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Numerical analysis of dry heat transfer in textiles and clothing microclimate

TEXTILE RESEARCH JOURNAL 2025年

作者： Gao, Zenghui Zheng, Dongming Guo, Kai Zou, Haochen Ding, Wensheng Du, Zhaoqun Xue, Jingli Jin, Guang Mou, Huangbo Donghua Univ Coll Text Key Lab Text Sci & Technol Minist Educ Shanghai Peoples R China Jiangxi Gen Inst Testing & Certificat Inst Text Testing & Certificat Nanchang Peoples R China Consinee Grp Co Ltd Ningbo Zhejiang Peoples R China

The computational fluid dynamics approach has been widely applied to explore the comfort level of human clothing. In many studies, the human limbs and trunk are treated as a uniform cylinder, yet there is a failure to consider the uniformity of airflow velocity and temperature on the surface of clothing. This poses challenges for the testing of cylindrical fabric thermal and moisture resistance to assess clothing comfort. In this study, a 2D heat transfer model for porous textiles under different airflow and temperature conditions was established. Then, a comparative analysis was conducted of three air supply methods. The results show that the wind speed difference rates generated on the surface of the clothing by these three air supply methods were 83.3%, 65.1%, and 1.9%, respectively. To ensure that the wind speed on the surface of the clothing is as uniform as possible, method 3 was adopted to establish the wind field. In this study, the combined influences of thermal conduction, natural convection, and forced convection were incorporated to investigate the distribution of temperature and wind fields within the model, as well as the changes in clothing performance under various environmental conditions. Additionally, the microclimate between the skin and clothing directly affects human comfort. Therefore, in this study, heat transfer phenomena within the microclimate were also explored under different environmental conditions. The model in this paper is intended to provide an effective and accurate method for cylindrical fabric thermal and moisture resistance testing, to study the comfort of clothing.

关键词： Heat transfer computational fluid dynamics simulation clothing microclimate heat flux

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Development of applicator to deliver hydrogel precursor powder for esophageal stricture prevention after endoscopic submucosal dissection

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CHEMICAL ENGINEERING JOURNAL 2024年 500卷

作者： Fujiyabu, Takeshi Qi, Pan Yoshie, Kenichi Fujisawa, Ayano Tsuji, Yosuke Chandel, Arvind Kumar Singh Madhavikutty, Athira Sreedevi Inagaki, Natsuko F. Ohta, Seiichi Fujishiro, Mitsuhiro Ito, Taichi Univ Tokyo Grad Sch Engn Dept Chem Syst Engn 7-3-1 HongoBunkyo Ku Tokyo 1138656 Japan Univ Tokyo Ctr Dis Biol & Integrat Med Grad Sch Med Hongo 7-3-1Bunkyo Ku Tokyo 1130033 Japan Prod Innovat Assoc 2-11-16 YayoiBunkyo Ku Tokyo 1138656 Japan Univ Tokyo Grad Sch Engn Dept Bioengn 7-3-1 HongoBunkyo Ku Tokyo 1138656 Japan Univ Tokyo Grad Sch Med Dept Gastroenterol 7-3-1 HongoBunkyo Ku Tokyo 1138656 Japan Univ Tokyo Inst Engn Innovat Grad Sch Engn 7-3-1 HongoBunkyo Ku Tokyo 1138656 Japan

