Examinando por Autor "Nielsen, P.V."

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  • Miniatura
    Publicación
    Influence of the geometry of the airways on the characterization of exhalation flows. Comparison between two different airway complexity levels performing two different breathing functions
    (Elsevier, 2020-02) Berlanga Cañete, Félix Antonio; Liu, L.; Nielsen, P.V.; Jensen, R.L.; Costa, Alexandre; Olmedo, I.; Ruiz de Adana, M.
    Human exhalation can emit pathogens in droplets that can represent the origin of airborne cross infections. Simplified respiratory airway models have been used in experimental and numerical studies in order to simulate exhalation flows. This study presents a comparison between two different airway models, a simplification (SA) and a realistic 3D scanned model (RA) in performing two different exhalation patterns corresponding to two different female metabolic rates, corresponding to a standing relaxed (SR) activity (1.2 met) and walking active (WA) metabolic level (2 met). A time resolved particle image velocimetry (TR-PIV) study of the flow emitted to the surroundings in each case is obtained for each airway and exhalation combination. Results show that the scanned 3D model (RA) presents a different and more realistic flow development. Transient puff structures have been identified for both airway models. Results can be useful for further research on pollution control in indoor and outdoor spaces.
  • Miniatura
    Publicación
    Three dimensional analysis of the exhalation flow in the proximity of the mouth
    (Elsevier, 2024-02-29) Berlanga Cañete, Félix Antonio; Gómez del Pino, Pablo Joaquín; Esteban Paz, Adolfo; Liu, L.; Nielsen, P.V.
    The human exhalation flow is characterized in this work from the three-dimensional velocimetry results obtained by using the stereo particle image velocimetry (SPIV) measurement technique on the flow emitted from a realistic airway model. For this purpose, the transient exhalation flow through the mouth of a person performing two different breaths corresponding to two metabolic rates, standing relaxed (SR) and walking active (WA), is emulated and studied. To reproduce the flow realistically, a detailed three-dimensional model obtained from computed tomography measurements on real subjects is used. To cope with the variability of the experimental data, a subsequent analysis of the results is performed using the TR-PIV (time resolved particle image velocimetry) technique. Exhalation produces a transient jet that becomes a puff when flow emission ends. Three-dimensional vector fields of the jet velocity are obtained in five equally spaced transverse planes up to a distance of Image 1 from the mouth at equally spaced time instants Image 2 which will be referred to as phases (φ), from the beginning to the end of exhalation. The time evolution during exhalation of the jet area of influence, the velocity field and the jet air entrainment have been characterized for each of the jet cross sections. The importance of the use of realistic airway models for the study of this type of flow and the influence of the metabolic rate on its development are also analyzed. The results obtained contribute to the characterization of the human exhalation as a pathway of the transmission of pathogens such as SARS-CoV-2 virus.