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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 *** 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 *** 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 ***,a mathematical model of the velocity distribution at the flapper groove exit is established by using Schlichting velocity equations for incompressible laminar fluid ***,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 *** 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 *** verification of the theory is also *** 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

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 *** 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 *** hydraulic transients of the valve closing process are simulated using the model.A more reasonable attenuation of hydraulic transients is *** accurate attenuation is more distinct than that obtained from the traditional mathematical *** research shows that the hydraulic transient is a type of energy waves,and its attenuation is caused by the friction *** laminar friction resistance is more important than the turbulent friction resistance if the flow velocity is smaller than the critical *** the turbulent friction resistance is more *** laminar friction resistance is important in the attenuation of hydraulic transients for the closing ***,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

STUDIES ON THE LAW OF laminar HELICAL flow OF POWER-LAW FLUID IN ECCENTRIC ANNULI

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Applied Mathematics and Mechanics(English Edition) 1993年第7期14卷 627-634页

作者：李帮达刘永健张景富 Daqing Petroluem Institute Anda Helongjiang

The flow of mud under a constant axial pressure gradient in eccentric annuli was studied extensively in this paper. Assumed that the inner wall was rotating at a constant angular velocity, then the constitutive equation of power law fluid and the equation of motion were given. The expressions of apparent viscosity, velocity, flow rate and pressure loss were obtained. In Some numerical results were given by alternation-substitution method. The conclusions are that the viscosity difference between wide and narrow clearance is reduced with increasing the rotation of inner cylinder and/or decreasing the eccentric distance. The flow rate will be increased with increasing the rotation of inner cylinder and eccentric distance, etc.. The pressure loss in eccentric flow is quite large than in concentric axial flow. The results are useful for calculating hydraulic parameters in drilling engineering.

关键词： Confined flow laminar flow Well drilling

3-D NUMERICAL STUDY OF laminar AND TURBULENT flow INSIDE A 90-DEG-BEND SQUARE AND FLAT DUCT

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Journal of Hydrodynamics 1992年第4期4卷 97-108页

作者： Liu Qing-chao Chai Fang-Kun Chen Zhen-xi Institute of Water Conservancy and Hydroelectric Power Research,Beijing 100044,P.R.China

With the application of body-fitted coordinate method and the standard k-epsilon equations,the rtumericat sotution to the averaged N-S equations is *** and turbu- tent flows inside a 90-Deg-Bent duct are studied,yield... 详细信息

关键词： 3—D laminar flow turbulent flow

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 *** 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 *** 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 *** single-phase nanofluid model is utilized to describe convective heat transfer in hybrid nanofluids,incorporating the experimental *** 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 *** influence of variable fluid parameters on both swirling and non-swirling flow cases is ***,the Nusselt number for the disk surface is *** 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

Modeling Submicron Particles Collection in laminar Forced Convection Gas flow by a Rectangular Venturi Scrubber

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Open Journal of Air Pollution 2016年第1期5卷 10-26页

作者： Serge Wendsida Igo Kokou N’wuitcha Belkacem Zeghmati Xavier Chesneau Département Energie Institut de Recherche en Sciences Appliquées et Technologies (IRSAT/CNRST) Ouagadougou Burkina Faso GPTE-LES Département de Physique Université de Lomé Lomé Togo Laboratoire de Mathématiques et Physique des Systèmes (LAMPS) Perpignan France

Venturi scrubbers are usually used for large particles cleaning in turbulent gaseous flow. In this work, submicron particles scrubbing in laminar forced convection dusty air flow in a rectangular venturi scrubber have been numerically simulated. Hydrodynamics effects and scrubbing process are investigated in detail. Results are presented as flow velocity, axial pressure, streamlines pattern, particles and droplets mass fraction profile, and collect efficiency. They show that venturi scrubbers can be efficient for submicron particles scrubbing. In fact, a better collect efficiency is obtained at high particles-droplets residence time, high ratio droplets concentration/particles concentration, low venturi diameter ratioand low Reynolds numbers. There is a critical Reynolds number value for which the collect efficiency becomes very low and tends to be constant.

