This study discusses the magnetohydrodynamic nanofluid flow over an inclined permeable surface influenced by mixed convection, and Cattaeo-Christov heat flux. The heat transfer analysis is performed in the presence of...This study discusses the magnetohydrodynamic nanofluid flow over an inclined permeable surface influenced by mixed convection, and Cattaeo-Christov heat flux. The heat transfer analysis is performed in the presence of a heat source/sink and thermal stratification. To gauge the energy loss during the process, an irreversibility analysis is also performed. A numerical solution to the envisaged problem is obtained using the bvp4c package of MATLAB. Graphs are drawn to assess the consequences of the arising parameters against the associated profiles. The results show that an augmentation in the magnetic field and nanomaterial volume fraction results in an enhancement in the temperature profile. A strong magnetic field can significantly reduce the fluid velocity. The behavior of the Skin friction coefficient against the different estimates of emerging parameters is discussed. .展开更多
A lattice Boltzmann flux solver(LBFS)is presented for simulation of fluid flows.Like the conventional computational fluid dynamics(CFD)solvers,the new solver also applies the finite volume method to discretize the gov...A lattice Boltzmann flux solver(LBFS)is presented for simulation of fluid flows.Like the conventional computational fluid dynamics(CFD)solvers,the new solver also applies the finite volume method to discretize the governing differential equations,but the numerical flux at the cell interface is not evaluated by the smooth function approximation or Riemann solvers.Instead,it is evaluated from local solution of lattice Boltzmann equation(LBE)at cell interface.Two versions of LBFS are presented in this paper.One is to locally apply one-dimensional compressible lattice Boltzmann(LB)model along the normal direction to the cell interface for simulation of compressible inviscid flows with shock waves.The other is to locally apply multi-dimensional LB model at cell interface for simulation of incompressible viscous and inviscid flows.The present solver removes the drawbacks of conventional lattice Boltzmann method(LBM)such as limitation to uniform mesh,tie-up of mesh spacing and time interval,limitation to viscous flows.Numerical examples show that the present solver can be well applied to simulate fluid flows with non-uniform mesh and curved boundary.展开更多
Prediction of critical heat flux (CHF) in annular flow is important for the safety of once - through steam generator and the reactor core under accident conditions. The dryout in annular flow occurs at the point where...Prediction of critical heat flux (CHF) in annular flow is important for the safety of once - through steam generator and the reactor core under accident conditions. The dryout in annular flow occurs at the point where the film is depleted due to entrainment, deposition, and evaporation. The film thickness, film mass flow rate along axial distribution, and CHF are calculated in vertical upward round tube on the basis of a separated flow model of annular flow. The theoretical CHF values are higher than those derived from experimental data, with error being within 30%.展开更多
The transport properties in the mixed state of high-quality Ca_(0.8)La_(0.2)Fe_(0.98)Co_(0.02)As_2single crystal,a newly discovered 112-type iron pnictide superconductor,are comprehensively studied by magneto-resistiv...The transport properties in the mixed state of high-quality Ca_(0.8)La_(0.2)Fe_(0.98)Co_(0.02)As_2single crystal,a newly discovered 112-type iron pnictide superconductor,are comprehensively studied by magneto-resistivity measurement.The field-dependent activation energy,U_0,is derived in the framework of thermally activated flux flow(TAFF)theory,yielding a power law dependence U_0~H~αwith a crossover at a magnetic field around 2 T in both H⊥ab and H//ab,which is ascribed to the different pinning mechanisms.Moreover,we have clearly observed the vortex phase transition from vortex-glass to vortex-liquid according to the vortex-glass model,and vortex phase diagrams are constructed for both H⊥ab and H//ab.Finally,the results of mixed-state Hall effect show that no sign reversal of transverse resistivityρ_(xy)(H)is detected,indicating that the Hall component arising from the vortex flow is in theories or experiments previously reported on some high-T_ccuprates.展开更多
