2012 Vol. 33, No. 4

Display Method:
Time-Dependent MHD Couette Flow of a Rotating Fluid With Hall and Ion-Slip Currents
Basant K.Jha, Clement A.Apere
2012, 33(4): 379-389. doi: 10.3879/j.issn.1000-0887.2012.04.001
Abstract(1206) PDF(730)
The unsteady MHD Couette flow of an electrically conducting fluid in a rotating system was investigated taking Hall and ion-slip currents into consideration. The derived fundamental equations on the assumption of small magnetic Reynolds number were solved analytically by employing the well known Laplace transform technique. A unified closed form expressions for the velocity and the skin friction for the two different cases of the magnetic field being fixed to either the fluid or to the moving plate were obtained. The effects of the various parameters of the problem on the velocity and the skin friction were discussed through graphs. The result obtained revealed that the primary and the secondary velocities increases with Hall current. An increase in the ion-slip also led to an increases in the primary velocity but decreases the secondary velocity. It has also been shown that the combined effect of the rotation, Hall and ion-slip parameters determines the contribution of the secondary motion in the fluid flow.
Exact Solutions in Generalized Oldroyd-B Fluid
T.Hayat, Sahrish Zaib, S.Asghar, Awatif A.Hendi
2012, 33(4): 390-405. doi: 10.3879/j.issn.1000-0887.2012.04.002
Abstract(1115) PDF(830)
The influence of slip condition on the magnetohydrodynamic (MHD) and rotating flow of a generalized Oldroyd-B fluid occupying a porous space was investigated. Fractional calculus approach was used in the mathematical modeling. Three illustrative examples induced by plate oscillations and periodic pressure gradient were considered and the exact solutions in each case was derived. Comparison was provided between the results of slip and no-slip conditions. The influence of slip was highlighted on the velocity profile by displaying graphs.
Convective Heat Transfer From Two Rotating Circular Cylinders in Tandem Arrangement Using Lattice Boltzmann Method
Hasan Nemati, Mousa Farhadi, Kurosh Sedighi, Mohammad Mohammadi Pirouz, Nima Niksefat Abatari
2012, 33(4): 406-424. doi: 10.3879/j.issn.1000-0887.2012.04.003
Abstract(1324) PDF(733)
A numerical investigation of the two-dimensional laminar flow past two rotating circular cylinders in tandem arrangement using lattice Boltzmann method was conducted. The numerical strategy for dealing with curved and moving boundaries of second-order accuracy for velocity and temperature fields was used. The effects of variation of rotational speed ratio and different gap spacing were studied at Reynolds number of 100 and Prandtl number of 0.71. A various range of rotational speed ratio for four different gap spacing of 3, 1.5, 0.7 and 0.2 were investigated. Results show that, for the first cylinder lift and drag coefficients for large amounts of gap spacing are similar a single cylinder while for the second cylinder lift coefficient with increasing angular velocity for all gap spacing is descending but drag coefficient is ascending with the exception of gap spacing of 3. Results of the averaged periodic Nusselt number on the surface of cylinders show that for small distance between cylinders and low angular velocity, conduction is dominant mechanism of heat transfer but for large distance and high angular velocity convection is main mechanism of heat transfer.
Flow and Heat Transfer Over a Hyperbolic Stretching Sheet
A.Ahmad, S.Asghar
2012, 33(4): 425-433. doi: 10.3879/j.issn.1000-0887.2012.04.004
Abstract(1297) PDF(824)
The boundary layer flow and heat transfer analysis of an incompressible viscous fluid for a hyperbolically stretching sheet was presented. The analytical and numerical results were obtained using series expansion method and local nonsimilarity (LNS) methods respectively. Analytical and numerical results for skin friction and Nusselt number were calculated and compared with each other. The significant observation was that the momentum and thermal boundary layer thicknesses decrease as the distance from the leading edge increases. The well known solution of linear stretching was found as the leading order solution for the hyperbolic stretching.
Investigation of Tensile Deformation Behavior of PC, ABS and PC/ABS Blends From Low to High Strain Rates
YIN Zheng-nan, WANG Tie-jun
2012, 33(4): 434-443. doi: 10.3879/j.issn.1000-0887.2012.04.005
Abstract(1643) PDF(1998)
The objective of this paper is to experimentally study the tensile deformation behavior of the polycarbonate (PC), acrylonitrile-butadiene-styrene (ABS) and PC/ABS blends (with the blending ratio of PC to ABS being 80∶20, 60∶40, 50∶50 and 40∶60) from low to high strain rates. Using universal MTS-810 machine and split Hopkinson Tension bar (SHTB) testing system, the quasi-static and impact tension tests were carried out at room temperature. The curves of true stress and true strain were obtained and the deformation behavior of PC, ABS and PC/ABS blends were characterized in detail. And the effects of strain rate on the yield stress from low to high strain rates were described with a linear relationship.
