To investigate the overall performance of reverse energy bypass scramjet,firstly a variable spe⁃cific heat method combined with a chemical balance calculation module for combustion products were used to es⁃tablish a b...To investigate the overall performance of reverse energy bypass scramjet,firstly a variable spe⁃cific heat method combined with a chemical balance calculation module for combustion products were used to es⁃tablish a benchmark scramjet performance evaluation model.Based on the test data of typical flying point of Mach 7 with the altitude of 29 km,the reliability of the model was verified.The deviations of parameters such as the to⁃tal pressure loss of combustor between the model and the test data were analyzed.Furtherly,an analytical method for post-combustion magnetohydrodynamic power generation was established;by embedding the above method into the overall performance evaluation model,performance prediction considering the power generation effect was realized.Finally,based on the above model,variety regulations of the inlet and the outlet parameters of the power generation channel and performance parameters including the engine specific impulse and the unit thrust under different enthalpy extraction ratios and load factors were analyzed.It could be concluded that the model can reliably predict the variations of key parameters.As the value of the load factor increases,the value of the conduc⁃tivity required to reach the specified enthalpy extraction ratio first decreases and then increases,which is approxi⁃mately parabolic.In order to reduce the demand for the gas conductivity for MHD power generation,the load fac⁃tor should be around 0.5.When the load factor is 0.4 and the magnetic induction intensity is 2.5 T,if the enthalpy extraction ratio reaches 0.5%,the engine specific impulse performance reduces about 3.58%.展开更多
In this paper,we develop a multi-scalar auxiliary variables(MSAV)scheme for the Cahn-Hilliard Magnetohydrodynamics system by introducing two scalar auxiliary variables(SAV).This scheme is linear,fully decoupled and un...In this paper,we develop a multi-scalar auxiliary variables(MSAV)scheme for the Cahn-Hilliard Magnetohydrodynamics system by introducing two scalar auxiliary variables(SAV).This scheme is linear,fully decoupled and unconditionally stable in energy.Subsequently,we provide a detailed implementation procedure for full decoupling.Thus,at each time step,only a series of linear differential equations with constant coefficients need to be solved.To validate the effectiveness of our approach,we conduct an error analysis for this first-order scheme.Finally,some numerical experiments are provided to verify the energy dissipation of the system and the convergence of the proposed approach.展开更多
In this paper,we consider an initial boundary value problem for the nonhomo-geneous heat-conducting magnetohydrodynamic fuids when the viscosityμ,magnetic dif-fusivity v and heat conductivity k depend on the temperat...In this paper,we consider an initial boundary value problem for the nonhomo-geneous heat-conducting magnetohydrodynamic fuids when the viscosityμ,magnetic dif-fusivity v and heat conductivity k depend on the temperature according to μ(0)=°,k(0)=08,v(0)=07,withα,>0,β≥0.We prove the global existence of a unique strong solution provided that ■ is suitably small.In addition,we also get some results of the large-time behavior and exponential decay estimates.展开更多
In this paper,we study the Cauchy problem of three-dimensional incompressible magnetohydrodynamics with almost symmetrical initial values in the cylindrical coordinates.Here the almost axisymmetric means that(■θu_(0...In this paper,we study the Cauchy problem of three-dimensional incompressible magnetohydrodynamics with almost symmetrical initial values in the cylindrical coordinates.Here the almost axisymmetric means that(■θu_(0)^(r),■θeu_(0)^(θ),■θeu_(θ)^(z))is small.With additional smallness assumption on(u_(0)^(θ),b_(0)^(θ)),we prove the global existence of a unique strong solution(u,b),which keeps close to some axisymmetric vector fields.Moreover,we give the initial data with some special symmetric structures that will persist for all time.展开更多
We present a hybrid smoothed particle magnetohydrodynamics(SPMHD)code integrating smoothed particle hydrodynamics(SPH)and finite element methods(FEM)to simulate coupled fluid-electromagnetic phenomena.The framework em...We present a hybrid smoothed particle magnetohydrodynamics(SPMHD)code integrating smoothed particle hydrodynamics(SPH)and finite element methods(FEM)to simulate coupled fluid-electromagnetic phenomena.The framework employs SPH for fluid dynamics,addressing large deformations,shocks,and plasma behavior,while FEM resolves electromagnetic fields via Maxwell's equations for magnetic vector and electric scalar potentials,ensuring divergence-free conditions and global current density calculations in conductive region.Operator splitting method couples these modules,enabling real-time integration of magnetic,electric,thermal,and fluid fields.Benchmark tests validate the code against analytical solutions and existing models,including blow-by instability simulations that demonstrate the method's accuracy in capturing fluid-magnetic interactions.Designed for 3D applications,SPMHD offers robust scalability across multiprocessor architectures,establishing it as a versatile tool for plasma physics research.展开更多