In this paper, the effect of non-uniform heat flux on heat transfer in boundary layer stagnation-point flow over a shrinking sheet is studied. The variable boundary heat fluxes are considered of two types: direct pow...In this paper, the effect of non-uniform heat flux on heat transfer in boundary layer stagnation-point flow over a shrinking sheet is studied. The variable boundary heat fluxes are considered of two types: direct power-law variation with the distance along the sheet and inverse power-law variation with the distance. The governing partial differential equations (PDEs) are transformed into non linear self-similar ordinary differential equations (ODEs) by similarity transformations, and then those are solved using very efficient shooting method. The direct variation and inverse variation of heat flux along the sheet have completely different effects on the temperature distribution. Moreover, the heat transfer characteristics in the presence of non-uniform heat flux for several values of physical parameters are also found to be interesting.展开更多
We further develop the lattice Boltzmann (LB) model [Physica A 382 (2007) 502] for compressible flows fromtwo aspects.Firstly,we modify the Bhatnagar-Gross-Krook (BGK) collision term in the LB equation,which makes the...We further develop the lattice Boltzmann (LB) model [Physica A 382 (2007) 502] for compressible flows fromtwo aspects.Firstly,we modify the Bhatnagar-Gross-Krook (BGK) collision term in the LB equation,which makes themodel suitable for simulating flows with different Prandtl numbers.Secondly,the flux limiter finite difference (FLFD)scheme is employed to calculate the convection term of the LB equation,which makes the unphysical oscillations atdiscontinuities be effectively suppressed and the numerical dissipations be significantly diminished.The proposed modelis validated by recovering results of some well-known benchmarks,including (i) The thermal Couette Row;(ii) One- andtwo-dimensional Riemann problems.Good agreements are obtained between LB results and the exact ones or previouslyreported solutions.The Rexibility,together with the high accuracy of the new model,endows the proposed modelconsiderable potential for tracking some long-standing problems and for investigating nonlinear nonequilibrium complexsystems.展开更多
A mathematical model of two-dimensional turbulent gas-particle two-phase flow based on the modified diffusion flux model (DFM) and a numerical simulation method to analyze the gas-particle flow structures are develope...A mathematical model of two-dimensional turbulent gas-particle two-phase flow based on the modified diffusion flux model (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux model, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by κ-ε-κp two-fluid model, which shows a reasonable agreement. It is confirmed that the modified diffusion flux model is suitable for simulating the multi-dimensional gas-particle two-phase flow.展开更多
In this paper the transient two-phase flow equations and their eigenvalues are first introduced. The flux vector is then split into subvectors which just contain a specially signed eigenvalue. Using one-sided spatial ...In this paper the transient two-phase flow equations and their eigenvalues are first introduced. The flux vector is then split into subvectors which just contain a specially signed eigenvalue. Using one-sided spatial difference operators finite difference equations and their solutions are obtained. Finally comparison with experiment shows the predicted results produce good agreement with experimental data.展开更多
In the present paper, Lie group symmetry method is used to obtain some exact solutions for a hyperbolic system of partial differential equations (PDEs), which governs an isothermal no-slip drift-flux model for multi...In the present paper, Lie group symmetry method is used to obtain some exact solutions for a hyperbolic system of partial differential equations (PDEs), which governs an isothermal no-slip drift-flux model for multiphase flow problem. Those sym- metries are used for the governing system of equations to obtain infinitesimal transforma- tions, which consequently reduces the governing system of PDEs to a system of ODEs. Further, the solutions of the system of ODEs which in turn produces some exact solutions for the PDEs are presented. Finally, the evolutionary behavior of weak discontinuity is discussed.展开更多
In this paper,a new flux limiter scheme with the splitting technique is successfully incorporated into amultiple-relaxation-time lattice Boltzmann (LB) model for shacked compressible Hows.The proposed flux limiter sch...In this paper,a new flux limiter scheme with the splitting technique is successfully incorporated into amultiple-relaxation-time lattice Boltzmann (LB) model for shacked compressible Hows.The proposed flux limiter schemeis efficient in decreasing the artificial oscillations and numerical diffusion around the interface.Due to the kinetic nature,some interface problems being difficult to handle at the macroscopic level can be modeled more naturally through theLB method.Numerical simulations for the Richtmyer-Meshkov instability show that with the new model the computedinterfaces are smoother and more consistent with physical analysis.The growth rates of bubble and spike present asatisfying agreement with the theoretical predictions and other numerical simulations.展开更多
