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Fluid Dynamics & Materials Processing 2023年第2期19卷 501-511页

作者： Shrikant Arunrao Thote Netra Pal Singh Department of Mechanical Engineering Oriental UniversityIndore453555India

The thermal behavior of pipes with a twisted tape inside(used to enhance heat transfer through the tube wall)is studied in the laminar flow regime.Oil is used as the work fluid with the corresponding Reynolds Number spanning the interval 200–2000.It is found that in such conditions the‘Nusselt Number’(Nu)gradually increases with reducing the tape twist ratio,whereas the friction factor is detrimentally affected by the presence of the tape(as witnessed by the comparison with the companion case where a plain tube is considered).In particular,it is shown that the heat transfer efficiency can be improved by nearly 69%if tape inserts with a relatively low twist ratio are used.On the basis of these findings,it is concluded that loose fit tape inserts are superior to tight fit tapes in terms of heat transfer and ease of replacement.

关键词： Friction factor laminar flow Nusselt Number trapezoidal-cut twisted tape

Study of hybrid nanofluid flow in a stationary cone-disk system with temperature-dependent fluid properties

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Applied Mathematics and Mechanics(English Edition) 2024年第4期45卷 677-694页

作者： A.S.JOHN B.MAHANTHESH G.LORENZINI Center for Mathematical Needs Department of MathematicsCHRIST(Deemed to be University)Karnataka 560029India School of Mathematical and Statistical Sciences The University of Texas Rio Grande ValleyTexas 78539U.S.A. Department of Engineering and Architecture University of ParmaParma 43124Italy

Cone-disk systems find frequent use such as conical diffusers,medical devices,various rheometric,and viscosimetry applications.In this study,we investigate the three-dimensional flow of a water-based Ag-Mg O hybrid nanofluid in a static cone-disk system while considering temperature-dependent fluid properties.How the variable fluid properties affect the dynamics and heat transfer features is studied by Reynolds's linearized model for variable viscosity and Chiam's model for variable thermal conductivity.The single-phase nanofluid model is utilized to describe convective heat transfer in hybrid nanofluids,incorporating the experimental data.This model is developed as a coupled system of convective-diffusion equations,encompassing the conservation of momentum and the conservation of thermal energy,in conjunction with an incompressibility condition.A self-similar model is developed by the Lie-group scaling transformations,and the subsequent self-similar equations are then solved numerically.The influence of variable fluid parameters on both swirling and non-swirling flow cases is analyzed.Additionally,the Nusselt number for the disk surface is calculated.It is found that an increase in the temperature-dependent viscosity parameter enhances heat transfer characteristics in the static cone-disk system,while the thermal conductivity parameter has the opposite effect.

关键词： hybrid nanofluid cone-disk system laminar flow variable fluid property Nusselt number

Existence of multiple solutions for the laminar flow in a porous channel with suction at both slowly expanding and contracting walls

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International Journal of Minerals,Metallurgy and Materials 2011年第4期18卷 494-501页

作者： Xin-hui Si Lian-cunZheng Xin-xin Zhang Ying Chao Applied Science School University of Science and Technology Beijing Beijing 100083 China Department of Mechanical Engineering University of Science and Technology Beijing Beijing 100083 China Chemical Defense Institute of the PLA Beijing 102205 China

The asymptotic behavior of solutions of a similarity equation for the laminar flow in a porous channel with suction at both expanding and contracting walls has been obtained by using a singular perturbation method. However, in the matching process, this solution neglects exponentially small terms. To take into account these exponentially small terms, a method involving the inclusion of exponentially small terms in a perturbation series was used to find two of the solutions analytically. The series involving the exponentially small terms and expansion ratio predicts dual solutions. Furthermore, the result indicates that the expansion ratio has much important influence on the solutions.