关键词： Venturi Scrubber Submicron Particles Diffusion laminar flow Collect Efficiency

CFD simulation of hydrodynamics and mixing performance in dual shaft eccentric mixers

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Chinese Journal of Chemical Engineering 2023年第10期62卷 297-309页

作者： Songsong Wang Xia Xiong Peiqiao Liu Qiongzhi Zhang Qian Zhang Changyuan Tao Yundong Wang Zuohua Liu School of Chemistry and Chemical Engineering Chongqing UniversityChongqing 400044China State Key Laboratory of Coal Mine Disaster Dynamics and Control Chongqing 400044China School of Mechanical and Transportation Engineering Chongqing UniversityChongqing 400044China Department of Chemical Engineering Tsinghua UniversityBeijing 100084China

This work aims to systematically study hydrodynamics and mixing characteristics of non-Newtonian fluid(carboxyl methyl cellulose,CMC)in dual shaft eccentric *** rheology was described by the power law rheological *** fluid dynamics was employed to simulate the velocity field and shear rate inside the stirred *** influence mechanism of the rotational modes,height difference between impellers,impeller eccentricities,and impeller types on the flow field have been well *** studied the performance of different dual-shaft eccentric mixers at the constant power input with its fluid velocity profiles,average shear strain rate,mixing time and mixing *** counter-rotation mode shows better mixing performance than co-rotation mode,and greater eccentricity can shorten mixing time on the basis of same stirred *** intensify the hydrodynamic interaction between impellers and enhance the overall mixing performance of the dual shaft eccentric mixers,it is critical to have a reasonable combination of impellers and an appropriate spatial position of impellers.

关键词： Dual shaft eccentric mixers Non-Newtonian fluid Mixing laminar flow Computational fluid dynamics

Improving shipboard electronics cooling system by optimizing the heat sinks configuration

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Journal of Ocean Engineering and Science 2022年第5期7卷 498-508页

作者： Hamid Maleki Mohammad Reza Safaei Arturo S.Leon Taseer Muhammad Truong Khang Nguyen Department of Mechanical Engineering Isfahan University of TechnologyIsfahan 84156-83111Iran Department of Mechanical Engineering Florida International UniversityMiamiFL 33174USA Department of Medical Research China Medical University HospitalChina Medical UniversityTaichungTaiwan Mechanical Engineering Department Faculty of EngineeringKing Abdulaziz UniversityJeddahSaudi Arabia Department of Civil and Environmental Engineering Florida International UniversityMiamiFL 33174USA Department of Mathematics College of SciencesKing Khalid UniversityAbha 61413Saudi Arabia Division of Computational Physics Institute for Computational ScienceTon Duc Thang UniversityHo Chi Minh CityVietnam Faculty of Electrical and Electronics Engineering Ton Duc Thang UniversityHo Chi Minh CityVietnam

With the increase of high-power electrical components in modern ships,especially fully electric ships with electric propulsion drive(EPD),the cooling of EPD electrical components has become particularly *** optimal configurations for heat sinks with high thermal efficiency plays an essential role in this regard.A new technique for improving the efficiency of heat sinks is the utilization of perforated *** study examined the effects of perforation geometry(shape and size)on laminar airflow flow and heat transfer characteristics over a perforated plate-fin heat ***-dimensional simulations were conducted using the finite-volume scheme based on the SIMPLE *** this research,the effects of perforation shape and size on various parameters,e.g.,total drag force,average Nusselt number,perforated fin efficiency(PFE),heat transfer performance enhancement(HTPE),and fin optimization factor(η)were *** results confirmed that at a specific heat transfer surface area for perforated fins,the highest efficiency is achieved by circular *** contrast,the square perforations due to geometric similarity to rectangular fins could reach the maximum ***,fins with square perforations could achieve the most optimal ***,results showed that for a constant perforations size,change in perforations shape improves HTPE,PFE,andηby more than 40%,45%,and 110%,***,by modifying perforations size for a specified shape,an increment of more than 35%,40%,and 150%is observed in HTPE,PFE,andη,respectively.

关键词： Forced convection laminar flow Perforated fin Plate-fin heat sink Nusselt number