Fast computation of time-dependent acoustic fields

We present a method for the fast evaluation of time-dependent acoustic fields from complex sources. The technique is based on a fast integration method for the boundary integral arising in a Kirchhoff formulation and requires a small, and roughly constant, computation time to compute a transient signal, at the expense of a pre-processing stage. In our calculations, based on test cases for a single rotor and a counter-rotating open rotor, we find that transient field calculations require an order of magnitude less computational time for the field from an array of~16384 sources, a computational advantage which increases with source number

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