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Experimental analysis and simulation of a centrifugal jet fan for impulse ventilation systems

JOURNAL OF BUILDING ENGINEERING 2022年 57卷

作者： Xue, Yu Li, Xiaomeng Li, Ning Zheng, Shu Wang, Zhichao Dalian Univ Technol Sch Civil Engn Dalian 116000 Peoples R China State Key Lab Bldg Safety & Built Environm Beijing 100013 Peoples R China China Acad Bldg Res Beijing 100013 Peoples R China

Centrifugal jet fans are usually used to stir evenly, remove local airflow blind spots, and improve air quality. They are widely used in HAVC systems of garage buildings recently. However, there are few in-depth studies on its modeling methods, and even the experimental verification of the most basic centrifugal jet fan simulation model has not been fully demonstrated. This paper combines experimental verification with numerical simulation to investigate the appropriate modeling method and jet characteristics of centrifugal jet fans for impulse ventilation systems. Experimental data showed that the air volume of each nozzle of the centrifugal jet fan was different, and that even outlet velocity of a single nozzle was not uniform. Velocity decreased slightly in the jet core area and then decreased gradually until it approached the ambient velocity, while the amount of air entrained by the jet was approximately linear with respect to the jet range. In addition, the design key points and methods of impulse ventilation systems was sum-marized. CFD was used to simulate the flow field of centrifugal jet fans. Two modeling strategies, involving accurate boundary conditions based on experimental data, and simplified velocity boundary conditions, were used, and displayed differing characteristics. When designers focus on the coverage range of jet fans and the velocity distribution at the far-field, or the operation performance of jet fans in HAVC systems, the simplified velocity boundary conditions can be used. When the aim is to study and optimize nozzle, an accurate model and boundary conditions should be utilized. System Coefficient rate

关键词： Centrifugal jet fan Impulse ventilation system computational fluid dynamics simulation Modeling method Design method

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Large-scale single-cell encapsulation in microgels through metastable droplet-templating combined with microfluidic-integration

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BIOFABRICATION 2022年第3期14卷 035015-035015页

作者： Zhang, Haoyue Zhang, Liyuan An, Chuanfeng Zhang, Yang Shao, Fei Gao, Yijie Zhang, Yonghao Li, Hanting Zhang, Yujie Ren, Changle Sun, Kai He, Wei Cheng, Fang Wang, Huanan Weitz, David A. Dalian Univ Technol Sch Bioengn State Key Lab Fine Chem Dalian 116024 Peoples R China Harvard Univ John A Paulson Sch Engn & Appl Sci Cambridge MA 02138 USA Chinese Univ Hong Kong Cent Lab Longgang Dist Peoples Hosp Shenzhen Shenzhen 518172 Peoples R China Chinese Univ Hong Kong Affiliated Hosp 2 Shenzhen 518172 Peoples R China Shenzhen Univ Hlth Sci Ctr Sch Biomed Engn Guangdong Key Lab Biomed Measurements & Ultrasoun Shenzhen 518060 Peoples R China Shenzhen Univ Dept Biomed Engn Shenzhen 518037 Peoples R China Dalian Med Univ Dept Joint Surg Dalian Municipal Cent Hosp Dalian 116024 Peoples R China

Current techniques for the generation of cell-laden microgels are limited by numerous challenges, including poorly uncontrolled batch-to-batch variations, processes that are both labor- and time-consuming, the high expense of devices and reagents, and low production rates;this hampers the translation of laboratory findings to clinical applications. To address these challenges, we develop a droplet-based microfluidic strategy based on metastable droplet-templating and microchannel integration for the substantial large-scale production of single cell-laden alginate microgels. Specifically, we present a continuous processing method for microgel generation by introducing amphiphilic perfluoronated alcohols to obtain metastable emulsion droplets as sacrificial templates. In addition, to adapt to the metastable emulsion system, integrated microfluidic chips containing 80 drop-maker units are designed and optimized based on the computational fluid dynamics simulation. This strategy allows single cell encapsulation in microgels at a maximum production rate of 10 ml h(-1) of cell suspension while retaining cell viability and functionality. These results represent a significant advance toward using cell-laden microgels for clinical-relevant applications, including cell therapy, tissue regeneration and 3D bioprinting.