Esophageal stricture can be an adverse event following endoscopic submucosal dissection (ESD). Although particle-shaped materials could prevent post-ESD esophageal strictures, no applicator can efficiently deliver them to the ESD wound site. In this study, we developed an applicator to endoscopically deliver powders by combining polytetrafluoroethylene (PTFE) tubes and five types of catheter-tip nozzles with different structures fabricated using a 3D printer. The applicator with a T3S4 nozzle, with three and four holes on the tip and side, respectively, achieved lateral powder delivery from the endoscope catheter tip. The adhesion percentage to the ESD wound site, estimated using the esophagus mimicking model setup with tubes and wetted laboratory wipes, increased from 25 % (without the nozzle) to 55 % (with the T3S4 nozzle). In the computational fluid dynamics (CFD) simulation without a nozzle, the powder particles went straight, and hardly adhered to the ESD wound site. By contrast, the CFD simulation with the optimized T3S4 nozzle predicted that the adhesion percentage would increase by up to 52 %. Optimization of the axial position of the catheter affected the powder delivery efficiency, while optimizing the radial position and angle affected the homogeneity of powder delivery. An in vivo porcine ESD model using the developed applicator confirmed efficient and homogeneous powder delivery to the ESD wound site. These results suggest that the powder applicator development and CFD simulations are effective in treatments using endoscopic powder delivery.

关键词： Endoscopic submucosal dissection Esophageal stricture prevention Powder delivery Powder applicator development computational fluid dynamics simulation

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Substrate engineering-enhanced low-temperature NOx and CO removal by Co1Mn2Ox@CuO/copper mesh monolithic catalyst

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JOURNAL OF COLLOID AND INTERFACE SCIENCE 2025年 697卷 137936页

作者： Ma, Jianing Gao, Yanshan Gui, Rongrong Ren, Penghui Su, Liyao Wei, Jiaqi Wang, Qiang Beijing Forestry Univ Coll Environm Sci & Engn Beijing 100083 Peoples R China Beijing Forestry Univ State Key Lab Efficient Prod Forest Resources Beijing 100083 Peoples R China

This paper addresses the challenges of simultaneously removing nitrogen oxides (NOx) and carbon monoxide (CO) from industrial flue gas at low temperatures. A highly efficient Co1Mn2Ox@CuO/copper mesh (CM) monolithic catalyst with higher oxygen vacancies was developed by growing Cu(OH)2 nanorods in-situ on a copper mesh and subsequently synthesizing via a hydrothermal method. Experimental results show that the Co1Mn2Ox@CuO/CM catalyst can achieve 99.7 % NOx conversion and 99.4 % CO conversion at 160 degrees C, with strong resistance to H2O and SO2 and outstanding long-term stability. Characterization results demonstrated that the excellent catalytic performance can be ascribed to the presence of abundant high-valent Co3+, Mn4+, and Cu2+ species, an increased number of reducible species, more acidic sites, and a higher concentration of oxygen vacancies. The interaction between ammonia-based selective catalytic reduction (NH3-SCR) and CO oxidation reactions revealed that NH3 primarily inhibited CO oxidation, whereas CO had no significant inhibitory effect on NH3-SCR. Additionally, this study explored the factors contributing to the enhanced water resistance and the underlying mechanisms of both NH3-SCR and CO oxidation reactions using in-situ diffuse reflectance infrared transform spectroscopy (in-situ DRIFTS). In terms of application, computational fluid dynamics (CFD) simulations demonstrated that the copper mesh-based monolithic catalyst provided better heat distribution, preventing partial deactivation and contributed to the improvement of catalytic activity. This research provides an efficient solution for industrial flue gas treatment and highlights its potential for environmental applications.

关键词： Simultaneous removal CO oxidation Monolithic bifunctional catalysts Copper substrate computational fluid dynamics simulation

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Powered Low-Speed Experimental Aerodynamic Investigation of an Over-Wing-Mounted Nacelle Configuration

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JOURNAL OF AIRCRAFT 2024年第2期61卷 415-424页

作者： Silva, Vinicius T. Lundbladh, Anders Xisto, Carlos Milten, Petter Jonsson, Isak GKN Aerosp S-46181 Trollhattan Sweden Chalmers Univ Technol S-41258 Gothenburg Sweden

