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Underground hydrogen storage represents an innovative approach to energy storage. To ensure the secure operation of subterranean hydrogen storage strings, a computational fluid dynamics (CFD) methodology was employed to devise an erosion assessment model tailored for high-velocity conditions. The research delved into the erosion and abrasion dynamics of these storage strings when subjected to high-speed gas flows. This study further examined the impacts of gas velocity, particle size, pipe material, and pipe wall corrosion imperfections on flow patterns and erosion wear rates across the column. The outcomes revealed several noteworthy trends. As fluid velocity increased, the flow field's maximum pressure augmented, while it decreased alongside enlarging pipe diameter and particle size. P110 pipe material exhibited higher maximum pressure in comparison to N80. The effect of centrifugal force induced pressure to surge from the inner to the outer portion of the column. In the curved pipe section's outer wall, the frequent occurrence of high-angle collisions engendered elevated rates of erosion wear over time. Particularly noteworthy was the observation of the highest erosion rate in curved pipes showcasing three corrosion defects, attributed to the backflow effects of erosion pits. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to evaluate the effects of nasal surgery on airflow characteristics in patients with obstructive sleep apnea (OSA) by comparing the alterations of airflow characteristics within the nasal and palatopharyngeal cavities. Methods: Thirty patients with OSA and nasal obstruction who underwent nasal surgery were enrolled. A pre- and postoperative 3-dimensional model was constructed, and alterations of airflow characteristics were assessed using the method of computational fluid dynamics. The other subjective and objective clinical indices were also assessed. Results: By comparison with the preoperative value, all postoperative subjective symptoms statistically improved (p < 0.05), while the Apnea-Hypopnea Index (AHI) changed little (p = 0.492); the postoperative airflow velocity and pressure in both nasal and palatopharyngeal cavities, nasal and palatopharyngeal pressure differences, and total upper airway resistance statistically decreased (all p < 0.01). A significant difference was derived for correlation between the alteration of simulation metrics with subjective improvements (p < 0.05), except with the AHI (p > 0.05). Conclusion: Nasal surgery can decrease the total resistance of the upper airway and increase the nasal airflow volume and subjective sleep quality in patients with OSA and nasal obstruction. The altered airflow characteristics might contribute to the postoperative reduction of pharyngeal collapse in a subset of OSA patients. [ABSTRACT FROM AUTHOR]

Nasal septal deviations (NSD) have been categorized into 7 types. The effect of these different deviations on airflow pattern and warming function has not been fully investigated. The purpose of this study was to utilize a computational fluid dynamics approach to assess the impact of NSD of varying types on nasal airflow and warming function. Patients with each type of NSD were enrolled in the study, and a normal participant as the control. Using a computational fluid dynamics approach, modeling of nasal function was performed. Indices of nasal function including airflow redistribution, total nasal resistance, airflow velocity, and airflow temperature were determined. Among all types of NSD, the maximal velocity and total nasal resistance were markedly higher in type 4 and 7 deviations. The flow partition and velocity distribution were also altered in type 4 and 7 as well as type 2 and 6 deviations. Airflow in all categories of NSD was fully warmed to a similar degree. From a computational aerodynamics perspective, the type of septal deviation may contribute to altered airflow characteristics. However, warming function was similar between septal deviation types. Future studies will help to ascertain the functional importance of septal deviation types and the applicability of these computational studies. [ABSTRACT FROM AUTHOR]

Background: A concha bullosa (CB) of the middle turbinate is frequently observed on the nondeviated side of patients with a nasal septal deviation (NSD). However, the impact of the CB on nasal airflow characteristics in patients with NSD has been incompletely defined. Objective: The purpose of this study was to evaluate the impact of a CB in patients with NSD on nasal airflow characteristics using a computational fluid dynamics (CFD) approach. Methods: Twenty patients with NSD and a unilateral CB of the middle turbinate on the nondeviated side (study group) were recruited. Another 20 patients with NSD without the formation of a CB (control group) were also enrolled. Using CFD, the maximal airflow velocity, nasal resistance, maximal wall shear stress, and minimal temperature in the bilateral nostrils of each group were assessed. Moreover, the volume of the nasal tract, surface area-to-volume ratio, and the total nasal resistance were compared between the study and control groups. Results: In the study group, no significant differences of airflow dynamics between the bilateral nasal cavities were observed. In the control group, however, there were statistically significant differences for maximal airflow velocity, nasal resistance, maximal wall shear stress, and minimal airflow temperature between the bilateral nostrils. The surface area-to-volume ratio and total nasal resistance in the study group was significantly higher and the nasal volume was significantly decreased than that in the control group. Conclusion: CB of the middle turbinate on the nondeviated side of patients with NSD rendered airflow characteristics more evenly distributed between the bilateral nostrils as assessed by CFD. From an aerodynamics perspective, a CB may represent a compensatory action to normalize airflow dynamics. However, a CB may also result in constriction of the ipsilateral nasal cavity. [ABSTRACT FROM AUTHOR]

