I am working on human airways. My geometry is CT scan based from mouth to sixth generation. I want to run the CFD simulation for cyclic breathing (complete process of inhalation and exhalation). Could someone please help me?
Shravya, that is generally possible to split them up, but in many (most) applications you actually need to see the flow effects through the whole cycle. For instance, if you model drug delivery (sprays or fine powder), then you need to see not only how deep the particles will go, but also what percentage of them will settle inside and what percentage will be blown away on exhale stage. And in order to do that, you need to be able to model the whole cycle.
Honestly, I do not know how to do it as it is. I was modelling full blood pumping cycle in large arteries, but there the inlet is always stays inlet and outlet always stays outlet.
My suggestion would be to use Pressure Outlet at the mouth with static atmospheric pressure and Pressure Inlets at the bottom of the airways with pressure changing in time. Normally, Pressure Inlet allows both negative and positive gauge pressures and allows both directions of the flow.
Best regards,
Vitaly.
Dear Bholu,
your problem is quite difficult to solve. I have never tried to solve unsteady or transient boundary conditions in blood flow, but thinking about your problem I could suggest two approaches that may help you:
1- try te approach purposed for Shravya and simulate separately the flows, but instead of taking two separated simulations, try to start the second from the solution of the first simulation, changing the boundary inlet to boundary outlet. It is not that simple to do, and the fluent may have problem to indentify correctly the initial scenario what may be hybrid initialization, to not change what you have done before.
2 - there is a coupling possibility between Fluent and GT-power. I've never used it, but I know that is possible. The GT-power uses UDFs for coupling unsteady flows (and boundary conditions), limited in arround 20 changings. This coupling allows you to change the boundary condition in a specific time flow for another specified in the GT-power.
In spite of being hard to do, I'd try the second approach if you have time. I guess the results would be much more significant. But if you don't have time for spend in learning it, try the first it can possibly reach reasonable results if well succeed.
Best regards and hoping in being helpful.
Guilherme.
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