TY  - JOUR
AB  - To enhance understanding of the airflow characteristics in the human respiratory system during realistic inspiration, we investigated the airflow field in a human upper airway model using large eddy simulation and the dynamic grid method, taking into account clinically measured inspiratory characteristics. The results reveal the following novel findings: (1) The laryngeal jet and recirculation zone exhibit significant unsteadiness, with their dynamic characteristics primarily influenced by the transient inspiration flow rate and glottis motion. This pattern holds true for other airflow characteristics as well. (2) Glottis expansion reduces the energy consumed during inhalation for both steady and unsteady inspiratory flow rates, with the degree of expansion being directly related to the reduction in energy. We can accurately predict power loss by considering the glottis area and inspiratory flow rate. (3) Analysis of spectral entropy clearly demonstrates that the flow transitions from the laminar to turbulence earlier when using clinical inspiration data. Turbulence intensity in the trachea increases when either glottis motion or the transient inspiratory is ignored. In conclusion, the airflow dynamics are significantly more unsteady compared to cases where we ignore either glottis motion or the transient inspiratory flow rate. A precise understanding of realistic respiratory airflow cannot be achieved by assuming either a rigid glottis or a steady inspiration pattern. Therefore, it is crucial to use accurate inspiratory data when studying the properties of airflow structures in the human respiratory system. Moreover, incorporating more physiological data is also essential to obtain realistic respiratory airflow characteristics.
AU  - Jing, H.*
AU  - Ge, H.*
AU  - Wang, L.*
AU  - Choi, S.*
AU  - Farnoud, A.
AU  - An, Z.*
AU  - Lai, W.*
AU  - Cui, X.*
C1  - 68826
C2  - 53697
CY  - 1305 Walt Whitman Rd, Ste 300, Melville, Ny 11747-4501 Usa
TI  - Investigating unsteady airflow characteristics in the human upper airway based on the clinical inspiration data.
JO  - Phys. Fluids
VL  - 35
IS  - 10
PB  - Aip Publishing
PY  - 2023
SN  - 1070-6631
ER  - 

TY  - JOUR
AB  - Chronic rhinosinusitis is a common disease worldwide, and the frequently prescribed nasal sprays do not sufficiently deliver the topical medications to the target sites so that the final treatment in severe cases is surgery. Therefore, there is a huge demand to improve drug delivery devices that could target the maxillary sinuses more effectively. In the present study, different particle diameters and device pulsation flow rates, mainly used in pulsating aerosol delivery devices such as the PARI SINUS (R), are considered to evaluate optimal maxillary sinus deposition efficiency (DE). Numerical simulations of the particle-laden flow using a large eddy simulation with a local dynamic k-equation sub-grid scale model are performed in a patient-specific nasal cavity. By increasing the pulsation flow rate from 4 l/min to 15 l/min, nasal DE increases from 37% to 68%. Similarly, by increasing the particle size from 1 mu m to 5 mu m, nasal DE increases from 34% to 43% for a pulsation flow rate of 4 l/min. Moreover, normalized velocity, vorticities, and particle deposition pattern in different regions of the main nasal cavity and maxillary sinuses are visualized and quantified. Due to the nosepiece placement in the right nostril, more particles penetrate into the right maxillary sinus than into the left maxillary sinus despite the maxillary ostium being larger in the left cavity. Lower pulsation flow rates such as 4 l/min improve the DE in the left maxillary sinus. The use of 3 mu m particles enhances the DE in the right maxillary sinus as well as the overall total maxillary drug delivery.
AU  - Farnoud, A.
AU  - Tofighian, H.*
AU  - Baumann, I.*
AU  - Garcia, G.J.M.*
AU  - Schmid, O.
AU  - Gutheil, E.*
AU  - Rashidi, M.M.*
C1  - 60442
C2  - 49314
CY  - 1305 Walt Whitman Rd, Ste 300, Melville, Ny 11747-4501 Usa
TI  - Large eddy simulations of airflow and particle deposition in pulsating bi-directional nasal drug delivery.
JO  - Phys. Fluids
VL  - 32
IS  - 10
PB  - Amer Inst Physics
PY  - 2020
SN  - 1070-6631
ER  -