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Conduction-convection coupled heat transfer around a hollow cylinder under different buoyancy forces

Chinese Journal of Aeronautics 2024年第4期37卷 216-228页

作者： Wanyu ZHANG Jingyi WU Guang YANG Institute of Refrigeration and Cryogenics Shanghai Jiao Tong UniversityShanghai 200240China

In order to clarify the effect of a buoyancy force on conduction–convection coupled heat transfer in a hollow cylinder, the flow and thermal characteristics were analyzed using an RNG k-ε turbulence model. The Reynolds number was fixed at 1.014 × 10^(6), and the Rayleigh number varied from 1.122 × 10^(10)to 1.088 × 10^(11). Results have shown that, when considering the effect of an opposed buoyancy force, increasing the Rayleigh number has a positive impact on the rate of change and uniformity of the cylinder temperature. The temperature distributions along the axial and circumferential directions are similar for different Rayleigh numbers, but extreme values differ.Along the axial direction, the maximum temperature is obtained at the interface between the variable-diameter part and the constant-diameter part. The maximum dimensionless temperature value decreases to 0.12 when the Rayleigh number increases to 1.088 × 10^(11). Along the circumferential direction, the temperature distribution is affected by the buoyancy force, which results in the temperature of the upper part being higher than that of the lower part. After nondimensionalization of the temperature and time, a correlation was proposed to illustrate the transient heat transfer process quantitatively. The standard deviation of the maximum relative temperature, representing the temperature uniformity, was also calculated. It was found that the difference in the direction of the buoyancy force made a huge difference. Compared with the opposed buoyancy force, the maximum dimensionless temperature is almost two times higher with an assisted buoyancy force. Similarly, the heat transfer coefficient with an assisted buoyancy force is half of that with an opposed buoyancy force. Overall, an assisted buoyancy force plays a negative role in terms of thermal characteristics. The flow field around the hollow cylinder was also illustrated to reveal the mechanism of the buoyancy force on magnitude and direction aspects.

关键词： buoyancy Conduction-convection heat transfer Transient analysis Hollow cylinder Non-dimensionalization

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Morphometry and Mineral Content in the Seeds and Soil of Two Species of Argemone L.(Papaveraceae)in the Central Part of the Chihuahuan Desert

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Phyton-International Journal of Experimental Botany 2024年第2期93卷 371-386页

作者： Perla Patricia Ochoa-García Jaime Sánchez-Salas Ricardo Trejo-Calzada Jesús JosafathQuezada-Rivera Fabián García-González Unidad Regional Universitaria de ZonasÁridas BermejilloUniversidad Autónoma ChapingoDurango35230México Facultad de Ciencias Biológicas Universidad Juárez del Estado de DurangoGómez PalacioDurango35010México

The genus Argemone L.(Papaveraceae)is found widely distributed in Mexico’s Chihuahuan Desert(CD).Some species of this genus are of phytochemical or ethnobotanical interest.They are inedible plants considered as scrubs.To date they have not been broadly studied;thus,their ecology is,to our knowledge,unknown.The present work was centered around carrying out a morphometric analysis and the determination of minerals in the soil and seeds of the wild populations of Argemone at sites belonging to two ecoregions of the CD in Mexico.In April 2021 and April 2022,seeds of Argemone spp.,and soil samples were collected at 10 sites of the CD.The seeds were selected under a randomized design,and weight,length,diameter,thickness,buoyancy,and mineral content were determined.The soil samples were obtained under the Mexican regulation NOM-021-RECNAT-2000,and determinations of mineral content,electrical conductivity,apparent density,and soluble anions were performed.The information obtained was grouped by variable,species,and place of precedence.The statistical tests consisted of an ANOVA,Tukey means tests considering p≤0.05,and a Principal Components Analysis.Argemone pleiacantha exhibited differences in terms of weight(F=54.79,p=0.001),length(F=90.83,p=0.001),thickness(F=104.89,p=0.001),and diameter(F=155.82,p=0.001),and the differences in Argemone mexicana were in weight(F=46.71,p=0.001),thickness(F=187.49,p=0.001),length(F=191.56,p=0.001),and diameter(F=215.83,p=0.001).The evaluated seeds reached their maximal imbibition velocity at 24 h of evaluation.The content of the micro-and macro-nutrients analyzed in the seeds and soil suggest a tight relation with the morphometric characteristics of the seeds.