关键词： metastable emulsion integrated microfluidic chip cell-laden microgel scale up computational fluid dynamics simulation

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Electrochemical degradation of herbicide diuron on flow-through electrochemical reactor and CFD hydrodynamics simulation

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SEPARATION AND PURIFICATION TECHNOLOGY 2020年 251卷

作者： He, Yapeng Zhang, Panpan Huang, Hui Wang, Xue Chen, Buming Guo, Zhongcheng Lin, Haibo Kunming Univ Sci & Technol Fac Met & Energy Engn Kunming 650093 Yunnan Peoples R China Jilin Univ Coll Chem State Key Lab Inorgan Synth & Preparat Chem Changchun 130012 Peoples R China Met Electrode Mat Engn Technol Res Ctr Yunnan Pro Kunming 650106 Yunnan Peoples R China Kunming Hendera Sci & Technol Co Ltd Kunming 650106 Yunnan Peoples R China

An energy-efficient continuous flow-through electrochemical reactor (FT-ER) equipped with PbO2 filter anodes is designed and employed for electrochemical elimination towards herbicide diuron in the aquatic environment. Boosting performances, including substantially higher electrochemical mineralization kinetics and lower energy consumption, could be realized on the FT-ER compared with the traditional flow-by model. The effect of current density and flow rate on the degradation efficiency is also investigated. The glorious degradation kinetics could be ascribed to the large electrochemical surface area, strong generation power of reactive oxidants, and enhanced mass transfer process derived from the filter structure. Furthermore, we establish the computational fluid dynamics simulation to elucidate the dynamic flow behavior of the electrolyte, including fluid velocity and turbulent intensity distribution. The profound influence of FT-ER for the herbicide diuron removal stems from the homogenization of electrolyte flux and turbulence promoter of the filter structure. Finally, the continuous flow-through configuration exhibits excellent elimination performances, uniform fluid dynamics together with good stability. The filter anodes present a promising option for electrochemical treatment towards diverse organic pollutants in the aquatic environment and would be benefit to the evolution of cost-efficient electrochemical treatment techniques and reactors.

关键词： Flow-through electrochemical reactor Filter PbO2 anode Herbicide elimination Mass transfer kinetics computational fluid dynamics simulation

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Aerodynamic Behavior of a Floating Offshore Wind Turbine

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AIAA JOURNAL 2020年第9期58卷 3835-3847页

作者： Lienard, C. Boisard, R. Daudin, C. ONERA French Aerosp Lab Dept Aerodynam Aeroelast & Acoust F-92190 Meudon France

The flowfield around the rotor blades of a wind turbine is extremely complex due to the occurrence of several aerodynamic phenomena. It is all the more true for floating offshore wind turbines (FOWTs), for which the six rigid-body motions of the floating platform can induce blade-wake interactions. Therefore conventional numerical approaches for wind turbine applications, such as Blade Element Momentum Theory, may be questionable for an accurate prediction of floating wind turbine aerodynamic loads. Consequently, the current paper investigates the aerodynamic behavior of an FOWT subjected to several idealized prescribed motions, representative of a wave movement, based on computational fluid dynamics simulations. These results, obtained on the NREL 5-MW wind turbine, are compared with previous results found in the literature and analyzed to provide a better understanding of the involved aerodynamic phenomena.