Fluid flow through porous spaces with variable porosity has wide-range applications,notably in biomedical and thermal engineering,where it plays a vital role in comprehending blood flow dynamics within cardiovascular ...Fluid flow through porous spaces with variable porosity has wide-range applications,notably in biomedical and thermal engineering,where it plays a vital role in comprehending blood flow dynamics within cardiovascular systems,heat transfer and thermal management systems improve efficiency using porous materials with variable porosity.Keeping these important applications in view,in current study blood-based hybrid nanofluid flow has considered on a convectively heated sheet.The sheet exhibits the properties of a porous medium with variable porosity and extends in both the x and y directions.Blood has used as base fluid in which the nanoparticles of Cu and Cu O have been mixed.Thermal radiation,space-dependent,and thermal-dependent heat sources have been incorporated into the energy equation,while magnetic effects have been integrated into the momentum equations.Dimensionless variables have employed to transform the modeled equations into dimensionless form and facilitating their solution using bvp4c approach.It has concluded in this study that,both the primary and secondary velocities augmented with upsurge in variable porous factor and declined with escalation in stretching ratio,Casson,magnetic,and slip factors along x-and y-axes.Thermal distribution has grown up with upsurge in Casson factor,magnetic factor,thermal Biot number,and thermal/space-dependent heat sources while has retarded with growth in variable porous and stretching ratio factors.The findings of this investigation have been compared with the existing literature,revealing a strong agreement among present and established results that ensured the validation of the model and method used in this work.展开更多
The effect of magnetohydrodynamic(MHD)plasma actuators on the control of hypersonic shock wave/turbulent boundary layer interactions is investigated here using Reynolds-averaged Navier-Stokes calculations with low mag...The effect of magnetohydrodynamic(MHD)plasma actuators on the control of hypersonic shock wave/turbulent boundary layer interactions is investigated here using Reynolds-averaged Navier-Stokes calculations with low magnetic Reynolds number approximation.A Mach 5 oblique shock/turbulent boundary layer interaction was adopted as the basic configuration in this numerical study in order to assess the effects of flow control using different combinations of magnetic field and plasma.Results show that just the thermal effect of plasma under experimental actuator parameters has no significant impact on the flow field and can therefore be neglected.On the basis of the relative position of control area and separation point,MHD control can be divided into four types and so effects and mechanisms might be different.Amongst these,D-type control leads to the largest reduction in separation length using magnetically-accelerated plasma inside an isobaric dead-air region.A novel parameter for predicting the shock wave/turbulent boundary layer interaction control based on Lorentz force acceleration is then proposed and the controllability of MHD plasma actuators under different MHD interaction parameters is studied.The results of this study will be insightful for the further design of MHD control in hypersonic vehicle inlets.展开更多
In this research effort,numerical simulation of two-dimensional magnetohydrodynamic（MHD） channel is performed and Hall effect is studied.The computational model consists of the Navier-Stokes（N-S） equations coupled...In this research effort,numerical simulation of two-dimensional magnetohydrodynamic（MHD） channel is performed and Hall effect is studied.The computational model consists of the Navier-Stokes（N-S） equations coupled with electrical-magnetic source terms,Maxwell equations and the generalized Ohm＇s law.Boundary conditions for the electrical potential equation considering Hall effect are derived.To start with,the MHD channel with single-pair electrodes is studied and flow of the electric current is in accordance with physical principle.Then the MHD channel with five-pair electrodes is numerically simulated.The results show that the electrical current concentrates on the downstream of the anode and the upstream of the cathode due to Hall effect,and the flow field becomes asymmetrical.At the current value of the magnetic interaction parameter,the electrical-magnetic force affects the flow remarkably,decreasing the outlet Mach number and increasing the outlet pressure;what＇s more,the flow structure in the channel becomes extremely complex.Performances of MHD channels with continual electrodes and segmented electrodes are compared.The results show that performance of the MHD channel with segmented electrodes is better than that with continual electrodes with the increase of Hall parameter.展开更多
We conduct an electron magnetohydrodynamics magnetic reconnection experiment with guide-field in our Keda linear magnetized plasma device, in which two pulsed currents with the same direction are conducted in parallel...We conduct an electron magnetohydrodynamics magnetic reconnection experiment with guide-field in our Keda linear magnetized plasma device, in which two pulsed currents with the same direction are conducted in parallel with the axial direction of the main chamber of the device using two long aluminum sticks. After approximately 5μs, an X-type magnetic field line topology is formed at the center of the chamber. With the formation of the X-type topology of magnetic field lines, we can also find the rapid increase of the current and ratio of the common flux to the private flux in this area. Additionally, a reduction in the plasma density and the plasma density concentration along one pair of separatrices can also be found.展开更多