Over-wing integration of ultrahigh bypass turbofan engines can be a solution for next-generation commercial transport aircraft since it eliminates the ground clearance issue and it has the potential to reduce ground noise due to acoustic shielding. Moreover, a unique characteristic of this installation type is the powered lift benefit at low-speed flight conditions. This paper aims to experimentally investigate the effect of the engine power setting on the low-speed aerodynamic performance of an over-wing-mounted nacelle configuration comprising a conventional tube-and-wing layout. Thus, low-speed wind tunnel tests were performed for a half-span powered scale model of the aforementioned configuration. The effect of the engine power setting on the wing lift and spanwise pressure distributions was investigated. The experiments were carried out for angles of attack varying from 0 to 6 degrees and inlet mass flow ratios up to 2.4. The results were used to validate computational fluid dynamics simulations conducted for the same wind tunnel conditions. It has been shown that a significant powered lift benefit can be achieved for the studied configuration, without a penalty in the net propulsive force and that the lift increases linearly with the inlet mass flow ratio. Furthermore, it was observed that the engine power setting largely influences the pressure distributions along the wing, especially at the spanwise sections closer to the nacelle. The low-momentum zone created upstream of the engine at high power settings reduces the pressure at the wing's upper surface, which is the main factor responsible for the increased lift. By taking advantage of such behavior, drag can potentially be reduced at takeoff and climb due to a lower flap setting required for the same lift.

关键词： computational fluid dynamics simulation Wind Tunnel Tests Airframe/Propulsion Integration Applied Aerodynamics Over-wing Mounted Nacelles Low Speed Powered Testing

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Corner Vortex Structures Within Recirculation Zones of Confined Bluff-Body Flows

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AIAA JOURNAL 2024年第8期62卷 2900-2911页

作者： Squeo, Joseph N. Sykes, Joshua P. Comer, Adam L. Gallagher, Timothy P. Rankin, Brent A. Innovat Sci Solut Inc Dayton OH 45459 USA AF Res Lab Edwards AFB CA 93524 USA AF Res Lab Wright Patterson AFB OH 45433 USA

The vortical structures of recirculation zones in turbulent nonreacting and premixed reacting flows around confined equilateral-triangle bluff bodies are investigated using large-eddy simulations. A three-dimensional flow structure is observed within the recirculation zones of reacting and nonreacting cases;the structure includes both the "spanwise" vortices that extend the length of the recirculation zone and "corner vortex structures" that are situated adjacent to the bluff-body trailing edge and spanwise walls. The corner vortex structures enhance the mixing and residence times of fluid inside the recirculation zone. fluid is circulated between the spanwise vortices and corner vortex structures. Corner vortex structures always appear downstream (relative to the local flow) of the boundary-layer separation location on the spanwise walls within the recirculation zone, and they are absent when boundary-layer formation on the spanwise walls is prevented. Laminar boundary-layer theory predicts the boundary-layer separation locations within similar to 12% of the calculated values from the large-eddy simulations in all but one case. These results suggest that 1) boundary-layer separation on the spanwise walls is a necessary condition for the formation of corner vortex structures, and 2) boundary-layer separation on the spanwise walls is caused by an adverse pressure gradient in the recirculation zone.

关键词： Vortex Structure Boundary Layer Separation Non Reacting Flow computational fluid dynamics simulation Adverse Pressure Gradient Combustion Chambers Combustors Lean Premixed Combustor

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Shape Optimization of Pin-Fins by Free-Form Deformation and Active Learning Surrogate Model

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JOURNAL OF THERMOPHYSICS AND HEAT TRANSFER 2023年第2期37卷 448-456页

作者： Yang, Fan Chen, Zhaolin Nanjing Univ Aeronaut & Astronaut Nanjing 210016 Peoples R China

The shapes of pin-fins play an essential role in enhancing overall and local forced convective heat removal. This study presents a new design optimization scheme based on the free shape deformation method, which gives rise to nonuniform pin-fin shapes depending on local flow structures interacting with each local pin-fin. The grid of pin-fins is embedded in a parameter space formed by basic function and control points. By moving the position of the control points, the shapes of the pin-fins and the neighborhood grid are deformed during optimization. The optimization objective function is the heat transfer coefficient of the pin-fin arrays at a limited pressure drop to ensure cycle efficiency. In addition, to reduce the computational resources, the active learning surrogate model for constraint global optimization is adopted, which is combined with computationally expensive computational fluid dynamics simulations. To exemplify the effectiveness of the proposed method on optimizing the pin-fin shape, two-dimensional pin-fins in inline arrangements are considered. Finally, an improvement in the heat transfer of 33.4% is achieved as compared to the baseline. Therefore, the proposed method of pin-fin optimization is effective in improving thermal performance.