This study sought to forecast water flow and sediment flux in the scheme as potential contributions for improved management in the Chókwè Irrigation Scheme (CIS). Fieldwork data was collected during dry (DS)...This study sought to forecast water flow and sediment flux in the scheme as potential contributions for improved management in the Chókwè Irrigation Scheme (CIS). Fieldwork data was collected during dry (DS) and wet (WS) seasons. Flow measurement was performed at 9 stations using a calibrated flow meter OTT C31. Water flow and sediment flux from 2004 to 2019 were used. Hydrodynamic forecast simulations were performed using Mann-Kendall test and ARIMA model for determination of temporal trends. Findings suggest higher values during DS for water discharge and sediment flux. Mann-Kendall test for sediment discharge trends was not significant at 95% significance level, except for the Offtake in WS. ARIMA test for the sediment discharges, at the Intake, for DS and WS, sediments were well described by the ARIMA model and gave a good result for the sediments. Good fit between the observed and the predicted ARIMA model was found. ARIMA model for sediment discharge at CIS based on AIC has a good fit for AR (p = 1), whereby, at the Intake the ARIMA p-value was 0.822 and 0.932, for WS and DS, respectively. Whilst in the Offtake, the ARIMA p-value was 0.877 and 0.893, respectively. These results can be used to improve the CIS management, both for water flow and sediment flux.展开更多
The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in...The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in pipelines. Presently, the method of characteristics is widely used to solve classical hydraulic transient problems. However, when it is used to solve coupling hydraulic transient problems, excessive interpolation errors may be introduced into the results due to unavoidable multiwave interpolated calculations. To deal with the problem, a finite difference scheme based on the Steger- Warming flux vector splitting is proposed. A flux vector splitting scheme is established for the coupling hydraulic transient model of gas-liquid-solid three-phase mixed flow in the pipelines. The flux subvectors are then discretized by the Lax-Wendroff central difference scheme and the Warming-Beam upwind difference scheme with second-order precision in both time and space. Under the Rankine-Hugoniot conditions and the corresponding boundary conditions, an effective solution to those points located at the boundaries is developed, which can avoid the problem beyond the calculation region directly induced by the second-order discrete technique. Numerical and experimental verifications indicate that the proposed scheme has several desirable advantages including high calculation precision, excellent shock wave capture capability without false numerical oscillation, low sensitivity to the Courant number, and good stability.展开更多
Unsteady MHD natural convective heat and mass transfer flow through a semi-infinite vertical porous plate in a rotating system have been investigated with the combined Soret and Dufour effects in the presence of Hall ...Unsteady MHD natural convective heat and mass transfer flow through a semi-infinite vertical porous plate in a rotating system have been investigated with the combined Soret and Dufour effects in the presence of Hall current and constant heat flux. It is considered that the porous plate is subjected to constant heat flux. The obtained non-dimensional, non-similar coupled non-linear and partial differential equations have been solved by explicit finite difference technique. Numerical solutions for velocities, temperature and concentration distributions are obtained for various parameters by the above mentioned technique. The local and average shear stresses, Nusselt number as well as Sherwood number are also investigated. The stability conditions and convergence criteria of the explicit finite difference scheme are established for finding the restriction of the values of various parameters to get more accuracy. The obtained results are illustrated with the help of graphs to observe the effects of various legitimate parameters.展开更多
The Cattaneo-Christov heat flux in the two-dimensional (2D) flow of a third- grade fluid towards an exponentially stretching sheet is investigated. The energy equation is considered through thermal relaxation. Simil...The Cattaneo-Christov heat flux in the two-dimensional (2D) flow of a third- grade fluid towards an exponentially stretching sheet is investigated. The energy equation is considered through thermal relaxation. Similarity transformations are accounted to obtain the ordinary differential systems. The converted non-dimensional equations are solved for the series solutions. The convergence analysis of the computed solutions is reported. The graphical results of the velocity and temperature profiles are plotted and elaborated in detail. The results show that the thermal relaxation enhances the temper- ature gradient while reduces the temperature profile.展开更多
