OBJECTIVE: The triply periodic minimal surface (TPMS) Gyroid porous scaffolds were built with identical porosity while varying pore sizes were used by fluid mechanics finite element analysis (FEA) to simulate the in vivo microenvironment. The effects of scaffolds with different pore sizes on cell adhesion, proliferation, and osteogenic differentiation were evaluated through calculating fluid velocity, wall shear stress, and permeability in the scaffolds. METHODS: Three types of gyroid porous scaffolds, with pore sizes of 400, 600 and 800 μm, were established by nTopology software. Each scaffold had dimensions of 10 mm × 10 mm × 10 mm and isotropic internal structures. The models were imported to the ANSYS 2022R1 software, and meshed into over 3 million unstructured tetrahedral elements. Boun- dary conditions were set with inlet flow velocities of 0.01, 0.1, and 1 mm/s, and outlet pressure of 0 Pa. Pressure, velocity, and wall shear stress were calculated as fluid flowed through the scaffolds using the Navier-Stokes equations. At the same time, permeability was determined based on Darcy' s law. The compressive strength of scaffolds with different pore sizes was evaluated by ANSYS 2022R1 Static structural analysis. RESULTS: A linear relationship was observed between the wall shear stress and fluid velocity at inlet flow rates of 0.01, 0.1 and 1 mm/s, with increasing velocity leading to higher wall shear stress. At the flow velocity of 0.1 mm/s, the initial pressures of scaffolds with pore sizes of 400, 600 and 800 μm were 0.272, 0.083 and 0.079 Pa, respectively. The fluid pressures were gradually decreased across the scaffolds. The average flow velocities were 0.093, 0.078 and 0.070 mm/s, the average wall shear stresses 2.955, 1.343 and 1.706 mPa, permeabilities values 0.54×10^-8 1.80×10^-8 and 1.89×10^-8 m² in the scaffolds with pore sizes of 400, 600 and 800 μm. The scaffold surface area proportions according with optimal wall shear stress range for cell growth and osteogenic differentiation were calcula-ted, which was highest in the 600 μm scaffold (27.65%), followed by the 800 μm scaffold (17.30%) and the 400 μm scaffold (1.95%). The compressive strengths of the scaffolds were 23, 26 and 34 MPa for the 400, 600 and 800 μm pore sizes. CONCLUSION The uniform stress distributions appeared in all gyroid scaffold types under compressive stress. The permeabilities of scaffolds with pore sizes of 600 and 800 μm were significantly higher than the 400 μm. The average wall shear stress in the scaffold of 600 μm was the lowest, and the scaffold surface area proportion for cell growth and osteogenic differentiation the largest, indicating that it might be the most favorable design for supporting these cellular activities.
Tissue Scaffolds/chemistry* ; Porosity ; Finite Element Analysis ; Osteogenesis ; Cell Differentiation ; Cell Proliferation ; Tissue Engineering/methods* ; Hydrodynamics ; Humans ; Stress, Mechanical ; Cell Adhesion

In order to solve the problems of difficult test, high cost and long cycle in the development of large-scale airborne negative pressure isolation system, the simulation analysis of negative pressure response characteristics is carried out around various aviation conditions such as aircraft ascending, leveling and descending, especially rapid decompression, based on the computational fluid dynamics (CFD) method. The results showed that the isolation cabin could achieve -50 Pa pressure difference environment and form a certain pressure gradient. The exhaust air volume reached the maximum value in the early stage of the aircraft's ascent, and gradually decreased with the increase of altitude until it was level flying. In the process of aircraft descent, the exhaust fan could theoretically maintain a pressure difference far below -50 Pa without working; Under the special condition of rapid pressure loss, it was difficult to deal with the rapid change of low pressure only by the exhaust fan, so it was necessary to design safety valve and other anti-leakage measures in the isolation cabin structure. Therefore, the initial stage of aircraft ascent is the key stage for the adjustment and control of the negative pressure isolation system. By controlling the exhaust air volume and adjusting parameters, it can adapt to the change of low pressure under normal flight conditions, form a relatively stable negative pressure environment, and meet the needs of biological control, isolation and transport.
Aircraft ; Computer Simulation ; Aviation/instrumentation* ; Humans ; Hydrodynamics ; Air Pressure ; Equipment Design ; Pressure

OBJECTIVE: To meet the treatment requirements for mitral regurgitation disease, this study designed a novel valve repair system and evaluated its hydrodynamic performance. METHODS: A mitral regurgitation model was created. The valve repair system was loaded onto the regurgitation model, and pulsatile flow tests and steady backflow leakage tests were conducted. RESULTS: The pulsatile flow test results indicated that the percentage of reflux after product implantation was lower than that before implantation under different concentric outputs and reverse pressures. The average cross-valve pressure difference after implantation was less than 5 mmHg. The steady backflow leakage test results showed that as the reverse pressure increased, the leakage amount of the valve repair system after implantation also increased. CONCLUSION The developed valve repair system exhibits excellent hydrodynamic performance, suggesting the feasibility of its application in the treatment of clinical mitral regurgitation.
Hydrodynamics ; Mitral Valve Insufficiency/surgery* ; Mitral Valve/surgery* ; Heart Valve Prosthesis ; Pulsatile Flow ; Heart Valve Prosthesis Implantation

