Negative Aorta Flow Convergence Issue
 

Hello all,

First of all thank you for the support provide to the CFD community with this forum.

I am using a transient model to analyze the aorta blood flow. My boundary conditions are a mass flow waiveform at the aorta inlet and the Windkessel model at the outlet. I am using Piso solver. My problem is that the aorta waiverform has a negative peak (reflux through the aorta valve), once the simulation reaches this negative value the solution diverges. I have tried to reduce the time step, to use an adapative time step, to refine the mesh, but nothing worked.
Did anybody experience the same problem?

Thank you in adavance.

when you have reflux, I suppose two things can happen: 1) the walls are elastic and the volume diminuishes or 2) the walls are rigid and you have reverse flow from the outlet.

I think you have to describe better your model and check if the BC.s are able to satisfy the continuity equation for all the conditions.

is that a laminar flow
 

Are you using a laminar flow model?... I think it would be an improvement to use transitional model in all this applications like the k-kl-omega model or the mos recent one k-omega-v2 model ("Prediction of transitional and fully turbulent flow using an alternative to the laminar kinetic energy approach")