Background: The functional significance of the posterior segment of the septum is not fully understood. Aims/Objectives: The purpose of this study was to evaluate the impact of posterior septum resection with varying extents on nasal airflow pattern and warming function, and to determine the appropriate resection extent on posterior septum without disturbing airflow pattern. Material and Methods: Three dimensional models were established from the nasal CT scan of a healthy female volunteer without nasal disease. The models included the normal, as well as 1 cm, 2 cm, and 3 cm extent of posterior septum resection by virtual surgery. Using computational fluid dynamics, the airflow characteristics such as average and peak airflow velocity, average wall shear stress, average temperature and turbulence kinetic energy were recorded and compared among the four models. Results: By comparison with the normal model, the virtual surgeries with varying extents of posterior septum resection (1 cm, 2 cm, and 3 cm), demonstrated little alteration on indices of the average and peak airflow velocity, average wall shear stress, airflow temperature and turbulence kinetic energy. However, a statistical difference of the abovementioned indices existed when compared between varying planes of the nasal cavity (p <.001), although this did not appear to be significantly influenced by the degree of posterior septectomy. Conclusions and significance: From an aerodynamics perspective, little disturbance on airflow pattern and warming function of nasal cavity could be detected with increasing resection of posterior septum (up to 3 cm). These results may imply that resection of the posterior septum (up to 3 cm) has little impact on nasal function. [ABSTRACT FROM AUTHOR]

In this work, a comprehensive multiphysics model is developed in-house to numerically predict microalgae productivity in concentric-tube internal loop airlift photobioreactors (PBRs). The program integrates solar radiation, light attenuation in microalgae suspensions, cell growth kinetics, and hydrodynamics. The simulations of light attenuation and cell growth kinetics are based on experimental data measured in a PBR. The gas–liquid bubbly flow hydrodynamics is simulated using computational fluid dynamics (CFD) (Ansys FLUENT). The program is employed to predict the annual biomass areal and volumetric productivities of PBRs with various geometrical and operating parameters. The governing equations for the model integration are numerically solved using the finite-volume method for spatial discretization and an explicit scheme for time integration with a time step of PBR liquid circulation time. The effects of plant latitude, shading, clearance between adjacent PBRs, PBR dimension, downtime, and harvesting biomass threshold concentration on the annual biomass productivities are investigated. Under the assumptions made in this study, it is found that the 2.5 m-high PBRs yield higher annual areal biomass productivity than the 1.5 m- and 2 m-high PBRs. The highest productivity is found at a plant latitude of approximately 15°. The optimal harvesting threshold concentration for the highest annual areal productivity is in the range of 0.4–0.7g l−1 depending on the downtime. The optimal concentration increases with longer downtime. Small clearances between adjacent PBRs are preferred to offer higher areal productivity. For PBRs positioned with small clearances, PBRs with smaller diameter-to-height ratios are more advantageous since the higher land utilization efficiency outweighs the increased shading loss. [Display omitted] • A comprehensive multiphysics program is developed in-house to assess outdoor PBRs. • The program integrates radiative transfer, kinetics, and hydrodynamics. • Light attenuation and growth kinetics modeling is based on PBR experimental data. • Arrayed PBRs are evaluated by annual areal and volumetric biomass productivities. • Effects of PBR geometrical and operating parameters are investigated. [ABSTRACT FROM AUTHOR]

Conclusion:From aspect of fluid dynamics, expanding patients’ nasopharyngeal coronal-sectional area to 48.3–54.7% of normal area will bring the airflow velocity back to normal in adenoidal hypertrophy children. It might provide a suggestion for adenoidectomy range selection and whether total resection is necessary. Objectives:To evaluate the nasopharyngeal airflow characteristics in pediatric OSA patients with adenoidal hypertrophy, and to explore the proper resection range for adenoidectomy Method:Nine OSA patients and four normal children were recruited. The CT scans of their upper airway were collected and used to construct three dimensional models for fluid dynamics analysis. Using computational fluid dynamics, indices such as velocity, pressure, and coronal-sectional area were calculated. Results:Compared with the normal, the OSA children showed three characteristics in nasopharyngeal: the airflow velocity was significantly higher (p < 0.05), the coronal-sectional area was significantly smaller (p < 0.01), while pressure showed no difference (p > 0.05). In a study of the relationship between velocity and coronal-sectional area, this study investigates different coronal-sectional areas from 30–300 mm2. It was found that, when patients’ nasopharyngeal coronal-sectional area was expanded over 155–170 mm2, namely 48.3–54.7% of normal area, airflow velocity in nasopharyngeal showed no difference than normal. [ABSTRACT FROM PUBLISHER]

Objectives/Hypothesis: To compare the aerodynamic differences around ostiomeatal complex between the convex side and concave side in patients with concurrent nasal septal deviation and chronic rhinosinusitis, and to explore the potential correlation between nasal septal deviation and chronic rhinosinusitis occurrence from the perspective aerodynamics. Study Design: Retrospective case series. Methods: Fifty-six patients with concurrent nasal septal deviation and chronic rhinosinusitis were recruited. Nasal septal deviation was divided into mild, moderate, and severe deviations according to deviation angle. Using computational fluid dynamics, indices such as maximal velocity, maximal turbulence kinetic energy, maximal wall shear stress, and minimal temperature around the ostiomeatal complex were calculated and compared between the convex side and concave side, and among patients with varying severities of deflection. Results: The proportion for mild, moderate, and severe deviations was 12.5%, 32.1%, and 55.4%, respectively. Significant differences for maximal velocity, maximal wall shear stress, maximal turbulence kinetic energy, and minimal temperature around the ostiomeatal complex between the convex side and concave side could be detected. No significant difference of aerodynamic characteristics around the osteomeatal complex could be detected with the increasing of deviation angles. The incidence for chronic rhinosinusitis in convex, concave, and bilateral sides was 16.1%, 25%, and 58.9%, respectively. Conclusions: From the aerodynamics perspective, both sides of nasal cavity have the potential to predispose the occurrence of chronic rhinosinusitis in patients with nasal septal deviation. The increased deviation angle did not aggravate aerodynamic disturbance around the osteomeatal complex. The contributing role of nasal septal deviation in the pathogenesis of chronic rhinosinusitis should not be emphasized in excess. Laryngoscope, 2012 [ABSTRACT FROM AUTHOR]