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Nose air flow (Respiratory cycle) simulation with heat and Humidity exchange

    • AHMED ALI
      Subscriber

      Dear All, Greetings. I would like to simulate the airflow of the nose using the following parameters: 

      Time: inspiration takes 1.9 s and expiration 2.3 s (4.2 s for one complete cycle).

      Temperature and Humidity: The inspired air had a temperature of 20 C and 30 % relative humidity. The expired air had a temperature of 35 C  and a relative
      humidity of 100 %. The temperature of the nasal mucosa (Wall) increased from 30 C to 34C. The moisture of the nasal mucosa (Wall) was set to be constant at 100 %

      Pressure: To simulate the inspiration, a negative pressure is set in the nasopharynx (Outlet) between 0 and -10 Pa. This led to a flow speed of up to 2 m/s around the middle turbinate. For the expiration, the pressure in the nasopharynx (Outlet) was set between 0 and 10 Pa.

      I have successfully generated the mesh and defined the Inlet, Wall and Outlet. I would appreciate help setting the physics step by step. Especially how to make the model dynamic - expiration and inspiration. Include humidity and heat. 

      I use Ansys student 2023, also have full version at school.

      I hope someone has time for this. Referring me to similar tutorials or posts is great too.

      Please check out this study for more information: https://drive.google.com/file/d/1nEIVnxOQuzmX9-GZLYBOVWuAS3ua5Hup/view?usp=sharing 

      Best regards

      Looking forward to hearing from you soon

      *Can't attach the full file for patient privace.

       

       

    • Rob
      Ansys Employee

      Break the setup into parts - it's easier to learn and troubleshoot on. I also suggest doing the test runs on a pipe bend. It's near enough the same but will run/fair far more quickly. 

      For the boundaries review Profiles and Expressions. I think the latter would be better. Also consider whether you want to push or pull flow and in which direction. 

      Look for humidity on here - it's simple but not set quite as you've asked for. 

    • AHMED ALI
      Subscriber

      Thank you so much Rob. I'm following your instruction. will get back to you soon

       

    • Rob
      Ansys Employee

      Very likely.... ;) 

      As an aside, do NOT use velocity boundaries at both ends. You need velocity at one end and pressure at the other: fixing flow at both boundaries is a really bad idea. 

    • AHMED ALI
      Subscriber

       

      Thanks, Rob, I've been looking around since last time, trying to figure it out. here is what I reached so far; 

      1- In Physics> Models> I have to activate Energy, Viscous, and Species in order to calculate heat transfer between the ‘wall’ and Fluid, apply turbulence (after Renolds number calculation), and simulate humidity exchange (water condensation and evaporation) between the ‘wall’ and the fluid.

      2- In Material> add mixture template of Air and Water-vapor.

      3- cell zone is set to fluid> material is> Mixture-template

      4- Boundaries;

                  Inlet> Velosity-inlet, 20C, H2O 0.3

                  outlet> Pressure-outlet, -5 P, 35C, H2O 1.

                 Wall> wall, Thermal or heat flux, 30C/34C, H2O (specifiec mass fraction = 1)

      5- The inspiration and the expiration should be simulater separately; the time of each can be determined by adjusting the time step size and the number of time steps.

      Here are my target parameter for convenience;

      Kindly take a look and instruct me.

       

       

       

    • Rob
      Ansys Employee

      If the gas mixture is fixed (no reason for it not to be) then outlet pressure doesn't matter: read how the velocity bc works. 

      For the wall have a look at the species flux options. 

       

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