检索结果-内蒙古大学图书馆

Intermediate viscosity in a gravity-driven flow and its application to simple viscometry

JOURNAL OF RHEOLOGY 2025年第2期69卷 131-138页

作者： Mizunuma, Hiroshi Tokyo Metropolitan Univ Dept Mech Engn 1-1 Minamiohsawa Hachioji Tokyo 1920397 Japan

In a capillary tube flow, if the wall shear stress tau w and apparent shear rate 4V/R are given, the viscosity reduces to the viscosity tau(w)/(4V/R) at a dimensionless intermediate radius r(a)* (equivalent to r(a)/R) of approximately 0.8, where the shear rate is ra* x 4V/R. This known result is extended to the quasi-steady gravity-driven flow in a capillary tube, where the fluid head decreases from H-max to H over a period of T seconds. Using a Carreau and power-law model, the intermediate viscosity for a gravity-driven flow is derived for the logarithmic middle fluid head between H-max and H. This intermediate viscosity and its shear rate can be obtained from a single measurement of T using a flow setup like an Ubbelohde viscometer. The experimental results validate the proposed method and show its potential for an easy and inexpensive viscometry oriented toward practical applications, like the viscosity measurement of a liquid diet for dysphagia.

关键词： capillary viscometer intermediate viscosity gravity-driven flow shear thinning fluid dysphagia liquid care food Ubbelohde viscometer

来源：评论

学校读者我要写书评

暂无评论

Computational-Analysis of the Non-Isothermal Dynamics of the gravity-driven flow of Viscoelastic-Fluid-Based Nanofluids Down an Inclined Plane

引用

Fluid Dynamics & Materials Processing 2023年第3期19卷 767-781页

作者： Idrees Khan Tiri Chinyoka Andrew Gill Centre for Research in Computational&Applied Mechanics University of Cape TownRondebosch7701South Africa Department of Mathematics and Applied Mathematics University of Cape TownRondebosch7701South Africa Centre for High Performance and Computing Council for Scientific and Industrial ResearchRosebankCape Town7700South Africa

The paper explores the gravity-driven flow of the thin film of a viscoelastic-fluid-based nanofluids(VFBN)along an inclined plane under non-isothermal conditions and subjected to convective cooling at the *** Newton’s law of cooling is used to model the convective heat-exchange with the ambient at the *** Giesekus viscoelastic constitutive model,with appropriate modifications to account for non-isothermal effects,is employed to describe the polymeric *** unsteady and coupled non-linear partial differential equations(PDEs)describing the model problem are obtained and solved via efficient semi-implicit numerical schemes based on finite difference methods(FDM)implemented in *** response of the VFBN velocity,temperature,thermal-conductivity and polymeric-stresses to variations in the volume-fraction of embedded nanoparticles is *** is shown that these quantities all increase as the nanoparticle volume-fraction becomes higher.

关键词： Semi-implicit numerical scheme finite difference methods viscoelastic-fluid-based nanofluid(VFBN) nonisothermal viscoelastic flow giesekus constitutive model nanofluid thermal-conductivity gravity-driven flow

来源：评论

学校读者我要写书评

暂无评论

Dynamic response of gravity-driven flow in multi-section absorption heat pump

引用

APPLIED THERMAL ENGINEERING 2022年 200卷 117622-117622页

作者： Zhu, Chaoyi Xie, Xiaoyun Jiang, Yi Tsinghua Univ Bldg Energy Res Ctr Dept Bldg Sci Beijing 100084 Peoples R China Tsinghua Univ Inst Nucl & New Energy Technol Beijing 100084 Peoples R China

The multi-section absorption heat pump (AHP) is applied in the novel district heating (DH) system of China. This new type of AHP exhibits improved performance in DH systems, but involves a more complicated structural design and the risk of internal flow instability problems such as reversed pressure difference and liquid accu-mulation. The flow circulations of the solution and refrigerant consist of several gravity-driven flow processes that are rarely observed in conventional AHPs, and these processes have not been addressed in previous studies. The present work studies the dynamic response of gravity-driven flow inside a multi-section AHP in a DH system. A dynamic model capable of calculating the liquid level, flow rate, and pressure change of various gravity-driven flow processes is developed and validated. The steady-state conditions calculated by the dynamic model are compared with a validated model in the literature. The gap between the temperature and pressure calculations is less than 0.3 K and 0.05 kPa, respectively. The dynamic simulation results are compared with the start-up process test results of a multi-section AHP. The pressure values and trend change fit the test results well. The standard deviation (SD) and root-mean-square error (RMSE) of the pressure calculation errors are less than 5% and 5.5%, respectively. The model is used to study typical transient processes of multi-section AHPs in a DH system. In the start-up process, the pressure of the generator is 1-2 kPa lower than that of the absorber after the solution circulation begins. This reversed pressure difference leads to solution accumulation at the bottom of the generator. The solution flow rate into the absorber is 20% lower than the designed value. After the heat source is input into the generator, the reversed pressure difference disappears. Solution accumulation expedites the flow of the solution into the absorber. The flow rate is 75% higher than that of the designed value, leading to