In this article, regularity criteria for the 3D magnetohydrodynamic equations are investigated. Some sufficient integrability conditions on two components or the gradient of two components of u ＋ B and u - B in Morre...In this article, regularity criteria for the 3D magnetohydrodynamic equations are investigated. Some sufficient integrability conditions on two components or the gradient of two components of u ＋ B and u - B in Morrey-Campanato spaces are obtained.展开更多
Multi-channel soft x-ray （SX） detectors are applied to generate images of magnetohydrodynamic （MHD） oscillation on the HT-7 tokamak, and the data from SX cameras are analysed by using the Fourier-Bessel harmonic r...Multi-channel soft x-ray （SX） detectors are applied to generate images of magnetohydrodynamic （MHD） oscillation on the HT-7 tokamak, and the data from SX cameras are analysed by using the Fourier-Bessel harmonic reconstruction method and the singular value decomposition. The image reconstruction of SX emissivity is obtained on the assumption of plasma rigid rotation, One of the important phenomena in the HT-7 discharge is the transition from the sawtooth oscillations to the MHD oscillations when the plasma density grows higher. The MHD structure observed in the SX tomography is featured as follows： the magnetic surface of MHD structure is made up of the crescent-shaped ＂hot core＂ and the circular ＂cold bubble＂. The structure of the magnetic surface is relatively stable. It rotates in the direction of the electron diamagnetic drift at a frequency being the oscillation frequency of the MHD oscillations.展开更多
The incompressible limit of the non-isentropic magnetohydrodynamic equations with zero thermal coefficient, in a two dimensional bounded domain with the Dirichlet condi- tion for velocity and perfectly conducting boun...The incompressible limit of the non-isentropic magnetohydrodynamic equations with zero thermal coefficient, in a two dimensional bounded domain with the Dirichlet condi- tion for velocity and perfectly conducting boundary condition for magnetic field, is rigorously justified.展开更多
The present paper is concerned with a class of ex- act solutions to the steady Navier-Stokes equations for the incompressible Newtonian viscous electrically conducting fluid flow due to a porous disk rotating with a c...The present paper is concerned with a class of ex- act solutions to the steady Navier-Stokes equations for the incompressible Newtonian viscous electrically conducting fluid flow due to a porous disk rotating with a constant angu- lar speed. The three-dimensional hydromagnetic equations of motion are treated analytically to obtained exact solutions with the inclusion of suction and injection. The well-known thinning/thickening flow field effect of the suction/injection is better understood from the constructed closed form veloc- ity equations. Making use of this solution, analytical formu- las for the angular velocity components as well as for the permeable wall shear stresses are derived. Interaction of the resolved flow field with the surrounding temperature is fur- ther analyzed via the energy equation. The temperature field is shown to accord with the dissipation and the Joule heating. As a result, exact formulas are obtained for the temperature field which take different forms corresponding to the condi- tion of suction or injection imposed on the wall.展开更多
The interaction between a converging cylindrical shock and double density interfaces in the presence of a saddle magnetic field is numerically investigated within the framework of ideal magnetohydrodynamics.Three flui...The interaction between a converging cylindrical shock and double density interfaces in the presence of a saddle magnetic field is numerically investigated within the framework of ideal magnetohydrodynamics.Three fluids of differing densities are initially separated by the two perturbed cylindrical interfaces.The initial incident converging shock is generated from a Riemann problem upstream of the first interface.The effect of the magnetic field on the instabilities is studied through varying the field strength.It shows that the Richtmyer-Meshkov and Rayleigh-Taylor instabilities are mitigated by the field,however,the extent of the suppression varies on the interface which leads to non-axisymmetric growth of the perturbations.The degree of asymmetry of the interfacial growth rate is increased when the seed field strength is increased.展开更多
Based on local algorithms,some parallel finite element(FE)iterative methods for stationary incompressible magnetohydrodynamics(MHD)are presented.These approaches are on account of two-grid skill include two major phas...Based on local algorithms,some parallel finite element(FE)iterative methods for stationary incompressible magnetohydrodynamics(MHD)are presented.These approaches are on account of two-grid skill include two major phases:find the FE solution by solving the nonlinear system on a globally coarse mesh to seize the low frequency component of the solution,and then locally solve linearized residual subproblems by one of three iterations(Stokes-type,Newton,and Oseen-type)on subdomains with fine grid in parallel to approximate the high frequency component.Optimal error estimates with regard to two mesh sizes and iterative steps of the proposed algorithms are given.Some numerical examples are implemented to verify the algorithm.展开更多