关键词： laminar flow porous channels multiple solutions singular perturbation method

Surface wettability and flow properties of non-metallic pipes in laminar flow

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Chinese Journal of Chemical Engineering 2020年第3期28卷 636-642页

作者： Hongyuan Qi Aiguo Liang Huayi Jiang Jianying Shi Nana Sun Yulong Wang College of Petroleum Engineering Xi'an Shiyou UniversityXi'an 710065China Shaanxi Key Laboratory of Advanced Stimulation Technology for Oil&Gas Reservoirs Xi'an Shiyou UniversityXi'an 710065China Karamay Hongshan Oilfield Co.Ltd. Karamay 834000China No.1 Production Plant Xinjiang Oilfield Branch CompanyKaramay 834000China

In this paper,three liquids flowing in five pipes with the same inner diameter of 14 mm were studied to determine the relationship between the surface wettability and flow properties in laminar flow(Re b 2000).This was motivated by oilfield observations of increased pressure drops in non-metallic pipes compared to those in metal pipes,which was contrary to expectations.A new expression for the frictional coefficient that considers the Reynolds number and contact angleθin laminar flow for non-metallic pipes was proposed based on the experimental results of single-phase flow using dimension and regression analyses.The solutions of the anomalous phenomenon were proposed from the perspectives of the pipe diameter,contact-angle difference,and the compatibility between flexible composite pipe and JLHW105 oil according to the new formula.The surprising finding was that the surface wettability could control the frictional resistance by the critical contact angle(39.9°)obtained at the same Reynolds number.If 0°bθ≤39.9°,the frictional coefficient increased as the contact angle increased.In contrast,if 39.9°bθb 180°,the frictional coefficient decreased with increasing contact angle.The influences of the pipe diameter and contactangle difference on the pressure drop difference of JLHW105 oil showed an inversely proportional relation.A series of materials and liquids were tested.The selection of pipe material for transporting a given fluid can be based on the contact angle,surface tension,and critical limit of the contact angle obtained.The research results are expected to provide some guidelines for the selection of the appropriate pipe material for a given set of fluids.

关键词： Wettability Contact angle Frictional coefficient Fluid mechanics laminar flow Petroleum

Analysis of pressure characteristics under laminar and turbulent flow states inside the pilot stage of a deflection flapper servo-valve:Mathematical modeling with CFD study and experimental validation

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Chinese Journal of Aeronautics 2020年第3期33卷 1107-1118页

作者： Bijan Krishna SAHA Songjing LI Xinbei LV Department of Fluid Control and Automation Harbin Institute of TechnologyHarbin 150001China

Electro-hydraulic servo-valves are widely used components in the mechanical industry,aerospace and aerodynamic devices which precisely control the airplane or missile wings.Due to the small size and complex structure in the pilot stage of deflection flapper servo-valves,accurate mathematical models for the flow and pressure characteristics have always been very difficult to be built.In this paper,mathematical models for the pilot stage of deflection flapper servo-valve are investigated to overcome some gaps between the theoretical formulation and overall performance of the valve by considering different flow states.Here,a mathematical model of the velocity distribution at the flapper groove exit is established by using Schlichting velocity equations for incompressible laminar fluid flow.Moreover,when the flow becomes turbulent,a mathematical model of pressure characteristics in the receiving ports is built on the basis of the assumption of the collision between the liquid and the jet as the impact of the jet on a moving block of fluid particles.To verify the analytical models for both laminar and turbulent flows,the pressure characteristics of the deflection flapper pilot stage are calculated and tested by using numerical simulation and experiment.Experimental verification of the theory is also presented.The computed numerical and analytical results show a good agreement with experimental data.

关键词： Computational fluid dynamics(CFD) Deflection flapper servovalve laminar flow Pressure characteristics Servo-valve Turbulent submerged jet

Analytical solution for laminar flow through leaky tube

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Applied Mathematics and Mechanics(English Edition) 2011年第1期32卷 69-74页

作者： M.GORJI M.ALIPANAH M.SHATERI E.FARNAD Department of Mechanical Engineering Babol University of Technology Water and Westwater Company

The laminar flow through a leaky tube is investigated, and the momentum and conservation of energy equations are solved analytically. By using the Hagen-Poiseuille velocity profile and defining unknown functions for the axial and radial velocity compo- nents, the pressure and mass transfer equations are obtained, and their profiles are plotted according to different parameters. The results indicate that the axial velocity, the radial velocity, the mass transfer parameter, and the pressure in the tube decrease as the fluid moves along the tube.

