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Air-conditioning characteristics in nasal cavity models exhibiting nasal cycle states
Byun, Seongsu,Chung, Seung-Kyu,Na, Yang Elsevier 2019 Journal of thermal biology Vol.83 No.-
<P><B>Abstract</B></P> <P>The air-conditioning characteristics in nasal cavity models obtained from two subjects exhibiting different degrees of the nasal cycle states in terms of the airflow partition were investigated using computational fluid dynamics. A constant inspiratory flow rate of approximately 250 mL/s was considered, and the air temperature and relative humidity at the inlet were assumed to be 25 °C and 35%, respectively. The air-conditioning capacities of the congested and decongested sides were assessed by the amounts of epithelial heat and water vapor transferred to the inhaled air through the airway from the nostrils to the end of the septum. The results revealed that the air temperature and relative humidity near the end of the septum, respectively, reached approximately 31.4–32.5 °C and 81.4–88.0% in the decongested sides and 34.0–35.9 °C and 95.3–100% in the congested sides. The differences seen in the air temperatures and relative humidity between the congested and decongested sides were found to be larger in the cavity model that showed a larger degree of reciprocal change in the airflow rate. From a fluid mechanics perspective, while the congested side is in a rest period during the nasal cycle such that a lower amount of airflow is transported through it, this side, in effect, works to provide assistive air-conditioning capacity to the nasal cavity and aids when insufficiently conditioned airflow passes through the decongested side so that the inhaled air merging after the septum can approach the alveolar condition favorably through the nasopharynx.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Air-Conditioning characteristics were investigated in presence of nasal cycle states. </LI> <LI> Air temperature and relative humidity distributions were examined. </LI> <LI> Air temperature and relative humidity were higher in the congested side. </LI> <LI> The decongested side is not able to properly condition increased airflow rate. </LI> </UL> </P>
Investigation of flow characteristics in the maxillary sinus where polypoid changes develop
Chung, Seung-Kyu,Byun, Seongsu,Na, Yang Elsevier 2018 Computers in biology and medicine Vol.102 No.-
<P><B>Abstract</B></P> <P>Flow behavior in the maxillary sinus where polypoid changes develop was investigated using computational fluid dynamics. A nasal cavity model was constructed, after performing a virtual polypectomy based on computed tomography images of a patient, using a computer-aided design software to artificially remove polypoid changes inside the maxillary sinus. Local flow characteristics in the maxillary sinus were examined for one full respiration period.</P> <P>The results showed that the epithelial surfaces where polypoid changes occur are located in the lower part of the maxillary sinus which contains a protruding zone of the sinus and are characterized by stagnation of air during the entire respiration period. Due to the geometric characteristics, a very slow recirculating motion was found to occur in the bulging area for approximately half of the respiration period as a result of interaction with a larger-scale, counter-rotating vortex filling the middle of the maxillary sinus. With a much smaller velocity inside the maxillary sinus compared to that typically found in the airway passage through the middle meatus, both wall shear and pressure changes were found to be vanishingly small along the epithelial surface of the maxillary sinus where polypoid changes were found.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Virtual maxillary sinus polypectomy was performed to construct a numerical model. </LI> <LI> Flow characteristics inside the maxillary sinus were investigated. </LI> <LI> Regions where polypoid change developed in the maxillary sinus remain stagnant. </LI> <LI> Wall shear stress along the epithelial surface of the maxillary sinus is negligible. </LI> <LI> The role of wall pressure is negligible inside the maxillary sinus. </LI> </UL> </P>