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Unsteady flow of viscoelastic fluid between two cylinders using fractional Maxwell model

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Acta Mechanica Sinica 2012年第2期28卷 274-280页

作者： Muhammad Jamil Constantin Fetecau Corina Fetecau Abdus Salam School of Mathematical Sciences GC UniversityLahorePakistan Department of Mathematics NED University of Engineering&TechnologyKarachi-75270Pakistan Department of Mathematics Technical University of IasiIasi-700050Romania Department of Theoretical Mechanics Technical University of IasiIasi-700050Romania

The unsteady flow of an incompressible fractional Maxwell fluid between two infinite coaxial cylinders is studied by means of integral transforms. The motion of the fluid is due to the inner cylinder that applies a time dependent tor- sional shear to the fluid. The exact solutions for velocity and shear stress are presented in series form in terms of some generalized functions. They can easily be particularized to give similar solutions for Maxwell and Newtonian fluids. Fi- nally, the influence of pertinent parameters on the fluid motion, as well as a comparison between models, is highlighted by graphical illustrations.

关键词： Maxwell fluid Fractional derivative Exact so- lutions Velocity field shear stress Laplace and Hankel transforms

Mean flow and turbulence structure of open channel flow with suspended vegetation

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Journal of Hydrodynamics 2020年第2期32卷 314-325页

作者： Qian Li Yu-hong Zeng Yu Bai State Key Laboratory of Water Resources and Hydropower Engineering Science Wuhan UniversityWuhan430072China

In combination with a channel bed,suspended vegetationin an open channel can alter flow structure and generate vertically asymmetric flow.This study investigated the mean flow and turbulence structure of an open channel with suspended vegetation through theoretical analysis and laboratory experiments.Three patterns of bionic leaves with different roughness were adopted to imitate suspended vegetation,and three-dimensional velocity field was measured by using an acoustic Doppler velocimeter.The measured data showed that the vertical profile of streamwise velocity obeys a two-power law and that the maximum velocity at the middle depth is close to the smooth boundary(i.e.,the channel bed in the experiment)under the combined action of vegetation cover and channel bed.shear stress is linearly distributed along the vertical axis,and the vertical profile of turbulence intensity obeys an exponential law.Then,a two-power law expression was adopted to predict the vertical profile of streamwise velocity.Theoretical models for the vertical distribution of shear stress and turbulence intensity were also established.The predicted results validated by measurements showed that the different magnitudes of vegetation cover and channel bed boundary roughness exert an obvious impact on flow structure.

关键词： Suspended vegetation streamwise velocity shear stress turbulence intensity boundary roughness

NUMERICAL AND EXPERIMENTAL INVESTIGATION OF FLOW OVER A SEMICIRCULAR WEIR

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Acta Mechanica Sinica 2002年第6期18卷 594-602页

作者：刘春嵘呼和敖德马文驹 Institute of Mechanics Chinese Academy of Sciences Beijing China 100080

The water flow over a semicircular weir is investigated numerically and experimentally in this paper. The numerical model solves the Reynolds equation for a mean flow field with thek-ε-turbulent model. To trace the motion of the free surface, the COF method with geometric reconstruction is employed. The velocity of the flow is measured by means of LDV technique. Four types of flow patterns, the position of the separation and reattachment point, the distribution of shear stress on the bed at downstream of the weir are presented and discussed. The numerical results agree well with the experiment data.

关键词： flow over semicircular weir numerical modeling VOF method shear stress LDV technique

ELECTRORHEOLOGICAL PROPERTIES OF TALC POWDER/SILICONE OIL SUSPENSIONS UNDER DC FIELDS

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Chinese Journal of Polymer Science 2007年第3期25卷 245-252页

作者： Hasim Yilmaz Ummihan Yilmaz Chemistry Department Sciences FacultyHarran University63190 OsmanbeySanliurfaTurkey Chemistry Department Sciences FacultyGazi University06500 TeknikokullarAnkaraTurkey

In this study, the electrorheological （ER） behavior of suspensions prepared from d50 = 2.4 lam talc powder, dispersed in insulating silicone oil （SO） medium was investigated. Sedimentation stabilities of suspensions （c = 5 wt%） prepared using these talc powder powders were determined to be 78 days. The ER activity of all the suspensions was observed to increase with increasing electric field strength, concentration and decreasing shear rate. The shear stress of talc powder suspensions increased linearly with increasing concentrations of the particles and with the applied electric field strength. Electric field viscosity of all the suspensions decreased sharply with increasing shear rate and showed a typical shear thinning non-Newtonian visco-elastic behavior. Effects of frequency on the ER activity of talc powder/SO system were also investigated.