关键词： Absorption heat pump gravity-driven flow Dynamic modeling District heating

来源：评论

学校读者我要写书评

暂无评论

Enhanced flow Boiling of Ethanol in Open Microchannels With Tapered Manifolds in a gravity-driven flow

引用

JOURNAL OF HEAT TRANSFER-TRANSACTIONS OF THE ASME 2016年第3期138卷 031503-031503页

作者： Buchling, Philipp Kandlikar, Satish Rochester Inst Technol Dept Mech Engn Lomb Mem Dr Rochester NY 14623 USA

There is a clear need for cooling high heat flux generating electronic devices using a dielectric fluid without using a pump. This paper explores the feasibility of employing ethanol as a dielectric fluid in a horizontal, open microchannel heat sink configuration with a tapered gap manifold to yield very low pressure head requirements. The paper presents experimental results for such a system utilizing ethanol as a working fluid under gravity-driven flow. A heat flux of 217 W/cm(2) was dissipated with a pressure drop of only 9 kPa. The paper further presents parametric trends regarding flow rate and pressure drop characteristics that provide basic insight into designing high heat flux systems under a given gravity head requirement. Based on the results, interrelationships and design guidelines are developed for the taper, ethanol flow rate and imposed heat flux on heat transfer coefficient and gravity head requirement for electronics cooling. Reducing flow instability, reducing pressure drop, and enhancing heat transfer performance for a dielectric fluid will enable the development of pumpless cooling solutions in a variety of electronics cooling applications.

关键词： open microchannels OMM tapered manifolds flow boiling electronics cooling gravity-driven flow low pressure drop ethanol

来源：评论

学校读者我要写书评

暂无评论

gravity-driven thermally stratified nanofluid flow past a permeable stretching surface

引用

PRAMANA-JOURNAL OF PHYSICS 2025年第1期99卷 1-11页

作者： Konai, Saheb Mukhopadhyay, Swati Univ Burdwan Dept Math Burdwan 713 104 India

This study offers an analysis of the gravity-driven thermally stratified laminar nanoliquid flow past a permeable stretching surface with vanishing flux of nanoparticles. Two-phase fluid model is used for the nanofluids. By the application of similarity transformations, the partial differential equations (PDEs) that govern the problem are converted to ordinary differential equations (ODEs) which are extremely nonlinear. By using the shooting technique and Runge-Kutta (R-K) method, those equations are numerically solved. Shear stress at the surface and rate of surface mass transfer decrease but rate of heat transport at the surface rises for the enhancement of mass transpiration parameter. Temperature and concentration of the nanofluid are found to fall, but the liquid's velocity rises with the rising buoyancy parameter. Concentration of the nanofluid increases but velocity of the liquid and temperature diminish when the thermal stratification parameter increases.

关键词： Nanofluid two-phase fluid model gravity-driven flow thermal stratification zero mass flux 47.15.Cb 44.20.+b 66.10.cg

来源：评论

学校读者我要写书评

暂无评论

Granular Segregation in gravity-driven, Dense, Steady, Fluid-Particle flows over Erodible Beds and Rigid, Bumpy Bases

引用

WATER 2023年第14期15卷 2629页

作者： Jenkins, James T. Larcher, Michele Cornell Univ Sch Civil & Environm Engn Ithaca NY 14850 USA Free Univ Bozen Bolzano Fac Engn I-39100 Bolzano Italy