关键词： Blade Element Momentum Theory computational fluid dynamics simulation National Renewable Energy Laboratory Freestream Velocity Aerodynamic Performance Vortices Helicopter Rotor Blade Vortex Interaction Reynolds Averaged Navier Stokes Blade Pitch Control

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Stagnation-Point Aeroheating Correlations for Mars Entry

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JOURNAL OF SPACECRAFT AND ROCKETS 2020年第2期57卷 319-327页

作者： West, Thomas K. Brandis, A. M. NASA Langley Res Ctr Vehicle Anal Branch Syst Anal & Concepts Directorate Hampton VA 23681 USA Analyt Mech Associates Inc Aerothermodynam Branch NASA Ames Res Ctr Moffett Field CA 94035 USA

This work details the development of new stagnation-point aeroheating engineering correlations for Mars entry vehicles. Convective and radiative heating relations were formulated over a wide range of entry conditions. These relations were based on computational fluid dynamics simulations informed by recent experimental testing and modeling enhancements. For convective heating, a relation similar to those proposed in previous works was developed that is accurate to within +/- 25% across the domain of relevant Mars entry conditions. For radiative heating, two different functional forms were developed: exponential and polynomial relations. Each of these relations, which represents two different levels of complexity for implementation, were able to predict the radiative heating within about +/- 25%. The correlations were tested by applying them to the Mars Pathfinder entry trajectory to demonstrate their applicability. These new correlations provide significant improvement over existing relations in terms of the accuracy, the domain of applicability, and the captured physics, including CO2 infrared radiation and thermochemical nonequilibrium.

关键词： Stagnation Point Radiative Heating computational fluid dynamics simulation Mars Pathfinder Vacuum Ultraviolet Radiation Freestream Conditions Heat Transfer Chemical Equilibrium Aerodynamic Heating Prandtl Number

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Mass Transport Control by Surface Graphene Oxide for Selective CO Production from Electrochemical CO2 Reduction

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ACS CATALYSIS 2020年第5期10卷 3222-+页

作者： Dang Le Tri Nguyen Lee, Chan Woo Na, Jonggeol Kim, Min-Cheol Nguyen Dien Kha Tu Lee, Si Young Sa, Young Jin Won, Da Hye Oh, Hyung-Suk Kim, Heesuk Min, Byoung Koun Han, Sang Soo Lee, Ung Hwang, Yun Jeong KIST Clean Energy Res Ctr Seoul 02792 South Korea Korea Univ Green Sch Seoul 02841 South Korea Korea Univ Sci & Technol UST KIST Sch Div Energy & Environm Technol Seoul 02792 South Korea Yonsei Univ Yonsei KIST Convergence Res Inst Dept Chem & Biomol Engn Seoul 03722 South Korea Duy Tan Univ Inst Res & Dev Da Nang 550000 Vietnam Kookmin Univ Dept Chem Seoul 02707 South Korea KIST Computat Sci Res Ctr Seoul 02792 South Korea KIST Photoelect Hybrids Res Ctr Seoul 02792 South Korea KIST Natl Res Agenda Div Seoul 02792 South Korea

Electrochemical CO2 reduction is always accompanied by a competitive hydrogen evolution reaction as water is used as a hydrogen source. In addition to intrinsic activity control, geometrical factors of electrocatalysts such as their porous structure have been demonstrated to affect the reaction selectivity, but understanding its origin is still important. Herein, we demonstrate that reduced graphene oxide layers can effectively control the Faradaic efficiency for CO production of porous zinc nanoparticle electrocatalysts. Simply tuning for CO production from 66 to 94% even in the bicarbonate electrolyte the coverage of graphene oxide dramatically varies Faradaic efficiency at the same biased potential, in which the hydrogen evolution rate was notably suppressed without sacrificing CO2 reduction to CO production rate unlike many Zn-based electrocatalysts. The graphene oxide layers are revealed to play roles in providing geometric barriers for the mass transport channels of reactants rather than changing the chemical states of the Zn-based electrocatalysts according to in situ X-ray absorption spectroscopic analysis and electrochemical reaction kinetic studies. In addition, computational fluid dynamics simulation studies estimate the Faradaic efficiency dependence on the surface coverage and suggest that the selective suppression of H-2 evolution is associated with the larger increment in local pH compared to that in local pCO(2) at the porous electrocatalyst surfaces. Decoupling between these reactant concentrations is originated from the higher consumption rate and lower bulk concentration of proton compared to those of CO2, and the surface coating with graphene oxide can be an effective way to control mass transport channel.

