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Combined effects of the nasal cycle and septal deviation on the relative humidity in the nasal cavity during inspiration

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JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY 2023年第7期37卷 3575-3581页

作者： Kim, Youn-Ji Jung, Yong Gi Kim, Hyo Yeol Na, Yang Konkuk Univ Dept Mech Engn Seoul 05029 South Korea Sungkyunkwan Univ Samsung Med Ctr Sch Med Dept Otorhinolaryngol Head & Neck Surg Seoul 06351 South Korea

In the presence of nasal septal deviation, the airflow can be skewed to the convex side of the airway. Asymmetry of the airflow partition can be aggravated if the decongestion phase of the nasal cycle occurs on the same side. This numerical study investigates the variation in the airflow partition over time during inspiration and the corresponding changes in relative humidity when septal deviation is combined with the nasal cycle. In the nasal cavities with a decongested convex side, the variation in the airflow partition ratio observed over time was larger than that in the nasal cavities not influenced by the nasal cycle. In addition, the decrease in the relative humidity of the convex side was larger, resulting in a relative humidity of as low as 76.3 %. Therefore, the convex side of the deviated cavity was more prone to nasal dryness under the influence of the nasal cycle.

关键词： computational fluid dynamics Nasal cycle Nasal septal deviation Nasopharynx Relative humidity

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Development and evaluation of a low-cost aerosol generator for experimental inhalation exposure to particulate matter

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INTERNATIONAL JOURNAL OF ENVIRONMENTAL SCIENCE AND TECHNOLOGY 2023年第11期20卷 12267-12284页

作者： Curbani, F. Mendes, R. M. A. dos Santos, J. G. Olivieri, D. N. Tadokoro, C. E. Univ Fed Espirito Santo Ctr Tecnol Dept Tecnol Ind Ave Fernando Ferrari 514 BR-29075910 Vitoria ES Brazil Univ Vila Velha Programa Posgrad Ecol Ecossistemas Vila Velha Brazil Univ Vila Velha Programa Posgrad Ciencia Anim Vila Velha Brazil Univ Vila Velha Programa Posgrad Ciencias Farmaceut Vila Velha Brazil Ctr Intelixencia Artificial Orense Spain Univ Vigo ESE Informat Orense Spain

To allow inhalation exposure studies, with control of particulate matter (PM) concentration/dose, a low-cost aerosol generator with real-time continual monitoring was developed and tested. This device can be used for comparing controlled laboratory experiments with resuspension of dry ambient PM or dry powders/particles to model atmospheric PM concentrations decoupling the PM sampling and the exposure. Dry powder disposed in a reservoir was resuspended using a generator that promoted the control of flow rates of clean air and containing-PM air for injection in a whole-body exposure chamber continuously monitored by a PM monitor allowing real-time control of PM concentration/dose. To quantify its ability to produce exposure conditions, the airflow dynamics within the exposure chamber with computational fluid dynamics was simulated. A study of PM size distribution and chemical composition was undertaken to compare the ambient and resuspended PM. Airflow circulation patterns show that no areas of stagnation were present;the exposure chamber allows enough dispersion and mixing for the exposure of the mice. While the aerosol generator produces more fine particles, which are a major health concern than coarse particles, it can adequately reproduce the atmosphere with target concentrations. The resuspension in aerosol generator does not cause significative variations in mass ratios of the chemical species that are similar in the ambient and resuspended PM. Overall, this low-cost exposure system can be used in different laboratories, making inhalation exposure techniques more accessible in order to replace more invasive/artificial exposure such as instillation techniques.

关键词： Animal models computational fluid dynamics Dose Exposure chamber Health effects Toxicological studies

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Research on vibration reduction of direct-drive piston pump based on porous variable diameter Helmholtz pulsation attenuator

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JOURNAL OF THE BRAZILIAN SOCIETY OF MECHANICAL SCIENCES AND ENGINEERING 2023年第1期45卷 1-15页

作者： Gong, Fei Nie, Songlin Huang, Yeqing Yin, Fanglong Hong, Ruidong Ji, Hui Beijing Univ Technol Beijing Key Lab Adv Mfg Technol Beijing 100124 Peoples R China Beijing Aerosp Technol Inst Beijing 100074 Peoples R China

Aiming at the vibration suppression and noise reduction of a direct-drive piston pump system, a novel porous variable diameter Helmholtz pulsation attenuator (abbr. PVDHPA) was developed. The vibration suppression mechanism of PVDHPA was analyzed, and the pressure and flow mathematical model was established. The fluid vibration energy absorption characteristics of PVDHPA with different structural parameters in the direct-drive pump system were analyzed by computational fluid dynamics simulation. The optimized damping hole and maximum diameter of the resonant cavity of the PVDHPA are 6.5 mm and 110 mm, respectively. Based on the custom-manufactured testing apparatus, the vibration absorption effect of the PVDHPA was verified. The test results show that the vibration response amplitude of the direct-drive pump is significantly reduced after the installation of PVDHPA, in which the vibration signals in the 200-400 Hz and 1000 Hz frequency bands are significantly suppressed, and the vibration impact in the vertical direction is most significantly weakened. Meanwhile, the foot vibration acceleration of the direct-drive pump system decreases by 7.4 dB(A). These researches provide an effective method for vibration and noise reduction of the direct-drive pump systems.