Kinetic theory is used to propose and solve boundary value problems for fully developed, steady, dense gravity-driven flows of mixtures composed of identical inelastic spheres and water over both inclined erodible beds and rigid, bumpy bases confined by vertical sidewalls. We solve the boundary value problems assuming values of the mass density and of the size of the spheres typical of natural materials and show the numerical solutions for the profiles of the mean velocities of the particles and fluid, the intensity of the particle velocity fluctuations, and the granular concentration. In addition, we indicate how the features of the grain velocity fluctuations profile would influence segregation in three situations when the particle phase consists of two sizes of spheres: (1) the spheres are of the same material, and only gradients of temperature influence their segregation;(2) the mass densities of the material of the spheres are such that only gravity influences segregation;and (3) the mass densities are such that the coefficients of the temperature gradients and gravity segregation mechanisms are equal. For spheres of the same material, over a rigid bumpy base, the concentration of larger spheres increases from zero at the bed to the maximum value at the top of the flow;while over an erodible bed, this concentration has its maximum value at both the bed and the top of the flow.

关键词： granular flow kinetic theory granular segregation gravity-driven flow fluid-particle flow binary mixture granular temperature gravity-driven segregation

来源：评论

学校读者我要写书评

暂无评论

An analytical comprehensive solution for the superficial waves appearing in gravity-driven flows of liquid films

引用

ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK 2020年第4期71卷 122-122页

作者： Chimetta, Bruno Pelisson Franklin, Erick UNICAMP Univ Campinas Sch Mech Engn Rua Mendeleyev 200 BR-13083860 Campinas Brazil

This paper is devoted to analytical solutions for the base flow and temporal stability of a liquid film driven by gravity over an inclined plane when the fluid rheology is given by the Carreau-Yasuda model, a general description that applies to different types of fluids. In order to obtain the base state and critical conditions for the onset of instabilities, two sets of asymptotic expansions are proposed, from which it is possible to find four new equations describing the reference flow and the phase speed and growth rate of instabilities. These results lead to an equation for the critical Reynolds number, which dictates the conditions for the onset of the instabilities of a falling film. Different from previous works, this paper presents asymptotic solutions for the growth rate, wavelength and celerity of instabilities obtained without supposinga priorithe exact fluid rheology, being, therefore, valid for different kinds of fluids. Our findings represent a significant step toward understanding the stability of gravitational flows of non-Newtonian fluids.

关键词： gravity-driven flow Generalized Newtonian fluid Carreau-Yasuda model Temporal stability Asymptotic method

来源：评论

学校读者我要写书评

暂无评论

Heat source/sink impact on wave oscillations of thermal and concentration boundary layer along inclined plate under lower gravitational region

引用

CASE STUDIES IN THERMAL ENGINEERING 2024年 53卷

作者： Al-Shammari, Hammad Ullah, Zia Ilyas, Asifa Aldhabani, Musaad S. Alkathiri, Eman T. El-Sayed, Mohamed E. Murshed, Mohammad N. Hassan, Ahmed M. Jouf Univ Dept Mech Engn Sakaka 72388 Saudi Arabia Univ Lahore Dept Math & Stat Sargodha Campus 40100 Sargodha Pakistan Univ Sargodha Fac Sci Dept Math Sargodha 40100 Pakistan Univ Tabuk Fac Sci Dept Math POB 741 Tabuk 71491 Saudi Arabia Najran Univ Fac Sci & Arts Sharurah Dept Math Najran Saudi Arabia King Khalid Univ Fac Sci & Arts Phys Dept Muhayl Asser Saudi Arabia Future Univ Egypt Fac Engn & Technol Cairo 11835 Egypt

The force of attraction between two masses increases as gravity increases. gravity is very important mechanism for mass transfer characteristics across the inclined shape. The significant purpose of current study is to examine amplitude in mass transfer under reduced gravity-driven flow. The impact of heat source/sink on periodic mixed convective gravity-driven flow across the inclined plate has been evaluated. The oscillatory characteristics of heat rate and mass transmission are explored at three inclined angles pi /6, pi /4 and pi /3. The gravity is assumed under maximum temperature difference. The governing dimensional model is transformed into non dimensional equations with appropriate scaling variables. The non-dimensional equations are again reduced in non-oscillatory, real and imaginary parts. For smooth coding, the primitive formulation is used with finite difference method to change non-dimensional forms in algebraic system. The algebraic equations are solved with Gaussian elimination scheme to display velocity field, temperature distribution and rate of concentration numerically. The impact of heat source/ sink +/-delta, reduced gravity Rg, buoyancy variable lambda T, modified buoyancy factor lambda C, Prandtl factor Pr, reduced gravitation factor Rg, and Schmidt variable Sc on the oscillating behavior of shear stress, rate of fluctuating heat transfer, and rate of fluctuating mass transfer is secured. It is found that the amplitude of fluid velocity and temperature increases for each parameter under heat source + delta= 0.4. It can be seen that concentration distribution increases as reduced gravity Rg increases under heat sink delta= 0.3. It can be seen that amplitude of shearing stress and heat transfer increases as heat source +delta increases. It is obtained that oscillation in mass transfer increases as heat source/sink +/-delta increases under reduced gravitation Rg = 1.2.