Analytical solutions of temperature distributions and the Nusselt numbers in forced convection are reported for flow through infinitely long parallel plates, where the upper plate moves in the flow direction with cons...Analytical solutions of temperature distributions and the Nusselt numbers in forced convection are reported for flow through infinitely long parallel plates, where the upper plate moves in the flow direction with constant velocity and the lower plate is kept stationary. The flow is assumed to be laminar, both hydro-dynamically and thermally fully developed, taking into account the effect of viscous dissipation of the flowing fluid. Both the plates being kept at specified and at different constant heat fluxes are considered as thermal boundary conditions. The solutions obtained from energy equation are in terms of Brinkman number, dimensionless velocity and heat flux ratio. These parameters greatly influence and give complete understanding on heat transfer rates that has potentials for designing and analyzing energy equipment and processes.展开更多
Based on field observations carried out in August, 2008, we obtained a set of data on velocity, hydrography, and hydrochemistry in the Luzon Strait, with which the velocity structure of the area, especially in deep ch...Based on field observations carried out in August, 2008, we obtained a set of data on velocity, hydrography, and hydrochemistry in the Luzon Strait, with which the velocity structure of the area, especially in deep channels, was analyzed, and the material fluxes, including water, dissolved oxygen, and nutrients were calculated. The results indicate that a net eastward water flux of 7.0 Sv occurred through the Luzon Strait. The deep layer flux in the southern part, through the deep channel, was westward with a value of 1.9 Sv, which confirms that deep Pacific water flows into the South China Sea via the deep passage in the Luzon Strait. Accordingly, the net flux of dissolved oxygen was 13.2×105 mol/s, and the values for dissolved inorganic nitrogen, phosphate and silicate were 4.6×104 mol/s, 2.4×103 mol/s, and 8.9×104 mol/s, respectively. Detailed descriptions of these material fluxes in the upper layer, the upper-intermediate layer, the lower-intermediate layer, and the deep layer through the Luzon Strait are discussed. These results and interpretations highlight the importance of material exchanges between the South China Sea and the Pacific Ocean.展开更多
文摘This study discusses the magnetohydrodynamic nanofluid flow over an inclined permeable surface influenced by mixed convection, and Cattaeo-Christov heat flux. The heat transfer analysis is performed in the presence of a heat source/sink and thermal stratification. To gauge the energy loss during the process, an irreversibility analysis is also performed. A numerical solution to the envisaged problem is obtained using the bvp4c package of MATLAB. Graphs are drawn to assess the consequences of the arising parameters against the associated profiles. The results show that an augmentation in the magnetic field and nanomaterial volume fraction results in an enhancement in the temperature profile. A strong magnetic field can significantly reduce the fluid velocity. The behavior of the Skin friction coefficient against the different estimates of emerging parameters is discussed. .
基金Supported by the National Natural Science Foundation of China(11272153)
文摘A lattice Boltzmann flux solver(LBFS)is presented for simulation of fluid flows.Like the conventional computational fluid dynamics(CFD)solvers,the new solver also applies the finite volume method to discretize the governing differential equations,but the numerical flux at the cell interface is not evaluated by the smooth function approximation or Riemann solvers.Instead,it is evaluated from local solution of lattice Boltzmann equation(LBE)at cell interface.Two versions of LBFS are presented in this paper.One is to locally apply one-dimensional compressible lattice Boltzmann(LB)model along the normal direction to the cell interface for simulation of compressible inviscid flows with shock waves.The other is to locally apply multi-dimensional LB model at cell interface for simulation of incompressible viscous and inviscid flows.The present solver removes the drawbacks of conventional lattice Boltzmann method(LBM)such as limitation to uniform mesh,tie-up of mesh spacing and time interval,limitation to viscous flows.Numerical examples show that the present solver can be well applied to simulate fluid flows with non-uniform mesh and curved boundary.