关键词： Direct-drive pump system Helmholtz pulsation attenuator computational fluid dynamics Vibration and noise

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Advancing OHL Rating Calculations: Modeling Mixed-Convective Cooling and Conductor Geometry

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IEEE TRANSACTIONS ON POWER DELIVERY 2023年第1期38卷 610-619页

作者： Kopsidas, Konstantinos Rahman, Shahnurriman Abdul AlAqil, Mohammed Abdulaziz Rolfo, Stefano Univ Manchester Dept EEE Manchester M13 9PL England Univ Sains Islam Malaysia Fac Engn & Built Environm Nilai 71800 Malaysia King Faisal Univ Elect Engn Dept Alahssa 31982 Saudi Arabia Sci & Technol Facil Council Sci Comp Dept Swindon SN2 1SZ England

The existing standard current-temperature calculations for overhead line (OHL) conductors have been adequate for conventional conductors and their operating temperatures. However, these calculations make assumptions and include simplifications about conductor geometry and aero-thermal-dynamics, introducing an error in the High-Temperature Low-Sag conductors operating temperatures. To quantify the error introduced by the shape of strands, the paper employs a Multi-Physics Finite Element Modeling approach that calculates the conjugate heat transfer for trapezoidal stranded OHL conductors. Furthermore, it proposes corrective equations to improve the accuracy of existing methods. The equations incorporate a new Nusselt number correlation for mixed convection and capture the surface area ignored by current calculations. The outer conductor geometry assumptions and the combined natural and forced convective cooling omission in the IEEE and CIGRE methods introduce an error at low (below 0.12 m/s) cross-flow wind speeds suggesting an underestimation of conductor temperature by up to 4%. In medium wind speeds, typically at 0.5 m/s-0.61 m/s, the standard methods overestimate the conductor temperature limiting its current-carrying capability. A 5% uprating for existing OHLs is potentially feasible, particularly for the trapezoidal stranded conductors, when removing the assumptions made in existing methods.

关键词： Conductors Standards Cooling Mathematical models Wind speed computational modeling Geometry computational fluid dynamics conjugate heat transfer mixed convection conductor temperature finite element modeling thermal rating overhead line conductors

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Comparison of Edge Vortices from Normal and Elliptic Flapping Flat Plates

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AIAA JOURNAL 2023年第3期61卷 1197-1209页

作者： Nair, Vivek Chintamani, Siddarth Dennis, Brian H. Univ Texas Arlington Arlington TX 76010 USA

computational analysis of elliptic and normal flat plate geometries, sized to wings of small fliers and in a two-dimensional plunging-pitching-flapping motion resulting in hover, is conducted to investigate circulation growth at the leading-edge vortex (LEV) and trailing-edge vortex (TEV). The models are sized to the same aspect ratio, and a Reynolds number of 225 is chosen as it is similar to that observed in small fliers in hover. Results show similar LEV growth and lift production trends for both cases but with differing energy flux mechanisms. A vorticity transport analysis is done to quantify these energy fluxes. The LEV growth and shearing is closely related to the TEV growth and shearing, and the plunging-pitching profile, while the geometry plays a role in the magnitude of vortex creation and intensity of spanwise fluxes only.

关键词： Vortex Structure computational fluid dynamics Vortex Shedding Flapping Trailing Edge Vortices TEV Leading Edge Vortices LEV Hover Low Reynolds Number Flat Plate

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Multiphase Radiation Characteristics of a Laboratory-Scale Pulverized Coal Flame

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2023年第2期37卷 477-490页

作者： Wang, Chaojun He, Di He, Boshu Kuang, Yucheng Ren, Qiang Beijing Jiaotong Univ Inst Combust & Thermal Syst Sch Mech Elect & Control Engn Beijing 100044 Peoples R China Beijing Promin Publishing Co Ltd Beijing 100083 Peoples R China