关键词： Numerical Modeling Heat Transfer Coefficients computational fluid dynamics simulation Thermal Performance Heat Sinks Shape Optimization Sensitivity Analysis Finite Volume Method Multi Objective Genetic Algorithm Probability Density Functions

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Numerical simulation of flow field characteristics and pollutant transport under different ventilation modes

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ENVIRONMENTAL fluid MECHANICS 2024年第6期24卷 1369-1386页

作者： Chang, Xiaoke Chai, Junrui Chen, Xingzhou Bian, Minghan Xian Univ Sci & Technol Sch Architecture & Civil Engn Xian 710054 Peoples R China Xian Univ Technol State Key Lab Base Eco Hydraul Engn Northwest Arid Xian 710048 Peoples R China

A large amount of pollutants are generated during tunnel blasting construction, which seriously endangers the life and health of construction personnel. Reasonable design and resolution of ventilation issues have become the key to ensure the safety of engineering construction. This study established a ventilation simulation engineering during tunnel construction using numerical methods of computational fluid dynamics. The mechanism of the turbulent air flow generated by the restriction of air jet and wall is proved by simulating the distribution of the flow field in the tunnel under various ventilation modes. The retarding effect of vortex conducted by air flow and pollutant transport diffusion mechanism resulted in two peak distributions of pollutants. The discharge of harmful gases has both the transport effect of the main airflow and the diffusion effect of the turbulent airflow. Jet fans can effectively accelerate the dispersion of pollutants in the vortex zone. The time cost law of ventilation saving under different ventilation modes is found through comparison. On this basis, a new annular ventilation method combining longitudinal and transverse ventilation in tunnels is proposed. Not only can it greatly save ventilation time and costs, but it also provides a very friendly solution to the residual pollutants in the vicinity of the working face. The research work of this project provides important reference and guidance value for practical engineering. The distribution law of air flow field and the mechanism of pollutant transport and diffusion in the tunnel are revealed.A new type of ventilation mode is constructed based on numerical *** advantages and disadvantages of different ventilation modes are analyzed and compared to provide guidance for practical projects.

关键词： Tunnel engineering computational fluid dynamics simulation Ventilation modes fluid field Concentration field

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The Effect of Inlet Angle Structure of Concave and Convex Plate on Internal Flow Characteristics of Alkaline Electrolyzer

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Frontiers in Heat and Mass Transfer 2024年第3期22卷 855-868页

作者： Bo Hui Shengneng Zhu Sijun Su Wenjuan Li Key Laboratory of Low-Grade Energy Utilization Technologies and Systems Ministry of EducationSchool of Energy and Power EngineeringChongqing UniversityChongqing400044China Lanzhou Lanshi Group Co. Ltd.Lanzhou730300China

The structure of the concave-convex plates has proven to be crucial in optimizing the internal flow characteristics of the electrolyzer for hydrogen *** paper investigates the impact of the gradual expansion angle of the inlet channel on the internal flow field of alkaline *** flow distribution characteristics of concave-convex plates with different inlet angle structures in the electrolytic cell is ***,the system with internal heat source is *** results indicate that a moderate gradual expansion angle is beneficial for enhancing fluid ***,an excessively large gradual expansion angle may lead to adverse reflux phenomena,reducing the overall performance of the electrolytic cell.

