Study of nanoparticles deposition in a human upper airway model using a dynamic turbulent Schmidt number

In this paper, the nanoparticles deposition in the upper portion of the human respiratory system is studied by using a dynamic turbulent Schmidt number. The flow and particle governing equations are solved using large eddy simulation (LES) with a localized dynamic subgrid scale closure of the residual stress tensor and the scalar flux term. The flow solution and the particle transport are dynamically coupled and thus, the turbulent momentum and mass diffusivity are calculated from the resolved flow and particle concentration fields. The methodology is applied to an extrathoracic oral airway model for several particle diameters ranging from 10 nm to 52 nm at a breathing rate of 30 L/min. The results are compared to the previously published RANS and experimental data. It is observed that the current methodology improves the quality of results for flow and particle deposition considerably. It is also noticed that the turbulent Schmidt number is quite different from its typically assumed values. Keywords: LES, Nanoparticles deposition, Upper airway model, Dynamic turbulent Schmidt numbe

Study of nanoparticles deposition in a human upper airway model using a dynamic turbulent Schmidt number

In this paper, the nanoparticles deposition in the upper portion of the human respiratory system is studied by using a dynamic turbulent Schmidt number. The flow and particle governing equations are solved using large eddy simulation (LES) with a localized dynamic subgrid scale closure of the residual stress tensor and the scalar flux term. The flow solution and the particle transport are dynamically coupled and thus, the turbulent momentum and mass diffusivity are calculated from the resolved flow and particle concentration fields. The methodology is applied to an extrathoracic oral airway model for several particle diameters ranging from 10 nm to 52 nm at a breathing rate of 30 L/min. The results are compared to the previously published RANS and experimental data. It is observed that the current methodology improves the quality of results for flow and particle deposition considerably. It is also noticed that the turbulent Schmidt number is quite different from its typically assumed values. Keywords: LES, Nanoparticles deposition, Upper airway model, Dynamic turbulent Schmidt numbe

Vector aeroacoustics for a uniform mean flow: acoustic velocity and vortical velocity

Acoustic and vortical disturbances in uniform mean flow bounded with solid surfaces are investigated in this paper. A convective vector wave equation and a convection equation which describe, respectively, the acoustic velocity and vortical velocity in uniform mean flow are deduced by combining the Helmholtz-Hodge decomposition method with the method of Mao et al. (AIAA Journal, 2016, 54(6): 1922-1931). Analytical acoustic velocity integral formulations for the monopole and dipole sources in uniform mean flow are deduced from the developed vector wave equation, and are also verified through numerical test cases. Moreover, this paper clarifies that aerodynamic sound is radiated from the monopole source as well as the irrotational components of the dipole and quadrupole sources. The solenoidal parts of the dipole and quadrupole sources are acoustically non-radiating but they induce vortical disturbances in uniform mean flow