文摘Prediction of critical heat flux (CHF) in annular flow is important for the safety of once - through steam generator and the reactor core under accident conditions. The dryout in annular flow occurs at the point where the film is depleted due to entrainment, deposition, and evaporation. The film thickness, film mass flow rate along axial distribution, and CHF are calculated in vertical upward round tube on the basis of a separated flow model of annular flow. The theoretical CHF values are higher than those derived from experimental data, with error being within 30%.
基金Foundation of China (Grant Nos. 11674054, and 11611140101)XiangZhou Xing was also sponsored by the Scientific Research Foundation of Graduate School of Southeast University (Grant No. YBJJ1621)
文摘The transport properties in the mixed state of high-quality Ca_(0.8)La_(0.2)Fe_(0.98)Co_(0.02)As_2single crystal,a newly discovered 112-type iron pnictide superconductor,are comprehensively studied by magneto-resistivity measurement.The field-dependent activation energy,U_0,is derived in the framework of thermally activated flux flow(TAFF)theory,yielding a power law dependence U_0~H~αwith a crossover at a magnetic field around 2 T in both H⊥ab and H//ab,which is ascribed to the different pinning mechanisms.Moreover,we have clearly observed the vortex phase transition from vortex-glass to vortex-liquid according to the vortex-glass model,and vortex phase diagrams are constructed for both H⊥ab and H//ab.Finally,the results of mixed-state Hall effect show that no sign reversal of transverse resistivityρ_(xy)(H)is detected,indicating that the Hall component arising from the vortex flow is in theories or experiments previously reported on some high-T_ccuprates.
基金the National Board for Higher Mathematics(NBHM),DAE,Mumbai,India
文摘In this paper, the effect of non-uniform heat flux on heat transfer in boundary layer stagnation-point flow over a shrinking sheet is studied. The variable boundary heat fluxes are considered of two types: direct power-law variation with the distance along the sheet and inverse power-law variation with the distance. The governing partial differential equations (PDEs) are transformed into non linear self-similar ordinary differential equations (ODEs) by similarity transformations, and then those are solved using very efficient shooting method. The direct variation and inverse variation of heat flux along the sheet have completely different effects on the temperature distribution. Moreover, the heat transfer characteristics in the presence of non-uniform heat flux for several values of physical parameters are also found to be interesting.
基金Supported by the Science Foundations of LCP and CAEP under Grant Nos. 2009A0102005 and 2009B0101012National Natural Science Foundation of China under Grant Nos. 11075021, 11074300, and 11074303+3 种基金National Basic Research Program (973 Program) under Grant No. 2007CB815105Fundamental Research Funds for the Central University under Grant No. 2010YS03Technology Support Program of LangFang under Grant Nos. 2010011029/30/31Science Foundation of NCIAE under Grant No. 2008-ky-13
文摘We further develop the lattice Boltzmann (LB) model [Physica A 382 (2007) 502] for compressible flows fromtwo aspects.Firstly,we modify the Bhatnagar-Gross-Krook (BGK) collision term in the LB equation,which makes themodel suitable for simulating flows with different Prandtl numbers.Secondly,the flux limiter finite difference (FLFD)scheme is employed to calculate the convection term of the LB equation,which makes the unphysical oscillations atdiscontinuities be effectively suppressed and the numerical dissipations be significantly diminished.The proposed modelis validated by recovering results of some well-known benchmarks,including (i) The thermal Couette Row;(ii) One- andtwo-dimensional Riemann problems.Good agreements are obtained between LB results and the exact ones or previouslyreported solutions.The Rexibility,together with the high accuracy of the new model,endows the proposed modelconsiderable potential for tracking some long-standing problems and for investigating nonlinear nonequilibrium complexsystems.