This paper studies stratified magnetohydrodynamic （MHD） flow of tan- gent hyperbolic nanofluid past an inclined exponentially stretching surface. The flow is subjected to velocity, thermal, and solutal boundary cond...This paper studies stratified magnetohydrodynamic （MHD） flow of tan- gent hyperbolic nanofluid past an inclined exponentially stretching surface. The flow is subjected to velocity, thermal, and solutal boundary conditions. The partial differential systems are reduced to ordinary differential systems using appropriate transformations. The reduced systems are solved for convergent series solutions. The velocity, temperature, and concentration fields are discussed for different physical parameters. The results indi- cate that the temperature and the thermal boundary layer thickness increase noticeably for large values of Brownian motion and thermophoresis effects. It is also observed that the buoyancy parameter strengthens the velocity field, showing a decreasing behavior of temperature and nanoparticle volume fraction profiles.展开更多
To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to ...To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.展开更多
In this analysis,the magnetohydrodynamic boundary layer flow of Casson fluid over a permeable stretching/shrinking sheet in the presence of wall mass transfer is studied.Using similarity transformations,the governing ...In this analysis,the magnetohydrodynamic boundary layer flow of Casson fluid over a permeable stretching/shrinking sheet in the presence of wall mass transfer is studied.Using similarity transformations,the governing equations are converted to an ordinary differential equation and then solved analytically.The introduction of a magnetic field changes the behavior of the entire flow dynamics in the shrinking sheet case and also has a major impact in the stretching sheet case.The similarity solution is always unique in the stretching case,and in the shrinking case the solution shows dual nature for certain values of the parameters.For stronger magnetic field,the similarity solution for the shrinking sheet case becomes unique.展开更多
Magnetohydrodynamic(MHD)instabilities are widely observed during tokamak plasma operation.Magnetic diagnostics provide important information which supports the understanding and control of MHD instabilities.This paper...Magnetohydrodynamic(MHD)instabilities are widely observed during tokamak plasma operation.Magnetic diagnostics provide important information which supports the understanding and control of MHD instabilities.This paper presents the current status of the magnetic diagnostics dedicated to measuring MHD instabilities at the J-TEXT tokamak;the diagnostics consist of five Mirnov probe arrays for measuring high-frequency magnetic perturbations and two saddle-loop arrays for low-frequency magnetic perturbations,such as the locked mode.In recent years,several changes have been made to these arrays.The structure of the probes in the poloidal Mirnov arrays has been optimized to improve their mechanical strength,and the number of in-vessel saddle loops has also been improved to support better spatial resolution.Due to the installation of high-field-side(HFS)divertor targets in early 2019,some of the probes were removed,but an HFS Mirnov array was designed and installed behind the targets.Owing to its excellent toroidal symmetry,the HFS Mirnov array has,for the first time at J-TEXT,provided valuable new information about the locked mode and the quasi-static mode(QSM)in the HFS.Besides,various groups of magnetic diagnostics at different poloidal locations have been systematically used to measure the QSM,which confirmed the poloidal mode number m and the helical structure of the QSM.By including the HFS information,the 2/1 resonant magnetic perturbation(RMP)-induced locked mode was measured to have a poloidal mode number m of~2.展开更多
文摘To investigate the overall performance of reverse energy bypass scramjet,firstly a variable spe⁃cific heat method combined with a chemical balance calculation module for combustion products were used to es⁃tablish a benchmark scramjet performance evaluation model.Based on the test data of typical flying point of Mach 7 with the altitude of 29 km,the reliability of the model was verified.The deviations of parameters such as the to⁃tal pressure loss of combustor between the model and the test data were analyzed.Furtherly,an analytical method for post-combustion magnetohydrodynamic power generation was established;by embedding the above method into the overall performance evaluation model,performance prediction considering the power generation effect was realized.Finally,based on the above model,variety regulations of the inlet and the outlet parameters of the power generation channel and performance parameters including the engine specific impulse and the unit thrust under different enthalpy extraction ratios and load factors were analyzed.It could be concluded that the model can reliably predict the variations of key parameters.As the value of the load factor increases,the value of the conduc⁃tivity required to reach the specified enthalpy extraction ratio first decreases and then increases,which is approxi⁃mately parabolic.In order to reduce the demand for the gas conductivity for MHD power generation,the load fac⁃tor should be around 0.5.When the load factor is 0.4 and the magnetic induction intensity is 2.5 T,if the enthalpy extraction ratio reaches 0.5%,the engine specific impulse performance reduces about 3.58%.
