichlet BCs at outlets requires pre-knowledge of the flow conditions/velocity profile. The velocity profile at an outlet depends on upstream information and is usually unknown. When you use the inflow waveform type inflow BC (it is a Dirichlet BC in Simvascular) you enforce a velocity profile at the outlet in which does not usually have an idealized profile.

[Yun Shi]

The problem of parabolic velocity profile imposed on outlet truly exists. Can this problem be partly resolved by adding cylinders to the end of visceral arteries?

model.png (81.03 KiB) Viewed 560 times

[Weiguang Yang]

I am not sure but you can try that.

[Yun Shi]

I see. Thank you