Fig 2. Boundary conditions for input, output, and alveolar sacs with computational mesh.

Ventilated waveform of flow rate at inlet G10, pressure waveform at all outlets (this figure shows pressure boundary condition at the outlet G20), and pressure waveform at the alveolar sac, were considered as boundary conditions for the 50-year-old and 80-year-old lungs. For the computational mesh, solid and fluid mesh elements of bronchioles were approximately 229,791 and 832,960; and for alveolar sacs they were approximately 82,530 and 201,432 respectively. The solid part was simulated on a single tissue layer.