基金Research Project Supported by Shanxi Scholarship Council of China(2021-029)International Cooperation Base and Platform Project of Shanxi Province(202104041101019)Basic Research Plan of Shanxi Province(202203021211129)。
文摘In this paper,we develop a multi-scalar auxiliary variables(MSAV)scheme for the Cahn-Hilliard Magnetohydrodynamics system by introducing two scalar auxiliary variables(SAV).This scheme is linear,fully decoupled and unconditionally stable in energy.Subsequently,we provide a detailed implementation procedure for full decoupling.Thus,at each time step,only a series of linear differential equations with constant coefficients need to be solved.To validate the effectiveness of our approach,we conduct an error analysis for this first-order scheme.Finally,some numerical experiments are provided to verify the energy dissipation of the system and the convergence of the proposed approach.
基金supported by the National Natural Science Foundation of China(No.11931013)the Natural Science Foundation of Guangxi Province(No.2022GXNSFDA035078)the Foundamental Research Funds for the Central Universities,CHD(No.300102122115).
文摘In this paper,we consider an initial boundary value problem for the nonhomo-geneous heat-conducting magnetohydrodynamic fuids when the viscosityμ,magnetic dif-fusivity v and heat conductivity k depend on the temperature according to μ(0)=°,k(0)=08,v(0)=07,withα,>0,β≥0.We prove the global existence of a unique strong solution provided that ■ is suitably small.In addition,we also get some results of the large-time behavior and exponential decay estimates.
基金supported by the National Natural Science Foundation of China(11871305).
文摘In this paper,we study the Cauchy problem of three-dimensional incompressible magnetohydrodynamics with almost symmetrical initial values in the cylindrical coordinates.Here the almost axisymmetric means that(■θu_(0)^(r),■θeu_(0)^(θ),■θeu_(θ)^(z))is small.With additional smallness assumption on(u_(0)^(θ),b_(0)^(θ)),we prove the global existence of a unique strong solution(u,b),which keeps close to some axisymmetric vector fields.Moreover,we give the initial data with some special symmetric structures that will persist for all time.
基金supported by the Major National Science and Technology Infrastructure(No.2208-000000-04-01249628)the Shanghai Science and Technology Commission(No.21DZ1206500)。
文摘We present a hybrid smoothed particle magnetohydrodynamics(SPMHD)code integrating smoothed particle hydrodynamics(SPH)and finite element methods(FEM)to simulate coupled fluid-electromagnetic phenomena.The framework employs SPH for fluid dynamics,addressing large deformations,shocks,and plasma behavior,while FEM resolves electromagnetic fields via Maxwell's equations for magnetic vector and electric scalar potentials,ensuring divergence-free conditions and global current density calculations in conductive region.Operator splitting method couples these modules,enabling real-time integration of magnetic,electric,thermal,and fluid fields.Benchmark tests validate the code against analytical solutions and existing models,including blow-by instability simulations that demonstrate the method's accuracy in capturing fluid-magnetic interactions.Designed for 3D applications,SPMHD offers robust scalability across multiprocessor architectures,establishing it as a versatile tool for plasma physics research.