关键词： electrochemical CO2 reduction suppression of H-2 evolution Zn-based catalyst reduced graphene oxide computational fluid dynamics simulation

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Numerical simulation on Optimization of Pintle Base Shape in Planar Expansion-Deflection Nozzles

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JOURNAL OF SPACECRAFT AND ROCKETS 2020年第3期57卷 539-548页

作者： Paul, John P. Nair, Prasanth P. Suryan, Abhilash Martin, Joe Paul M. Dong Kim, Heuy Coll Engn Trivandrum Dept Mech Engn Trivandrum 695016 Kerala India Infosys Ltd Infosys Engn Serv Mysore 570027 Karnataka India Andong Natl Univ Dept Mech Engn Andong 760749 South Korea

Altitude compensating nozzles provide optimum performance over a wide range of altitudes. The planar expansion-deflection nozzle is one such nozzle. It has a rectangular cross-section, and altitude compensation is achieved by incorporating a pintle beyond the throat of a conventional convergent-divergent nozzle. The objective of the present Paper is to investigate the variations in flow caused as a result of a varying pintle base shape in a planar expansion-deflection nozzle. The computational fluid dynamics approach is used for conducting the analysis. Nozzle contour and pintle geometry up to the throat is kept unchanged, and simulations are conducted by altering the geometry of the pintle base profile. For each expansion-deflection nozzle configuration, the flow pattern, base pressure, and coefficient of thrust generated by nozzle are studied over a range of nozzle pressure ratios. The results of the numerical study reveal that the curved pintle with highest base curvature showed better overall performance in terms of contribution of base pressure to thrust output, whereas the pintle with an inclined base indicated the better overall coefficient of thrust when compared to pintles at higher nozzle pressure ratios due to higher contribution from momentum thrust.

关键词： computational fluid dynamics simulation Altitude Compensating Nozzle Momentum Thrust Turbulent Flow Flow Separation Reynolds Averaged Navier Stokes Flow Characteristics Turbulence Kinetic Energy Rocket Design Aerospike Nozzle

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Study on filtration performance of elliptical fiber with different arrangements

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JOURNAL OF ENGINEERED FIBERS AND FABRICS 2020年第15期15卷

作者： Zhou, JiaWei Zhang, Liang Zhang, Bo Gong, Wei Southwest Petr Univ Chengdu 610500 Sichuan Peoples R China PetroChina Southwest Oil & Gasfield Co Chongqing Peoples R China

The fibrous media composed of elliptical fibers is widely used owing to the high filtration efficiency. However, there are few studies on the arrangement of non-circular fibers, although the single non-circular fiber has been clearly investigated. In this article, two-dimensional numerical geometries of fibrous media with different elliptical fiber arrangements, namely, random distribution structure, dense-sparse structure, and bimodal structure, are developed for studying filtration performance. The results show that the large aspect ratio and solid volume fraction represent low particle penetration. When the particle diameter (D-p) is small, the quality factor of bimodal structure is higher than the dense-sparse structure, especially atD(p) = 50 nm. For the largeD(p), the opposite is true. Meanwhile, reducing fiber diameter (D-f) is more significant than increasing solid volume fraction in terms of improving penetration. As for dense-sparse structure, replacing the elliptical fibers in sparse layers with circular fibers can comprehensively improve the quality factor of fibrous media. However, if the replacement between elliptical fiber and circular fiber occurs in dense layer, it will result in high quality factor atD(p) <= 500 nm, while low quality factor atD(p) > 500 nm.