关键词： Micronutrients agricultural area semiarid zone ecoregion buoyancy

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Transfer of the zp3a gene results in changes in egg adhesiveness and buoyancy in transgenic zebrafish

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Zoological Research 2023年第2期44卷 259-268页

作者： Yu-Qing Cao Yong-Xin Wang Yan Zhao Jia Zhang Xian He Ping Xie Jun Chen Yu-Hua Sun Institute of Hydrobiology Chinese Academy of SciencesWuhanHubei 430072China Innovation Academy for Seed Design Chinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China Donghu Experimental Station of Lake Ecosystems State Key Laboratory of Freshwater Ecology and BiotechnologyInstitute of HydrobiologyChinese Academy of SciencesWuhanHubei 430072China

Reproductive strategies and spawning habits play key roles in the evolution of endemic East Asian cyprinids.However,the molecular mechanisms underlying the regulation of spawning habits are not well understood.We recently identified zona pellucida(Zp) as the top differentially expressed protein between East Asian cyprinids that produce adhesive and semi-buoyant eggs,suggesting that Zp protein may play important roles in the regulation of egg type.In this work,we generated transgenic zebrafish in which oocyte-specific expression of zp genes from rare minnow(Gobiocypris rarus),an East Asian cyprinid laying adhesive eggs,was driven by a zebrafish zp3.2 gene promoter.We found that the transgenic eggs obtained partial adhesiveness and exhibited alteration in hydration and buoyancy.Abnormal metabolism of vitellogenin(VTG) may contribute to enhanced hydration and/or buoyancy.Our work shows that expression of the exogenous zp3a gene from an adhesiveegg producing fish is sufficient to induce changes in both egg adhesiveness and buoyancy in zebrafish,emphasizing the important role of zp genes in the regulation of spawning habits.Our results thus provide new insights into how endemic East Asian cyprinids may have adapted to the Yangtze river-lake system via changes in spawning habits.

关键词： Zona pellucida protein Adhesive buoyancy Hydration Egg envelope

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Cracking and buoyancy effect on hydrocarbon endothermic and heat transfer characteristics in rectangular mini-channel

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Chinese Journal of Chemical Engineering 2023年第4期56卷 242-254页

作者： Chengang Yang Huaizhi Han Quan Zhu Xiangyuan Li School of Chemical Engineering Sichuan UniversityChengdu 610065China Engineering Research Center of Combustion and Cooling for Aerospace Power Ministry of EducationSichuan UniversityChengdu 610065China

Although buoyancy and cracking reactions are strongly coupled in the active cooling process, most of the previous studies consider only one of these factors, and their coupling relationship has not been considerably examined. In this work, this coupling relationship was numerically investigated with complete consideration of different cases of heating, and in the view of energy transport and conversion. By comparing with the no-gravity case(NGC), the results indicate that buoyancy has a significant effect on the bottom-heated case(BHC) and side-heated case(SHC), but has little influence on the top-heated case(THC) owing to the different magnitudes of secondary flow. The heat transfer of the BHC and SHC was significantly enhanced by the secondary flow, but their energy conversion was simultaneously impaired.The conversion of the BHC and SHC was approximately half that of the THC and NGC. For all cases, by analyzing the energy transport ways, the cross section can be classified into three regions in the heating direction. Laminar conduction dominates in region Ⅰ, but gradually fails in region Ⅱ, where its role is replaced by other energy transport ways. In region Ⅲ, convection dominates the energy transport for BHC and SHC, whereas turbulence dominates for THC and NGC.