A coal combustion solver with detailed multiphase radiation modeling has been developed and applied during the simulation of a laboratory-scale coal flame in this work. The carrier gas is modeled by the Eulerian equation while the coal particles are tracked in a Lagrangian framework. Radiative heat sources are fed back to the energy equations of both carrier gases and dispersed particles. The spectral properties for both gases and coal particles are either calculated by the full-spectrum k-distribution (FSK) method or considered to be gray, and the radiative transfer equation is solved by the spherical harmonics (PN) method at different orders. High-fidelity radiation effects on temperature, liftoff height, combustion products, and coal burnout for the target flame are investigated. It is found that radiation has a significant cooling effect on the flame. Involving radiation during the simulation of target flame makes both liftoff height and coal burnout closer to the experimental measurements, and also alters the combustion productions. Results also show that, considering both accuracy and efficiency, the P1 solver combined with either FSK method or gray method should be acceptable an alternative for multiphase radiation modeling of target flame.

关键词： Pulverized Coal Catalytic Combustion computational fluid dynamics Radiative Heat Transfer Calculations Multiphase Heat Transfer

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Performance improvement of forward-curved impeller with an adequate outlet swirl using in centrifugal pump as turbine

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RENEWABLE ENERGY 2023年第1期204卷 67-76页

作者： Wang, Tao Xiang, Ru Yu, He Zhou, Min Xihua Univ Key Lab Fluid & Power Machinery Minist Educ Chengdu 610039 Sichuan Peoples R China Xihua Univ Key Lab Fluid Machinery & Engn Chengdu 610039 Sichuan Peoples R China

Pump as turbine (PAT) is a type of economical energy recovery device that is widely used in micro-hydropower plants and energy recovery. A special impeller with forward-curved blades can dramatically improve the PAT's performance relative to an original impeller with backward-curved blades because the inlet angle created by the former more effectively matches volute outlet flow. The blade outlet angle is another important factor in energy conversion. To investigate the effects of blade outlet angle on the performance of a special impeller, four outlet velocity moments were chosen according to the same inlet velocity moment value vu(1)r(1) (0.02vu(1)r(1), 0, -0.02vu(1)r(1),-0.04vu(1)r(1), were used). Four special impellers with different blade outlet angles were modeled and simulated via verified computational fluid dynamics. The results show that, the highest efficiency among PATs at - 0.02vu(1)r(1) was higher than that at 0.02vu(1)r(1) by 1.46%. A suitable negative outlet velocity moment also helps eliminate swirl at the impeller outlet caused by the asymmetric inlet velocity moment and helps reduce the formation of vortex in the draft tube. This further decreases hydraulic loss and improves the operating stability of PAT. This paper presents a method for determining the blade outlet angle of the special impeller of PAT.

关键词： Pump as turbine Special impeller Blade outlet angle Velocity moment computational fluid dynamics

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Experimental and computational Analysis of Surgical Mask Effectiveness Against COVID-19 in Indoor Environment

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AEROSOL AND AIR QUALITY RESEARCH 2023年第11期23卷 1-15页

作者： Suen, Chin Yan Kwok, Helen Hoi Ling Tsui, Yuk Hang Lui, Ka Hei Leung, Hong Hang Lam, Ka Wo Hung, Karen Pik Shuen Kwan, Joseph Kai Cho Ho, Kin Fai Hong Kong Univ Sci & Technol Div Environm & Sustainabil Hong Kong Peoples R China Hong Kong Univ Sci & Technol Inst Environm Hong Kong Peoples R China Hong Kong Univ Sci & Technol Dept Math Hong Kong Peoples R China Hong Kong Univ Sci & Technol Dept Comp Sci & Engn Hong Kong Peoples R China Hong Kong Univ Sci & Technol Dept Chem & Biol Engn Hong Kong Peoples R China Chinese Univ Hong Kong Jockey Club Sch Publ Hlth & Primary Care Hong Kong Peoples R China

An experiment coupled with a computational analysis was conducted to investigate the effectiveness of surgical masks, which include KF94 and ASTM Level 1, in an indoor environment. The KF94 mask sample shows the highest filtration efficiency (99.9%) in the analysis. The simulation is consistent with the experimental results as the concentration of sodium chloride (NaCl) droplets is < 4% on average in the room. The ultraviolet-C (UVC) irradiation and dry heating samples are shown to retain the highest filtration efficiencies (> 97%) after 3 disinfection treatment cycles. All methods (boiling, steaming, ethanol treatment, and dry heating) effectively reduce the S. aureus load by 99.99%. The UVC irradiation shows exposure to 450 mu W cm(-2) for 10 minutes can effectively eliminate all S. aureus on the mask materials. Simulation shows the reduction in overall NaCl and carbon dioxide (CO2) levels is directly proportional to the filtration efficiency and the effectiveness of reused masks is also directly proportional to the filtration efficiency. The proxy indicator (CO2) for aerosol particles demonstrates that very fine respiratory droplets can penetrate the mask after reaching a steady state. The CO2 concentration increase shows that aerosol particles are accumulated under adequate ventilation and further pose the risk of infection. The NaCl droplets (2%) simulation shows that respiratory droplets have infiltrated the mask, but the mask demonstrates a higher ability to block the NaCl droplets and prevent their penetration. The findings suggest a need to revise the existing regulation of the control policy.