基金supported via funding from Prince Sattam bin Abdulaziz University(Grant No.PSAU/2024/R/1446)。
文摘Fluid flow through porous spaces with variable porosity has wide-range applications,notably in biomedical and thermal engineering,where it plays a vital role in comprehending blood flow dynamics within cardiovascular systems,heat transfer and thermal management systems improve efficiency using porous materials with variable porosity.Keeping these important applications in view,in current study blood-based hybrid nanofluid flow has considered on a convectively heated sheet.The sheet exhibits the properties of a porous medium with variable porosity and extends in both the x and y directions.Blood has used as base fluid in which the nanoparticles of Cu and Cu O have been mixed.Thermal radiation,space-dependent,and thermal-dependent heat sources have been incorporated into the energy equation,while magnetic effects have been integrated into the momentum equations.Dimensionless variables have employed to transform the modeled equations into dimensionless form and facilitating their solution using bvp4c approach.It has concluded in this study that,both the primary and secondary velocities augmented with upsurge in variable porous factor and declined with escalation in stretching ratio,Casson,magnetic,and slip factors along x-and y-axes.Thermal distribution has grown up with upsurge in Casson factor,magnetic factor,thermal Biot number,and thermal/space-dependent heat sources while has retarded with growth in variable porous and stretching ratio factors.The findings of this investigation have been compared with the existing literature,revealing a strong agreement among present and established results that ensured the validation of the model and method used in this work.
基金Project supported by the National Key R&D Program of China(Nos.2019YFA0405300 and 2019YFA0405203)the Chinese Scholarship Council(CSC)(No.201903170195)。
文摘The effect of magnetohydrodynamic(MHD)plasma actuators on the control of hypersonic shock wave/turbulent boundary layer interactions is investigated here using Reynolds-averaged Navier-Stokes calculations with low magnetic Reynolds number approximation.A Mach 5 oblique shock/turbulent boundary layer interaction was adopted as the basic configuration in this numerical study in order to assess the effects of flow control using different combinations of magnetic field and plasma.Results show that just the thermal effect of plasma under experimental actuator parameters has no significant impact on the flow field and can therefore be neglected.On the basis of the relative position of control area and separation point,MHD control can be divided into four types and so effects and mechanisms might be different.Amongst these,D-type control leads to the largest reduction in separation length using magnetically-accelerated plasma inside an isobaric dead-air region.A novel parameter for predicting the shock wave/turbulent boundary layer interaction control based on Lorentz force acceleration is then proposed and the controllability of MHD plasma actuators under different MHD interaction parameters is studied.The results of this study will be insightful for the further design of MHD control in hypersonic vehicle inlets.
文摘In this research effort,numerical simulation of two-dimensional magnetohydrodynamic（MHD） channel is performed and Hall effect is studied.The computational model consists of the Navier-Stokes（N-S） equations coupled with electrical-magnetic source terms,Maxwell equations and the generalized Ohm＇s law.Boundary conditions for the electrical potential equation considering Hall effect are derived.To start with,the MHD channel with single-pair electrodes is studied and flow of the electric current is in accordance with physical principle.Then the MHD channel with five-pair electrodes is numerically simulated.The results show that the electrical current concentrates on the downstream of the anode and the upstream of the cathode due to Hall effect,and the flow field becomes asymmetrical.At the current value of the magnetic interaction parameter,the electrical-magnetic force affects the flow remarkably,decreasing the outlet Mach number and increasing the outlet pressure;what＇s more,the flow structure in the channel becomes extremely complex.Performances of MHD channels with continual electrodes and segmented electrodes are compared.The results show that performance of the MHD channel with segmented electrodes is better than that with continual electrodes with the increase of Hall parameter.
基金Supported by the National Natural Science Foundation of China under Grant Nos 41331067 and 41527804the Key Research Program of Frontier Sciences of Chinese Academy of Sciences under Grant No QYZDJ-SSW-DQC010the Fundamental Research Funds for the Central Universities
文摘We conduct an electron magnetohydrodynamics magnetic reconnection experiment with guide-field in our Keda linear magnetized plasma device, in which two pulsed currents with the same direction are conducted in parallel with the axial direction of the main chamber of the device using two long aluminum sticks. After approximately 5μs, an X-type magnetic field line topology is formed at the center of the chamber. With the formation of the X-type topology of magnetic field lines, we can also find the rapid increase of the current and ratio of the common flux to the private flux in this area. Additionally, a reduction in the plasma density and the plasma density concentration along one pair of separatrices can also be found.
