SimScale CAE Forum

Wall boundary condition issues

Hi, I am trying to study the convective heat transfer of breathing in a mask. I have done 2 sets of simulations, one with and one without the mask. However, both yielded very different results especially at t=0 although the boundary + initial conditions were set to be the same.

The sim without the mask worked well, however, the sim with the mask only applied boundary conditions to the intersection between the mask and the face. (See “Inhalation [Volumetric=2s]” vs “no mask [External wall heat flux derived]”)

Also, is it possible to simulate the walls of the mask as adiabatic even though it is already a porous media?

Here is the link to my project: https://www.simscale.com/projects/lli_ren/convective_breathing_sim/

Thank you in advance for your help!

Hey there!

A few remarks that can help you move forward with your simulation:

  • In a steady state simulation, the ‘time’ is only used to iterate towards the final solution. Do not compare intermediate states, just final converged ones. Also, initial conditions should not make any difference here, besides helping the solver to converge in fewer iterations.

  • If the mask is assigned as an advanced concept (porous zones in this case), then there are no walls there to apply boundary conditions.

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