关键词： Heat transfer Computational fluid dynamics(CFD) buoyancy Hydrocarbons

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buoyancy leads to high productivity of the Changjiang diluted water:a note

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Acta Oceanologica Sinica 2008年第6期27卷 133-140页

作者： CHEN Chen-Tung Arthur Institute of Marine Geology and Chemistry National Sun Yat-sen University State Key Laboratory of Marine Environmental Science Xiamen University

Being the mightiest river emptying into the East China Sea （ECS） and the Pacific Ocean, compounded with the large increase of nitrogen and phosphorus input due to anthropogenic activities, the Changjiang River （Yangtze River） has become a dominating source of these nutrients to the estuary. The high nutrient concentrations notwithstanding, however, outside of the estuary the high biological productivity of the Changjiang diluted water （CDW） are most probably fueled mainly by nutrient-rich subsurface waters originating from the upwelled Kuroshio waters. This is because while the buoyancy of the CDW spreads it out on the ECS continen- tal shelf, the CDW entrains subsurface waters along with the nutrients. Nutrients thus supplied are several times more than those supplied by the Changjiang River.

关键词： Changjiang River Changjiang diluted water nutrients Three Gorges Dam productivity buoyancy

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How did Archimedes discover the law of buoyancy by experiment？

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Frontiers of Mechanical Engineering 2016年第1期11卷 26-32页

作者： Hidetaka KUROKI Okazaki Aichi-ken 444-0076 Japan

After Archimedes and Vitruvius era, for more than 2000 years, it has been believed that the displaced water measurement of golden crown is impossible, and at his Eureka moment, Archimedes discovered the law of buoyancy （Proposition 7 of his principles） and proved the theft of a goldsmith by weighing the golden crown in water. A previous study showed that a small amount of displaced water was able to be measured with enough accuracy by the introduced method. Archimedes measured the weight of displaced water. He did not find the law of buoyancy but rather specific gravity of things at the moment. After which, Archimedes continued to measure the specific gravity of various solids and fluids. Through these measurements, he reached the discovery of the law of buoyancy directly by experiment. In this paper, the process to the discovery of Archimedes＇ principle （Proposition 5） is presented.

关键词： Archimedes＇ principle buoyancy specific gravity Eureka Vitruvius displaced water balance,floating body

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Numerically quantifying the relative importance of topography and buoyancy in driving groundwater flow

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Science China Earth Sciences 2010年第1期53卷 64-71页

作者： YANG JianWen 1,2,FENG ZuoHai 1,LUO XianRong 1 & CHEN YuanRong 1 1 Faculty of Earth Sciences,Guilin University of Technology,Guilin 541004,China 2 Department of Earth and Environmental Sciences,University of Windsor,Windsor,Ontario,N9B 3P4,Canada Faculty of Earth Sciences Guilin University of Technology Guilin China Department of Earth and Environmental Sciences University of Windsor Windsor Canada

Both topography and buoyancy can drive groundwater flow;however,the interactions between them are still poorly understood.In this paper,the authors conduct numerical simulations of variable-density fluid flow and heat transport to quantify their relative importance.The finite element modeling experiments on a 2-D conceptual model reveal that the pattern of groundwater flow depends largely upon the relative magnitude of the flow rate due to topography alone and the flow rate due to buoyancy alone.When fluid velocity due to topography is greater than that due to buoyancy at large water table gradients,topography-driven 'forced convection' overwhelms buoyancy-driven 'free convection'.When flow velocity due to buoyancy is greater than that due to topography at small water table gradients,mixed free and forced convection takes place.In this case,free convection becomes dominant,but topography-driven flow still plays an important role since it pushes the free convection cells to migrate laterally in the downhill direction.Consequently,hydrothermal fluid flow remains changing periodically with time and no steady state can be reached.The presence of a low-permeability layer near the surface helps eliminate the topography effect on the underlying free convection.