基金supported in part by the NNSF of China (11101144,11171377)Research Initiation Project for High-level Talents (201031) of North China University of Water Resources and Electric Power
文摘In this article, regularity criteria for the 3D magnetohydrodynamic equations are investigated. Some sufficient integrability conditions on two components or the gradient of two components of u ＋ B and u - B in Morrey-Campanato spaces are obtained.
基金Project Supported by the National Natural Science Foundation of China （Grant Nos 10375070 and 10305012）.Acknowledgement The authors would like to thank Professor Yi Liu of the South-Western Institute of Physics, Chengdu, China for valuable discussions.
文摘Multi-channel soft x-ray （SX） detectors are applied to generate images of magnetohydrodynamic （MHD） oscillation on the HT-7 tokamak, and the data from SX cameras are analysed by using the Fourier-Bessel harmonic reconstruction method and the singular value decomposition. The image reconstruction of SX emissivity is obtained on the assumption of plasma rigid rotation, One of the important phenomena in the HT-7 discharge is the transition from the sawtooth oscillations to the MHD oscillations when the plasma density grows higher. The MHD structure observed in the SX tomography is featured as follows： the magnetic surface of MHD structure is made up of the crescent-shaped ＂hot core＂ and the circular ＂cold bubble＂. The structure of the magnetic surface is relatively stable. It rotates in the direction of the electron diamagnetic drift at a frequency being the oscillation frequency of the MHD oscillations.
基金supported by NSFC(11371042)China 973 program(2011 CB808002)+2 种基金BSFC(1132006)CIT&TCD(20130312)the fund of the Beijing Education Committee(KZ 201210005005)
文摘The incompressible limit of the non-isentropic magnetohydrodynamic equations with zero thermal coefficient, in a two dimensional bounded domain with the Dirichlet condi- tion for velocity and perfectly conducting boundary condition for magnetic field, is rigorously justified.
文摘The present paper is concerned with a class of ex- act solutions to the steady Navier-Stokes equations for the incompressible Newtonian viscous electrically conducting fluid flow due to a porous disk rotating with a constant angu- lar speed. The three-dimensional hydromagnetic equations of motion are treated analytically to obtained exact solutions with the inclusion of suction and injection. The well-known thinning/thickening flow field effect of the suction/injection is better understood from the constructed closed form veloc- ity equations. Making use of this solution, analytical formu- las for the angular velocity components as well as for the permeable wall shear stresses are derived. Interaction of the resolved flow field with the surrounding temperature is fur- ther analyzed via the energy equation. The temperature field is shown to accord with the dissipation and the Joule heating. As a result, exact formulas are obtained for the temperature field which take different forms corresponding to the condi- tion of suction or injection imposed on the wall.
基金This work was supported by the KAUST Office of Spon-sored Research under Award No.URF/1/2162-01.
文摘The interaction between a converging cylindrical shock and double density interfaces in the presence of a saddle magnetic field is numerically investigated within the framework of ideal magnetohydrodynamics.Three fluids of differing densities are initially separated by the two perturbed cylindrical interfaces.The initial incident converging shock is generated from a Riemann problem upstream of the first interface.The effect of the magnetic field on the instabilities is studied through varying the field strength.It shows that the Richtmyer-Meshkov and Rayleigh-Taylor instabilities are mitigated by the field,however,the extent of the suppression varies on the interface which leads to non-axisymmetric growth of the perturbations.The degree of asymmetry of the interfacial growth rate is increased when the seed field strength is increased.
基金Project supported by the National Natural Science Foundation of China(Nos.11971410 and12071404)the Natural Science Foundation of Hunan Province of China(No.2019JJ40279)+2 种基金the Excellent Youth Program of Scientific Research Project of Hunan Provincial Department of Education(Nos.18B064 and 20B564)the China Postdoctoral Science Foundation(Nos.2018T110073 and 2018M631402)the International Scientific and Technological Innovation Cooperation Base of Hunan Province for Computational Science(No.2018WK4006)。
文摘Based on local algorithms,some parallel finite element(FE)iterative methods for stationary incompressible magnetohydrodynamics(MHD)are presented.These approaches are on account of two-grid skill include two major phases:find the FE solution by solving the nonlinear system on a globally coarse mesh to seize the low frequency component of the solution,and then locally solve linearized residual subproblems by one of three iterations(Stokes-type,Newton,and Oseen-type)on subdomains with fine grid in parallel to approximate the high frequency component.Optimal error estimates with regard to two mesh sizes and iterative steps of the proposed algorithms are given.Some numerical examples are implemented to verify the algorithm.