Objective:To analyze the effects of adenoidectomy, tonsillectomy and tonsillectomy combined with adenoidectomy on obstructive sleep apnea children by computational fluid dynamics numerical simulation. Methods:A case of typical tonsil with adenoid hypertrophy was selected. Mimics 21.0 software was used to establish the original preoperative model, adenoidectomy, tonsillectomy and virtual surgical models of tonsillectomy combined adenoidectomy, and the computational fluid dynamics model of the upper airway was established by ANSYS 2019 R1 software, and then the pressure and velocity of the internal flow field of the CFD model were numerically simulated. Seven planes perpendicular to the flow trace were selected as the observation planes, including the cross section of the sinusostoma complex, the anterior end of the adenoid body, the narrowest cross section of the nasopharyngeal cavity, the pharyngostoma tube, the narrowest cross section of the oropharyngeal cavity, the lower pole of the tonsil and the glottis section. The comparison indexes included pressure, flow velocity and flow distribution. Results:Compared with the original model before operation, after the adenoids were removed only, the pressure drop between the section of the ostiomeatal complex and the section of the eustachian tube decreased, the high velocity peak at the anterior end of the adenoids disappeared, and the flow trace through the middle nasal canal increased. When only bilateral tonsils were removed, the pressure drop between the eustachian tube and the glottis slowed down and the flow velocity between the eustachian tube and the glottis slowed down. Combined tonsillar-adenoidectomy resulted in the most uniform pressure distribution, the most gentle pressure change and flow rate in the upper airway, and the most ignificant increase in airflow trace through the middle nasal canal among the three operations. Conclusion:Adenoidectomy, tonsillectomy and combined tonsillar adenoidectomy can make the airflow velocity and pressure of upper respiratory tract uniform to different degrees, but there are obvious differences in the specific anatomical location and degree. The application of CFD can intuitively predict the improvement of upper airway flow field in OSA children by different surgical methods, which helps clinicians to make surgical decision.
Humans ; Sleep Apnea, Obstructive/physiopathology* ; Adenoidectomy/methods* ; Tonsillectomy/methods* ; Child ; Hydrodynamics ; Adenoids/surgery* ; Computer Simulation ; Palatine Tonsil/surgery* ; Software

Objective: To analyze the impact of the sinonasal anatomic changes after endonasal endoscopic anterior skull base surgery on the nasal airflow and heating and humidification by computational fluid dynamics (CFD), and to explore the correlation between the postoperative CFD parameters and the subjective symptoms of the patients. Methods: The clinical data in the Rhinology Department of the First Affiliated Hospital of Zhengzhou University from 2016 to 2021 were retrospectively analyzed. The patients received the endoscopic resection of the anterior skull base tumor were selected as the case group, and the adults whose CT scans had no sinonasal abnormalities were chosen as the control group. The CFD simulation was performed on the sinonasal models after reconstructed from the patients' sinus CT images during the post-surgical follow-up. All the patients were asked to complete the Empty Nose Syndrome 6-Item Questionnaire (ENS6Q) to assess the subjective symptoms. The comparison between two independent groups and the correlation analysis were carried out by using the Mann-Whitney U test and the Spearman correlation test in the SPSS 26.0 software. Results: Nineteen patients (including 8 males and 11 females, from 22 to 67 years old) in the case group and 2 patients (a male of 38 years old and a female of 45 years old) in the control group were enrolled in this study. After the anterior skull base surgery, the high-speed airflow moved to the upper part of the nasal cavity, and the lowest temperature shifted upwards on the choana. Comparing with the control group, the ratio of nasal mucosal surface area to nasal ventilation volume in the case group decreased [0.41 (0.40, 0.41) mm^-1 vs 0.32 (0.30, 0.38) mm^-1; Z=-2.04, P=0.041], the air flow in the upper and middle part of the nasal cavity increased [61.14 (59.78, 62.51)% vs 78.07 (76.22, 94.43)%; Z=-2.28, P=0.023], the nasal resistance decreased [0.024 (0.022, 0.026) Pa·s/ml vs 0.016 (0.009, 0.018) Pa·s/ml; Z=-2.29, P=0.022], the lowest temperature in the middle of the nasal cavity decreased [28.29 (27.23, 29.35)℃ vs 25.06 (24.07, 25.50)℃; Z=-2.28, P=0.023], the nasal heating efficiency decreased [98.74 (97.95, 99.52)% vs 82.16 (80.24, 86.91)%; Z=-2.28, P=0.023], the lowest relative humidity decreased [(79.62 (76.55, 82.69)% vs 73.28 (71.27, 75.05)%; Z=-2.28, P=0.023], and the nasal humidification efficiency decreased [99.50 (97.69, 101.30)% vs 86.09 (79.33, 87.16)%; Z=-2.28, P=0.023]. The ENS6Q total scores of all patients in the case group were less than 11 points. There was a moderate negative correlation between the proportion of the inferior airflow in the post-surgical nasal cavity negatively and the ENS6Q total scores (r_s=-0.50, P=0.029). Conclusions: The sinonasal anatomic changes after the endoscopic anterior skull base surgery alter the nasal airflow patterns, reducing the efficiency of nasal heating and humidification. However, the post-surgical occurrence tendency of the empty nose syndrome is weak.
Adult ; Humans ; Male ; Female ; Young Adult ; Middle Aged ; Aged ; Retrospective Studies ; Hydrodynamics ; Air Conditioning ; Nose ; Nasal Cavity ; Skull Base/surgery*