关键词： leaky tube permeability mass transfer laminar flow analytical solution

THEORETICAL ANALYSIS ON HYDRAULIC TRANSIENT RESULTED BY SUDDEN INCREASE OF INLET PRESSURE FOR laminar PIPELINE flow

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Applied Mathematics and Mechanics(English Edition) 2004年第6期25卷 672-678页

作者：邓松圣周绍骑廖振方邱正阳曾顺鹏 Department of Oil Supply Engineering Chongqing College of Logistic EngineeringChongqing 400016P.R.China Mechanical College Chongqing UniversityChongqing 400044P.R.ChinaDepartment of Oil Supply EngineeringChongqing College of Logistic EngineeringChongqing 400016P.R.China Mechanical College Chongqing UniversityChongqing 400044P.R.China

Hydraulic transient, which is resulted from sudden increase of inlet pressure for laminar pipeline flow, is studied. The partial differential equation, initial and boundary conditions for transient pressure were constructed, and the theoretical solution was obtained by variable-separation method. The partial differential equation, initial and boundary conditions for flow rate were obtained in accordance with the constraint correlation between flow rate and pressure while the transient flow rate distribution was also solved by variable-separation method. The theoretical solution conforms to numerical solution obtained by method of characteristics (MOC) very well.

关键词： laminar flow pipeline flow hydraulic transient theoretical solution

Attenuation analysis of hydraulic transients with laminar-turbulent flow alternations

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Applied Mathematics and Mechanics(English Edition) 2010年第10期31卷 1209-1216页

作者：万五一朱嵩胡云进 College of Civil Engineering and Architecture Zhejiang University

An improved compound mathematical model is established to simulate the attenuation of hydraulic transients with laminar-turbulent alternations,which usually occur when the pipeline flow velocity fluctuates near the critical velocity.The laminar friction resistance and the turbulent friction resistance are considered respectively in this model by applying different resistance schemes to the characteristics method of fluid transient analysis.The hydraulic transients of the valve closing process are simulated using the model.A more reasonable attenuation of hydraulic transients is obtained.The accurate attenuation is more distinct than that obtained from the traditional mathematical model.The research shows that the hydraulic transient is a type of energy waves,and its attenuation is caused by the friction resistance.The laminar friction resistance is more important than the turbulent friction resistance if the flow velocity is smaller than the critical velocity.Otherwise the turbulent friction resistance is more important.The laminar friction resistance is important in the attenuation of hydraulic transients for the closing process.Thus,it is significant to consider the different resistances separately to obtain more accurate attenuation of hydraulic transients.

关键词： fluid transient laminar flow turbulent flow method of characteristics

laminar FLUID flow IN HELICAL ELLIPTICAL PIPE

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Journal of Hydrodynamics 2000年第2期12卷 62-71页

作者： Zhang, Jinsuo Zhang, Benzhao Zhejiang Univ Hangzhou China

By means of an orthogonal curvilinear coordinate system and the solution of complete N-S equations, the flow in a helical elliptical duct was analyzed by the perturbation method. The first-order solutions of the stream function, the axial velocity and the velocity of secondary flow were obtained. The effects of torsion, curvature and axial pressure gradient on the secondary flow were discussed. The torsion has first-order effect on the secondary flow in a helical elliptical pipe, and the secondary flow is dominated by torsion when the axial pressure gradient is small. For increasing gradient the secondary flow is eventually dominated by the effect due to curvature. The fact that the torsion has no effect on fluid flow in a helical pipe with a circular cross section was also confirmed. The most important conclusion is that the flow in a helical elliptical pipe to the first order can be obtained as a combination of the flow in a toroidal pipe and the flow in a twisted pipe.

关键词： flow of fluids laminar flow Perturbation techniques Torsional stress

ANALYTIC SOLUTIONS OF INCOMPRESSIBLE laminar flow IN THE INLET REGION OF A PIPE

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Applied Mathematics and Mechanics(English Edition) 2004年第8期25卷 894-897页

作者：孟庆国 Department of Mathematical and Physical Sciences National Natural Science Foundation of China Beijing 100085 P.R.China

The laminar analytic solutions of velocities and pressure in the central zone of the inlet region of pipe flow are given under the condition of uniform inflow, based on the Navier-Stokes equations of incompressible vi... 详细信息

关键词： pipe flow laminar flow inlet region analytic solution