文摘This paper studies stratified magnetohydrodynamic （MHD） flow of tan- gent hyperbolic nanofluid past an inclined exponentially stretching surface. The flow is subjected to velocity, thermal, and solutal boundary conditions. The partial differential systems are reduced to ordinary differential systems using appropriate transformations. The reduced systems are solved for convergent series solutions. The velocity, temperature, and concentration fields are discussed for different physical parameters. The results indi- cate that the temperature and the thermal boundary layer thickness increase noticeably for large values of Brownian motion and thermophoresis effects. It is also observed that the buoyancy parameter strengthens the velocity field, showing a decreasing behavior of temperature and nanoparticle volume fraction profiles.
文摘To control the deflection of the gas plasma jet, a new analytical method is proposed based on the Magnetohydrodynamic(MHD) technique. Based on the typical MHD power generation model, the applied voltage is applied to the staggered electrodes, that is, a pair of electrodes on the same side wall are connected to generate an axial current in the channel. Under the action of the magnetic field perpendicular to the direction of the flow, the plasma is subjected to electromagnetic forces perpendicular to these two directions, and the jet is deflected. The computational model including the Navier-Stokes equations coupled with electromagnetic source terms, the electric potential equation and Ohm’s law is solved. The deflection of the gas jet under the action of an electromagnetic field is observed, and the maximum deflection angle is about 14.8°. The influences of the electric field, magnetic field, and conductivity on the jet deflection are studied. Results show that although the influences of these three factors on the deflection are similar, and the effect of increasing the electric field strength is slightly greater, priority should be given to increasing the magnetic field strength from the perspective of reducing energy consumption. The Stuart number is introduced to assess the ability of electromagnetic force to control jet deflection. When the electromagnetic parameters are constant, this solution provides better control of low-density and low-speed fluid flows. The calculation results show that using the staggered electrode method configuration is feasible in terms of controlling the deflection of a plasma jet deflection.
基金the financial support of National Board forHigher Mathematics (NBHM),DAE,Mumbai,India for pursuing this workThe research of A. Alsaedi is partially supported by the Deanship of Scientific Research (DSR),King Abdulaziz University,Jeddah,Saudi Arabia
文摘In this analysis,the magnetohydrodynamic boundary layer flow of Casson fluid over a permeable stretching/shrinking sheet in the presence of wall mass transfer is studied.Using similarity transformations,the governing equations are converted to an ordinary differential equation and then solved analytically.The introduction of a magnetic field changes the behavior of the entire flow dynamics in the shrinking sheet case and also has a major impact in the stretching sheet case.The similarity solution is always unique in the stretching case,and in the shrinking case the solution shows dual nature for certain values of the parameters.For stronger magnetic field,the similarity solution for the shrinking sheet case becomes unique.
基金supported by the National MCF Energy R&D Program of China(No.2018YFE0309100)National Natural Science Foundation of China(NSFC)(No.11905078)‘the Fundamental Research Funds for the Central Universities’(No.2020kfy XJJS003)。
文摘Magnetohydrodynamic(MHD)instabilities are widely observed during tokamak plasma operation.Magnetic diagnostics provide important information which supports the understanding and control of MHD instabilities.This paper presents the current status of the magnetic diagnostics dedicated to measuring MHD instabilities at the J-TEXT tokamak;the diagnostics consist of five Mirnov probe arrays for measuring high-frequency magnetic perturbations and two saddle-loop arrays for low-frequency magnetic perturbations,such as the locked mode.In recent years,several changes have been made to these arrays.The structure of the probes in the poloidal Mirnov arrays has been optimized to improve their mechanical strength,and the number of in-vessel saddle loops has also been improved to support better spatial resolution.Due to the installation of high-field-side(HFS)divertor targets in early 2019,some of the probes were removed,but an HFS Mirnov array was designed and installed behind the targets.Owing to its excellent toroidal symmetry,the HFS Mirnov array has,for the first time at J-TEXT,provided valuable new information about the locked mode and the quasi-static mode(QSM)in the HFS.Besides,various groups of magnetic diagnostics at different poloidal locations have been systematically used to measure the QSM,which confirmed the poloidal mode number m and the helical structure of the QSM.By including the HFS information,the 2/1 resonant magnetic perturbation(RMP)-induced locked mode was measured to have a poloidal mode number m of~2.