关键词： hydrothermal flow free convection forced convection topography buoyancy finite element modeling

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Analysis of buoyancy Module Auxiliary Installation Technology Based on Numerical Simulation

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Journal of Ocean University of China 2018年第2期17卷 267-280页

作者： XU Songsen JIAO Chunshuo NING Meng DONG Sheng Drilling Technology Research Institute of Shengli Petroleum Engineering Corporation Limited SINOPEC College of Engineering Ocean University of China

To reduce the requirement for lifting capacity and decrease the hoist cable force during the descending and laying process of a subsea production system(SPS), a buoyancy module auxiliary installation technology was proposed by loading buoyancy modules on the SPS to reduce the lifting weight. Two models are established, namely, the SPS lowering-down model and the buoyancy module floating-up model. The main study results are the following: 1) When the buoyancy module enters the water under wave condition, the amplitude of tension fluctuation is twice that when SPS enters water; 2) Under current condition, the displacement of SPS becomes three times larger because of the existence of the buoyancy module; 3) After being released, the velocity of the buoyancy module increases to a large speed rapidly and then reaches a balancing speed gradually. The buoyancy module floats up at a balancing speed and rushes out from the water at a pop-up distance; 4) In deep water, the floating-up velocity of the buoyancy module is related to its mass density and shape, and it is not related to water depth; 5) A drag parachute can reduce floating-up velocity and pop-up distance effectively. Good agreement was found between the simulation and experiment results.

关键词： buoyancy module subsea production system rope tension disturbance floating-up velocity drag parachute pop-up distance

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Study on buoyancy convection phenomenon in the crystal growth process

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Science China(Technological Sciences) 2009年第8期52卷 2367-2372页

作者： DUAN Li KANG Qi National Microgravity Laboratory Institute of MechanicsChinese Academy of SciencesBeijing 100190China

Real-time phase shift Mach-Zehnder interference technique, imaging technique, and computer image processing technique were combined to perform a real-time diagnosis of NaClO3 crystal, which de- scribed both the dissolution process and the crystallization process of the NaClO3 crystal in real-time condition. The dissolution fringes and the growth fringes in the process were obtained. Moreover, a distribution of concentration field in this process was obtained by inversion calculation. Finally, the buoyancy convection phenomenon caused by gravity in the crystal growth process was analyzed. The results showed that this convection phenomenon directly influences the growth rate of each crystal face in the crystal.

关键词： crystal growth interferometry buoyancy convection

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Stability of flow between rotating cylinders with axial buoyancy effect

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Science China(Physics,Mechanics & Astronomy) 2006年第5期49卷 564-575页

作者： CHEN Jianguo CHEN Haixin ZHANG Guanghua FU Song Department of Engineering Mechanics School of AerospaceTsinghua UniversityBeijing 100084China Department of Engineering MechanicsSchool of AerospaceTsinghua UniversityBeijing 100084China Department of Engineering MechanicsSchool of AerospaceTsinghua UniversityBeijing 100084China Department of Engineering MechanicsSchool of AerospaceTsinghua UniversityBeijing 100084China

The linear stability of a fluid confined between two coaxial cylinders rotating independently with axial buoyancy induced flow is examined. buoyancy is included through the Boussinesq approximation. The numerical investigation is restricted to radius ratio 0.5 at Prandtl number 0.709 with co-rotation situation. The outer rotating cylinder’s Couette flow Reynolds number is restricted to 200. Zeroth-order discontinuities are found in the critical surface, which are explained as the result of the competition between the centrifugal and axial buoyancy induced shear instability mechanisms. Due to the competition, the neutral stability curves develop islands of instability, which considerably lower the instability threshold. Specific and robust numerical methods to handle these geometrical complexities are developed.

关键词： island of instability cylinder rotation buoyancy flow

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