基金Special Funds for Major State Basic Research Projects of China(G1999022200)
文摘A mathematical model of two-dimensional turbulent gas-particle two-phase flow based on the modified diffusion flux model (DFM) and a numerical simulation method to analyze the gas-particle flow structures are developed. The modified diffusion flux model, in which the acceleration due to various forces is taken into account for the calculation of the diffusion velocity of particles, is applicable to the analysis of multi-dimensional gas-particle two-phase turbulent flow. In order to verify its accuracy and efficiency, the numerical simulation by DFM is compared with experimental studies and the prediction by κ-ε-κp two-fluid model, which shows a reasonable agreement. It is confirmed that the modified diffusion flux model is suitable for simulating the multi-dimensional gas-particle two-phase flow.
文摘In this paper the transient two-phase flow equations and their eigenvalues are first introduced. The flux vector is then split into subvectors which just contain a specially signed eigenvalue. Using one-sided spatial difference operators finite difference equations and their solutions are obtained. Finally comparison with experiment shows the predicted results produce good agreement with experimental data.
基金Project supported by the Ministry of Minority Affairs through UGC,Government of India(No.F1-17.1/2010/MANF-CHR-ORI-1839)the Industrial Consultancy,IIT Kharagpur(No.IIT/SRIC/ISIRD/2013-14)
文摘In the present paper, Lie group symmetry method is used to obtain some exact solutions for a hyperbolic system of partial differential equations (PDEs), which governs an isothermal no-slip drift-flux model for multiphase flow problem. Those sym- metries are used for the governing system of equations to obtain infinitesimal transforma- tions, which consequently reduces the governing system of PDEs to a system of ODEs. Further, the solutions of the system of ODEs which in turn produces some exact solutions for the PDEs are presented. Finally, the evolutionary behavior of weak discontinuity is discussed.
基金Supported by the Science Foundation of Laboratory of Computational Physics, Science Foundation of China Academy of Engineering Physics under Grant Nos. 2009A0102005, 2009B0101012National Basic Research Program of China under Grant No. 2007CB815105+1 种基金National Natural Science Foundation of China under Grant Nos. 11074300, 11075021, and 11074303the Fundamental Research Funds for the Central Universities under Grant No. 2010YS03
文摘In this paper,a new flux limiter scheme with the splitting technique is successfully incorporated into amultiple-relaxation-time lattice Boltzmann (LB) model for shacked compressible Hows.The proposed flux limiter schemeis efficient in decreasing the artificial oscillations and numerical diffusion around the interface.Due to the kinetic nature,some interface problems being difficult to handle at the macroscopic level can be modeled more naturally through theLB method.Numerical simulations for the Richtmyer-Meshkov instability show that with the new model the computedinterfaces are smoother and more consistent with physical analysis.The growth rates of bubble and spike present asatisfying agreement with the theoretical predictions and other numerical simulations.
文摘This study sought to forecast water flow and sediment flux in the scheme as potential contributions for improved management in the Chókwè Irrigation Scheme (CIS). Fieldwork data was collected during dry (DS) and wet (WS) seasons. Flow measurement was performed at 9 stations using a calibrated flow meter OTT C31. Water flow and sediment flux from 2004 to 2019 were used. Hydrodynamic forecast simulations were performed using Mann-Kendall test and ARIMA model for determination of temporal trends. Findings suggest higher values during DS for water discharge and sediment flux. Mann-Kendall test for sediment discharge trends was not significant at 95% significance level, except for the Offtake in WS. ARIMA test for the sediment discharges, at the Intake, for DS and WS, sediments were well described by the ARIMA model and gave a good result for the sediments. Good fit between the observed and the predicted ARIMA model was found. ARIMA model for sediment discharge at CIS based on AIC has a good fit for AR (p = 1), whereby, at the Intake the ARIMA p-value was 0.822 and 0.932, for WS and DS, respectively. Whilst in the Offtake, the ARIMA p-value was 0.877 and 0.893, respectively. These results can be used to improve the CIS management, both for water flow and sediment flux.