关键词： Electrorheological fluids Talc powder/silicone oil suspensions shear stress

EXPERIMENTAL STUDY ON BED-LOAD SEDIMENT TRANSPORT IN IRREGULAR WAVE-CURRENT COEXISTENT FIELD

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Journal of Hydrodynamics 2000年第2期12卷 42-53页

作者： Wu, Yongsheng Qin, Chongren Hu, Mei Tianjin Univ Tianjin China

In order to evaluate bed-load sediment transport in an irregular wave-current coexistent field, a series of experiments were completed in laboratory with an irregularly oscillating tray, which is designed to simulate the irregular wave-current coexistent field. The initial motion of sediment and the rates of transport over flat horizontal bed were tested. Comparison between experimental results of initial motion and modified Shields curve indicates that the Shields curve is still valid for the case of irregular wave-current coexistent field. Analysis of flow regime shows that initial conditions fall within smooth-turbulent transitional region. The results of transport rate show that net sediment transport rate can be expressed approximately as the function of the maximum bottom shear stress and mean shear stress. A dimensionless formula is proposed on the basis of the mechanisms of waves erode sediments and tides transport sediments.

关键词： Flow of water Ocean currents Oscillations shear stress Water waves

ANALYSIS OF OSCILLATORY BLOOD FLOW IN VARYING-AREA ELASTIC VESSEL

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Journal of Hydrodynamics 2003年第6期15卷 16-24页

作者： Gong Ke-qin Biomechanics Laboratory Fudan University Shanghai 200433 Chinae-mail:jxegong 1981

In this paper, by solving the fundamental e-qualions of periodicallyoscillatory blood flow, the distributions of pressure gradient and blood velocity in varying-areae-lastic vessel were obtained, and then the wall shear stress and its gradient were calculated. Asan example, the pulsatile blood flow in human carotid was analyzed and the effects of vessel taperangle on the distribution of wall shear stress and its gradient were discussed in detail. Numercialresults show that the wall shear stress will enlarge when the taper angle increases. Meantime, nomatter whether the vessel is converging or diverging, with the increase of the absolute value oftaper angle, the amplitude of wall shear stress gradient will enlarge significantly.

关键词： elastic vessel shear stress taper angle carotid oscillatory flow

Hydromagnetic flow through uniform channel bounded by porous media

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Applied Mathematics and Mechanics(English Edition) 2011年第7期32卷 837-846页

作者： K.RAMAKRISHNAN K.SHAILENDHRA Department of Mathematics Sri Krishna College of Engineering and TechnologySugunapuramKuniamuthurCoimbatore 641008TamilnaduIndia Department of Mathematics Amirta School of EngineeringAmirta Vishwa VidyapeethamCoimbatore 641105TamilnaduIndia

The combined effects of the magnetic field, permeable walls, Darcy velocity, and slip parameter on the steady flow of a fluid in a channel of uniform width are studied. The fluid flowing in the channel is assumed to be homogeneous, incompressible, and Newtonian. Analytical solutions are constructed for the governing equations using Beavers-Joseph slip boundary conditions. Effects of the magnetic field, permeability, Darcy velocity, and slip parameter on the axial velocity, slip velocity, and shear stress are discussed in detail. It is shown that the Hartmann number, Darcy velocity, porous parameter, and slip parameter play a vital role in altering the flow and in turn the shear stress.

关键词： uniform channel permeable wall magnetic field slip velocitY shear stress

ANALYTICAL SOLUTION OF RESTRAINED TORSIONAL stressES AND DISPLACEMENT FOR RECTANGULAR- SECTION BOX BAR WITH HONTYCOMB CORE

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Applied Mathematics and Mechanics(English Edition) 2004年第7期25卷 779-785页

作者：张英世张行 Department of Flight Vehicle Design and Applied Mechanics

Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.

关键词： honeycomb structure constrain twist attenuation rectangular section box bar normal stress shear stress warping displacement

Free torsion of thin-walled structural members of open-and closed-sections

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Applied Mathematics and Mechanics(English Edition) 2014年第1期35卷 25-32页

作者： Long-yuan LI D.EASTERBROOK School of Marine Science and Engineering University of Plymouth

Free torsion of thin-walled structures of open- and closed-sections is a classical elastic mechanics problem, which, in literature, is often solved by the method of membrane analogy. The method of membrane analogy, however, can be only applied to structures of a single material. If the structure consists of both open- and closed-sections, the method of membrane analogy is difficult to be applied. In this paper, a new method is presented for solving the free torsion of thin-walled structures of open- and/or closed- sections with multiple materials. By utilizing a simple statically indeterminate concept, torsional equations are derived based on the equilibrium and compatibility conditions. The method presented here not only is very simple and easy to understand but also can be applied to thin-walled structures of combined open- and closed-sections with multiple materials.

关键词： torsion thin-walled open-section closed-section shear flow shear stress