A Coupled Thermo-Hygro-Mechanical Damage Model for Concrete Subjected to High Temperatures
2012, 33(4): 444-459. doi: 10.3879/j.issn.1000-0887.2012.04.006
Abstract(1232) PDF(814)
Based on theory of mixtures, a coupled thermo-hygro-mechanical damage model for concrete subjected to high temperatures was presented. Concrete was considered as a mixture composed of solid skeleton, liquid water, water vapor, dry air and dissolved air. The Macroscopic balance equations of the model consisted of the mass conservation equations of each component, the momentum and energy conservation equation of the whole medium mixture. The state equations and constitutive model used in the model were given. Four final governing equations were given in term of four primary variables, i.e. displacement components of soil skeleton, gas pressure, capillary pressure and temperature. The processes involved in the coupled model included evaporation, dehydration, heat and mass transfer, etc. Through the process of deformation failure and energy properties, mechanics damage evolution equations were established based on the principle of conversation of energy and Lemaitre equivalent strain assumption, and then the influence of thermal damage on mechanical property and mechanics damage evolution equations were considered.
Effects of Three-Phase-Lag on Two Temperature Generalized Thermoelasticity for an Infinite Medium With a Spherical Cavity
Sukla Banik, M.Kanoria
2012, 33(4): 460-474. doi: 10.3879/j.issn.1000-0887.2012.04.007
Abstract(1286) PDF(884)
The thermoelastic interaction for the three-phase-lag heat equation in an isotropic infinite elastic body with a spherical cavity was studied in the context of two temperature generalized thermoelasticity theory (2TT). The heat conduction equation in the theory of three-phase-lag was a hyperbolic partial differential equation with a fourth order derivative with respect to time. The medium was assumed initially quiescent. By using the Laplace transformation, the fundamental equations had been expressed in the form of a vector-matrix differential equation, which was then solved by state space approach. The general solution obtained was applied to a specific problem, when the boundary of the cavity was subjected to thermal loading (thermal shock and ramp type heating) and the mechanical loading. The inversion of the Laplace transform was carried out by the Fourier series expansion techniques. The numerical values of the physical quantity were computed for copper like material. Significant dissimilarities between two models (two temperature Green-Naghdi theory with energy dissipation (2TGNIII) and two temperature three-phase-lag model (2T3phase)) were shown graphically. The effect of two temperature and the ramping parameters were also studied.
Research on the 1∶2 Subharmonic Resonance and Bifurcation of the Nonlinear Rotor-Seal System
LI Zhong-gang, CHEN Yu-shu
2012, 33(4): 475-485. doi: 10.3879/j.issn.1000-0887.2012.04.008
Abstract(1141) PDF(795)
The 1∶2 subharmonic resonance of the labyrinth seals/rotor systems was investigated, which the low-frequency vibration of stream turbines could be caused by the gas exciting force in. The empirical parameters of gas exciting force of Muszynska model were obtained by using the results of Computational Fluid Dynamics (CFD). Based on multiple scale method, the 1∶2 subharmonic resonance response of the dynamic system was gained by truncating the system with three orders. The transition sets and the local bifurcations diagrams of the dynamics system were presented by employing singular theory analysis. Meanwhile, the existence conditions of subharmonic resonance non-zeros solutions of the dynamic system were obtained,which provides a new theoretical basis in recognizing and protecting the rotor from the subharmonic resonant failures in the turbine machinery.
Asymptotic Behaviors of the Solutions for Dissipative Quantum Zakharov Equations
GUO Yan-feng, GUO Bo-ling, LI Dong-long
2012, 33(4): 486-499. doi: 10.3879/j.issn.1000-0887.2012.04.009
Abstract(1200) PDF(721)
The dissipative quantum Zakharov equations were mainly studied. The existence and uniqueness of the solutions for dissipative quantum Zakharov equations were proved by the standard Galerkin approximation method on the basis of a priori estimates. Meanwhile, the asymptotic behavior of solutions and the global attractor which was constructed in energy space equipped with weak topology were also investigated.
Degenerate Scale Problem in Antiplane Elasticity or Laplace Equation for Contour Shapes of Triangles or Quadrilaterals
CHEN Yi-zhou
2012, 33(4): 500-512. doi: 10.3879/j.issn.1000-0887.2012.04.010
Abstract(1360) PDF(763)
Several solutions of the degenerate scale for shapes of triangles or quadrilaterals in an exterior boundary value problem of antiplane elasticity or Laplace equation were provided. The Schwarz-Christoffel mapping was used thoroughly. It is found that a complex potential with simple form in the mapping plane satisfies the vanishing displacement condition (or w=0) along the boundary of the unit circle when a dimension “R” reaches its critical value 1.  This means the degenerate size in the physical plane is also achieved. Finally, the degenerate scales can be evaluated from some particular integrals that depend on some parameters in the mapping function. A lot of numerical results of degenerate sizes for shapes of triangles or quadrilaterals are provided.