关键词： Inlet angle structure vortex motion distribution uniformity computational fluid dynamics simulation

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PRESSURE GRADIENT COMPUTATION FOR FOAMS WITH DIFFERENT GEOMETRIC PROPERTIES: BASED ON ANN AND SVR MACHINE LEARNING MODEL AND TRAINED BY CFD simulationS

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JOURNAL OF POROUS MEDIA 2023年第9期26卷 49-76页

作者： Jafarizadeh, Azadeh Ahmadzadeh, MohammadAli Mahmoudzadeh, Sajad Panjepour, Masoud Isfahan Univ Technol Esfahan Iran Univ Tehran Tehran Iran

In this research work, a combination of computational fluid dynamics (CFD) simulation and artificial intelligence (AI) methods are conducted to study the effects of geometric properties of aluminum foams on airflow and to compute and predict pressure gradients in foams with such varied geometric parameters as porosity (65-90%) and pore diameter (200-2000 mu m). The 3D foam structures are created by the Laguerre-Voronoi tessellations method. Based on the CFD results, pressure gradient for 114 different foams can be calculated in terms of inlet flow velocity (in the range 0.1-8 m/s). Foam pressure gradient is found to increase with increasing inlet flow velocity but with decreasing pore diameter and porosity. Comparisons reveal that the results obtained in the present study for pressure gradient are consistent with the data reported in the literature. It is, therefore, concluded that CFD simulation is a useful tool for pressure gradient estimation in a variety of foam types. Unique simulations are, however, needed each time foam structural properties change, which entails significant increases in the associated computation costs. This drawback may, nonetheless, be at least partially addressed by taking advantage of soft computing methods such as machine learning (ML). Artificial neural network (ANN) and support vector regression (SVR) as subsets of AI are designed (models with input variables inlet velocity and the foam structural parameters: porosity, pore diameter, and strut diameter) and trained using CFD results to predict pressure gradients in a large number of foams. When applied to new foam samples, the ML models exhibit an acceptable performance in predicting pressure gradients. Using such provisions, the method can be effectively used for predicting pressure gradient in various porous media at minimum computation costs.

关键词： foam structural parameters fluid flow predicting pressure gradient computational fluid dynamics simulation machine learning models artificial neural network support vector regression

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Bayesian Gappy Proper Orthogonal Decomposition for Aerodynamic Data Fusion

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AIAA JOURNAL 2023年第9期61卷 4032-4044页

作者： Bertram, Anna Bekemeyer, Philipp Held, Matthias German Aerosp Ctr DLR Inst Aerodynam & Flow Technol D-38108 Braunschweig Germany Airbus Operat GmbH Aerodynam Modelling Loads Aircraft Aerodynam D-28199 Bremen Germany

During the development of an aircraft, a multitude of aerodynamic data are required for different flight conditions throughout the flight envelope. Nowadays, a large portion of these data are routinely acquired by computational fluid dynamics simulations. However, due to modeling and convergence issues especially for extreme flight conditions, numerical data cannot be reliably generated for the entire flight envelope yet. Hence, numerical data are complemented by data from wind tunnel experiments and flight testing. However, the data from these different sources will always show some discrepancies to deal with. Data fusion methods aim at combining the individual strengths and weaknesses of data from different sources in order to provide a consistent data set for the entire parameter domain. In this work we propose an extension to the well-established Gappy proper orthogonal decomposition technique by reformulating the least-squares problem as a regression task. A Bayesian perspective is imposed to account for uncertainties during the data fusion process. This involves a kernelized regression formulation that also addresses the problem of linearity imposed by the dimensionality reduction method and therefore adds more flexibility to the approach. The performance and robustness of the approach is demonstrated investigating an industrially relevant, large-scale aircraft test case fusing high-quality experimental and numerical data. Compared to the established Gappy POD approach, the new method shows a significantly improved agreement with the observed wind tunnel data for the investigated test case. In addition, the new approach enables to provide credible bounds for the fused result, which serve as an indicator for the associated uncertainty.

关键词： Aerodynamic Characteristics computational fluid dynamics simulation European Transonic Windtunnel Data Analysis Gaussian Process Regression Pressure Coefficient Data Fusion Surrogate Model Bayesian Approach

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