关键词： computational fluid dynamics simulation fibrous media elliptical fiber different arrangements penetration

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Aeroelastic Reduced Order Model: Kriging-Corrected Potential Flow

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JOURNAL OF AIRCRAFT 2020年第3期57卷 501-516页

作者： Horwitz, Roy A. D. Malan, Arnaud G. Braithwaite, James Univ Cape Town Dept Mech Engn Elect & Mech Engn BldgLib Rd ZA-7700 Cape Town South Africa

A novel aeroelastic reduced order model is developed for two-dimensional gust interaction modeling in transonic flows. Such conditions exhibit a key nonlinearity: sonic shock motion. The proposed approach comprises an aerodynamics reduced order model coupled to a structural model. The aerodynamics model consists of corrected integrated force coefficients computed by an unsteady potential flow method (incompressible vortex panels). The corrections are obtained from kriging surrogates trained using inviscid compressible computational fluid dynamics data. Two gust lengths (namely, long and short) are simulated for this purpose and serve as the upper and lower bounds of the model. The developed aeroelastic reduced order model is evaluated via modeling untried gust cases, the lengths of which fall between the training cases. Applied to the FFAST Crank and NACA0012 airfoils, the approach accurately reproduces aeroelastic response-with deviations never exceeding 8.0 and 10.5%, respectively. In terms of computational cost, the trained models were more than an order of magnitude faster than the computational fluid dynamics simulations.

关键词： Flow Conditions computational fluid dynamics simulation Aerodynamic Force Coefficients Aeroelastic Analysis Structural Modeling Vortex Strength Reynolds Averaged Navier Stokes Lift Coefficient Arbitrary Lagrangian Eulerian Kelvin's Circulation Theorem

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Pedestrian wind comfort near a super-tall building with various configurations in an urban-like setting

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建筑模拟（英文版） 2020年第6期13卷 1385-1408页

作者： Xinyue Zhang Asiri Umenga Weerasuriya Xuelin Zhang Kam Tim Tse Bin Lu Cruz Yutong Li Chun-Ho Liu Department of Architectural and Civil Engineering City University of Hong Kong Tat Chee Ave Kowloon Tong Hong Kong China Department of Civil and Environmental Engineering The Hong Kong University of Science and Technology Clear Water Bay Kowloon Hong Kong China Department of Mechanical Engineering The University of Hong Kong Pokfulam Hong Kong China School of Atmospheric Sciences Sun Yat-sen University Guangzhou China

Pedestrian wind comfort near a 400 m super-tall building in high and low ambient wind speeds, referred to as Windy and Calm climates, is evaluated by conducting computational fluid dynamics (CFD) simulations. The super-tall building has 15 different configurations and is located at the center of 50 m medium-rise buildings in an urban-like setting. Pedestrian level mean wind speeds near the super-tall building is obtained from three-dimensional (3D), steady-state, Reynolds-Averaged Navier-Stokes (RANS)-based simulations for five incident wind directions (θ = 0°, 22.5°, 45°, 90°, 180°) that are subsequently compared with two wind comfort criteria specified for Calm and Windy climates. Results show a 1.53 times increase in maximum mean wind speed in the urban area after the construction of a square-shaped super-tall building. The escalated mean wind speeds result in a 23％–15％ and 36％–29％ decrease in the area with 'acceptable wind comfort' in Calm and Windy climates, respectively. The area with pedestrian wind comfort varies significantly with building configuration and incident wind direction, for example, the configurations with sharp corners, large plan aspect ratios and, frontal areas and the orientation consistently show a strong dependency on incident wind direction except for the one with rounded plan shapes. Minor aerodynamic modifications such as corner modifications and aerodynamically-shaped configurations such as tapered and setback buildings show promise in improving pedestrian wind comfort in Windy climate.

关键词： pedestrian wind comfort super-tall building building configuration urban wind environment computational fluid dynamics simulation

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