基金supported by the Natural Science Foundation Project of CQ CSTC (No. 2010BB7421)
文摘The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in pipelines. Presently, the method of characteristics is widely used to solve classical hydraulic transient problems. However, when it is used to solve coupling hydraulic transient problems, excessive interpolation errors may be introduced into the results due to unavoidable multiwave interpolated calculations. To deal with the problem, a finite difference scheme based on the Steger- Warming flux vector splitting is proposed. A flux vector splitting scheme is established for the coupling hydraulic transient model of gas-liquid-solid three-phase mixed flow in the pipelines. The flux subvectors are then discretized by the Lax-Wendroff central difference scheme and the Warming-Beam upwind difference scheme with second-order precision in both time and space. Under the Rankine-Hugoniot conditions and the corresponding boundary conditions, an effective solution to those points located at the boundaries is developed, which can avoid the problem beyond the calculation region directly induced by the second-order discrete technique. Numerical and experimental verifications indicate that the proposed scheme has several desirable advantages including high calculation precision, excellent shock wave capture capability without false numerical oscillation, low sensitivity to the Courant number, and good stability.
文摘Unsteady MHD natural convective heat and mass transfer flow through a semi-infinite vertical porous plate in a rotating system have been investigated with the combined Soret and Dufour effects in the presence of Hall current and constant heat flux. It is considered that the porous plate is subjected to constant heat flux. The obtained non-dimensional, non-similar coupled non-linear and partial differential equations have been solved by explicit finite difference technique. Numerical solutions for velocities, temperature and concentration distributions are obtained for various parameters by the above mentioned technique. The local and average shear stresses, Nusselt number as well as Sherwood number are also investigated. The stability conditions and convergence criteria of the explicit finite difference scheme are established for finding the restriction of the values of various parameters to get more accuracy. The obtained results are illustrated with the help of graphs to observe the effects of various legitimate parameters.
文摘The Cattaneo-Christov heat flux in the two-dimensional (2D) flow of a third- grade fluid towards an exponentially stretching sheet is investigated. The energy equation is considered through thermal relaxation. Similarity transformations are accounted to obtain the ordinary differential systems. The converted non-dimensional equations are solved for the series solutions. The convergence analysis of the computed solutions is reported. The graphical results of the velocity and temperature profiles are plotted and elaborated in detail. The results show that the thermal relaxation enhances the temper- ature gradient while reduces the temperature profile.
文摘Analytical solutions of temperature distributions and the Nusselt numbers in forced convection are reported for flow through infinitely long parallel plates, where the upper plate moves in the flow direction with constant velocity and the lower plate is kept stationary. The flow is assumed to be laminar, both hydro-dynamically and thermally fully developed, taking into account the effect of viscous dissipation of the flowing fluid. Both the plates being kept at specified and at different constant heat fluxes are considered as thermal boundary conditions. The solutions obtained from energy equation are in terms of Brinkman number, dimensionless velocity and heat flux ratio. These parameters greatly influence and give complete understanding on heat transfer rates that has potentials for designing and analyzing energy equipment and processes.
基金Supported by National Natural Science Foundation of China (Nos.40906004,40776005 and 40890153)National High Technology Research and Development Program of China (863 Program) (2008AA09A402)Polar Science Foundation of China (20080206)
文摘Based on field observations carried out in August, 2008, we obtained a set of data on velocity, hydrography, and hydrochemistry in the Luzon Strait, with which the velocity structure of the area, especially in deep channels, was analyzed, and the material fluxes, including water, dissolved oxygen, and nutrients were calculated. The results indicate that a net eastward water flux of 7.0 Sv occurred through the Luzon Strait. The deep layer flux in the southern part, through the deep channel, was westward with a value of 1.9 Sv, which confirms that deep Pacific water flows into the South China Sea via the deep passage in the Luzon Strait. Accordingly, the net flux of dissolved oxygen was 13.2×105 mol/s, and the values for dissolved inorganic nitrogen, phosphate and silicate were 4.6×104 mol/s, 2.4×103 mol/s, and 8.9×104 mol/s, respectively. Detailed descriptions of these material fluxes in the upper layer, the upper-intermediate layer, the lower-intermediate layer, and the deep layer through the Luzon Strait are discussed. These results and interpretations highlight the importance of material exchanges between the South China Sea and the Pacific Ocean.