关键词： Mass transfer Oscillatory fluid gravity-driven flow Heat source/sink Inclined heated plate

来源：评论

学校读者我要写书评

暂无评论

Integrating spheroid-on-a-chip with tubeless rocker platform: A high-throughput biological screening platform

引用

BIOTECHNOLOGY JOURNAL 2023年第10期18卷 e2200621页

作者： Kheiri, Sina Chen, Zhengkun Yakavets, Ilya Rakhshani, Faeze Young, Edmond W. K. Kumacheva, Eugenia Univ Toronto Dept Mech & Ind Engn Toronto ON Canada Univ Toronto Dept Chem 80 St George St Toronto ON M5P 2Y2 Canada Univ Toronto Inst Biomed Engn Toronto ON Canada Univ Toronto Dept Chem Engn & Appl Chem Toronto ON Canada

Spheroid-on-a-chip platforms are emerging as promising in vitro models that enable screening of the efficacy of biologically active ingredients. Generally, the supply of liquids to spheroids occurs in the steady flow mode with the use of syringe pumps;however, the utilization of tubing and connections, especially for multiplexing and high-throughput screening applications, makes spheroid-on-a-chip platforms labor- and cost-intensive. gravity-induced flow using rocker platforms overcomes these challenges. Here, a robust gravity-driven technique was developed to culture arrays of cancer cell spheroids and dermal fibroblast spheroids in a high-throughput manner using a rocker platform. The efficiency of the developed rocker-based platform was benchmarked to syringe pumps for generating multicellular spheroids and their use for screening biologically active ingredients. Cell viability, internal spheroid structure as well as the effect of vitamin C on spheroids' protein synthesis was studied. The rocker-based platform not only offers comparable or enhanced performance in terms of cell viability, spheroids formation, and protein production by dermal fibroblast spheroids but also, from a practical perspective, offers a smaller footprint, requires a lower cost, and offers an easier method for handling. These results support the application of rocker-based microfluidic spheroid-on-a-chip platforms for in vitro screening in a high-throughput manner with industrial scaling-up opportunities.

关键词： microfluidics organ-on-a-chip spheroid-on-a-chip gravity-driven flow multicellular spheroids high-throughput screening

来源：评论

学校读者我要写书评

暂无评论

flow Analysis of Multilayer gravity-driven Sisko Fluid over a Flat Inclined Plane

引用

ARABIAN JOURNAL FOR SCIENCE AND ENGINEERING 2019年第9期44卷 8081-8093页

作者： Chaudhuri, Sumanta Chakraborty, Paromita Das, Bitanjaya Singh, Ram Karan Kalinga Inst Ind Technol Sch Mech Engn Bhubaneswar 751024 India Kalinga Inst Ind Technol Sch Civil Engn Bhubaneswar 751024 India King Khalid Univ Dept Civil Engn Abha 61421 Saudi Arabia

gravity-driven thin film flow of two immiscible non-Newtonian Sisko fluids over a flat inclined plane is investigated. The equation, describing the flow, is nonlinear in nature and does not have a closed form of solution in general. In this study, the nonlinear governing differential equations are solved analytically by employing homotopy perturbation method (HPM). Besides, an exact solution for a special case of the non-Newtonian index is also obtained. The results of the solution based on HPM are compared with the exact solution for the special case, and it shows close agreement between the two results. This demonstrates the efficacy of HPM for solving nonlinear problems. The expression for the velocity is obtained, and the effects of various parameters like Sisko fluid parameters, density ratio, and viscosity ratio are also analyzed and discussed. The results indicate that with increase in the density ratio, it causes a significant increase in the velocity of fluids in both the layers and the velocities in both the layers are decreasing significantly with an increase in the Sisko fluid parameters. This study has got wider application in various industrial activities such as protective and decorative coating, painting.

关键词： gravity-driven flow Sisko fluid Thin film flow Homotopy perturbation method Multilayer flow

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：