关键词： Surgical mask Disinfection methods COVID-19 computational fluid dynamics Indoor air quality

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Simulation of circular pipe flow of thixotropic cemented tailings pastes

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CHEMICAL ENGINEERING RESEARCH & DESIGN 2023年第1期196卷 671-684页

作者： Zhang, Lianfu Wang, Hongjiang Wu, Aixiang Yang, Ke Kong, Peng Anhui Univ Sci & Technol Anhui Engn Res Ctr Exploitat & Utilizat Closed Aba Huainan 232001 Peoples R China Hefei Comprehens Natl Sci Ctr Inst Energy Hefei 230031 Peoples R China Anhui Univ Sci & Technol Sch Min Engn Huainan 232001 Peoples R China Univ Sci & Technol Beijing Sch Civil & Resource Engn Beijing 100083 Peoples R China

Cemented tailings pastes (CTPs) exhibit complex thixotropic behaviors, which considerably affect the accurate prediction of pressure drop in circular pipe transport. In this work, the thixotropy of CTPs is incorporated into the numerical simulation via a constitutive thixotropic model. The analytical solution of the velocity profile across the pipe based on the equilibrium rheological model is presented. Comparisons indicate that the Bingham model cannot accurately characterize the flow behaviors of CTPs. It also overestimates the pressure drop in the circular pipe. Moreover, the pressure drop predicted by the novel equilibrium model is overestimated because of thixotropy. A peak of the structural parameter can be observed near the edge of the plug region, which highly influences shear rate distribution. The effects of solids content and flow rate on pressure drop are analyzed. In summary, thixotropy should be considered in the circular pipe flow simulation of CTPs.& COPY;2023 Institution of Chemical Engineers. Published by Elsevier Ltd. All rights reserved.

关键词： Cemented tailings pastes Thixotropy computational fluid dynamics Pipe flow Pressure drop

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Influence of impingement flows with sand particles on the barrier properties of organic coatings

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JOURNAL OF COATINGS TECHNOLOGY AND RESEARCH 2023年第4期20卷 1235-1255页

作者： Vedadi, Amin Estevadeordal, Jordi Wang, Xinnan Rao, Jiajia Wang, Yechun North Dakota State Univ NDSU Dept Mech Engn 2490POB 6050 Fargo ND 58108 USA North Dakota State Univ NDSU Dept Plant Sci 7670POB 6050 Fargo ND 58108 USA

The installations of offshore wind farms, especially the type with monopile structures, increase the number of suspended particles in the surrounding area. The offshore wind structures are usually coated with several layers of coatings, including a thin layer of organic coating as a topcoat. In this study, we aim to investigate the influence of the stresses on the organic coatings due to the kinetic energy of the suspended sand particles. To accomplish the goal, impingement flow jets with particles were applied on coated steel samples for a week in a lab-scale impingement chamber. The working fluid for the experiments was 3.5 wt% NaCl solution with 1 wt% suspended sand particles. Electrochemical impedance spectroscopy (EIS) was conducted to monitor the degradation of organic coatings while exposed to the impingement flow. computational fluid dynamics (CFD) modeling was utilized to calculate the magnitude of the applied fluid stresses on the coatings. Thermodynamics of electrochemical reactions and the activation theories were utilized to compare with the electrochemical parameters. It was concluded that for the lowest flow rate (Q(1) = 6.31 cm(3)/s), the added sand particles started to show destructive influence after the first three days of exposure. As the flow rate increased, the destructive influence of sand particles on coating samples appeared earlier at the beginning of the exposure, and the elements of equivalent circuit model showed larger difference between coatings exposed to pure NaCl solution and those exposed to solution with sand particles. For the highest flow rate (Q(3) = 18.93 cm(3)/s), the destructive influence of sand particles was significant, indicating that for the particulate flows with the velocity of 1 m/s, which is the regular velocity of the underwater zone in shallow sea regions (with a depth of 30 m), the momentum impact of the sand particles plays a vital role in the degradation of the organic coatings.

关键词： Organic coatings Offshore wind structures Impingement particulate flow Electrochemical impedance spectroscopy computational fluid dynamics

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