Objective:The nasal swell body（NSB） consists of the nasal septal cartilage, nasal bone, and swollen soft tissue, all of which are visible during endoscopic and imaging examinations. Although the function of the NSB remains uncertain, there is evidence to suggest that it plays a vital role in regulating nasal airflow and filtering inhaled air. Based on anatomical and histological evidence, it is hypothesized that the NSB is indispensable in these processes. This study aims to investigate the impact of NSB on nasal aerodynamics and the deposition of allergen particles under physiological conditions. Methods:The three-dimensional （3D） nasal models were reconstructed from computed tomography （CT） scans of the paranasal sinus and nasal cavity in 30 healthy adult volunteers from Northwest China, providing basis for the construction of models without NSB following virtual NSB-removal surgery. To analyze the distribution of airflow in the nasal cavity, nasal resistance, heating and humidification efficiency, and pollen particle deposition rate at various anatomical sites, we employed the computed fluid dynamics（CFD） method for numerical simulation and quantitative analysis. In addition, we created fully transparent segmented nasal cavity models through 3D printing, which were used to conduct bionic experiments to measure nasal resistance and allergen particle deposition. Results:①The average width and length of the NSB in healthy adults in Northwest China were （12.85±1.74） mm and （28.30±1.92） mm, respectively. ②After NSB removal, there was no significant change in total nasal resistance, and cross-sectional airflow velocity remained essentially unaltered except for a decrease in topical airflow velocity in the NSB plane. ③There was no discernible difference in the nasal heating and humidification function following the removal of the NSB; ④After NSB removal, the deposition fraction（DF） of Artemisia pollen in the nasal septum decreased, and the DFs post-and pre-NSB removal were（22.79±6.61）% vs （30.70±12.27）%, respectively; the DF in the lower airway increased, and the DFs post-and pre-NSB removal were（24.12±6.59）% vs （17.00±5.57）%, respectively. Conclusion:This study is the first to explore the effects of NSB on nasal airflow, heating and humidification, and allergen particle deposition in a healthy population. After NSB removal from the healthy nasal cavities: ①nasal airflow distribution was mildly altered while nasal resistance showed no significantly changed; ②nasal heating and humidification were not significantly changed; ③the nasal septum's ability to filter out Artemisia pollen was diminished, which could lead to increased deposition of Artemisia pollen in the lower airway.
Adult ; Humans ; Cross-Sectional Studies ; Nasal Cavity/surgery* ; Allergens ; Pollen ; Artemisia ; Hydrodynamics

Humans ; Diverticulum, Colon ; Fecal Impaction ; Hydrodynamics

In the process of occupational hazard management, computational fluid dynamics technology can be used to reflect the distribution pattern of occupational hazards in the production process, so as to quickly and accurately guide the formulation of occupational disease prevention and control programs. This paper summarizes and analyzes the current research results on the prevention and control of occupational hazards in workplaces through computational fluid dynamics technology, and describes the application of these research results in the process of occupational disease prevention and control. On this basis, this paper presents the problems and application limitations of existing research and points out the future key research directions, which are of great reference value for guiding further systematic and in-depth research on simulation, experimentation and management of occupational hazards that can cause occupational diseases.
Humans ; Hydrodynamics ; Computer Simulation ; Safety Management ; Occupational Diseases ; Technology

Currently, biomanufacturing technology and industry are receiving worldwide attention. However, there are still great challenges on bioprocess optimization and scale-up, including: lacing the process detection methods, which makes it difficult to meet the requirement of monitoring of key indicators and parameters; poor understanding of cell metabolism, which arouses problems to rationally achieve process optimization and regulation; the reactor environment is very different across the scales, resulting in low efficiency of stepwise scale-up. Considering the above key issues that need to be resolved, here we summarize the key technological innovations of the whole chain of fermentation process, i.e., real-time detection-dynamic regulation-rational scale-up, through case analysis. In the future, bioprocess design will be guided by a full lifecycle in-silico model integrating cellular physiology (spatiotemporal multiscale metabolic models) and fluid dynamics (CFD models). This will promote computer-aided design and development, accelerate the realization of large-scale intelligent production and serve to open a new era of green biomanufacturing.
Bioreactors ; Computer Simulation ; Fermentation ; Hydrodynamics

Computer Simulation ; Humans ; Hydrodynamics ; Nasal Cavity ; Nasal Obstruction ; Nose Diseases