Let(u,B)be a strong solution of the magneto-hydrodynamic system on three dimensional torus T^(3).In this note,using the properties of the curl operator,we show that‖(▽×(u-B),▽×(u+B))(·,t)‖L^(1)+1/2v...Let(u,B)be a strong solution of the magneto-hydrodynamic system on three dimensional torus T^(3).In this note,using the properties of the curl operator,we show that‖(▽×(u-B),▽×(u+B))(·,t)‖L^(1)+1/2v‖(u-B,u+B)(·,t)‖_(L^(2))^(2)is decreasing in time t as long as the solution(u,B)(·,t)exists,where∇×w means the curl of the vector function w,and v>0 is the viscosity coefficient.展开更多
The present exploration is conducted to describe the motion of viscous fluid embedded in squeezed channel under the applied magnetics effects.The processes of heat and mass transport incorporate the temperature-depend...The present exploration is conducted to describe the motion of viscous fluid embedded in squeezed channel under the applied magnetics effects.The processes of heat and mass transport incorporate the temperature-dependent binary chemical reaction with modified Arrhenius theory of activation energy function which is not yet disclosed for squeezing flow mechanism.The flow,heat and mass regime are exposed to be governed via dimensionless,highly non-linear,ordinary differential equations (ODEs) under no-slip walls boundary conditions.A well-tempered analytical convergent procedure is adopted for the solutions of boundary value problem.A detailed study is accounted through graphs in the form of flow velocity field,temperature and fluid concentration distributions for various emerging parameters of enormous interest.Skin-friction,Nusselt and Sherwood numbers have been acquired and disclosed through plots.The results indicate that fluid temperature follows an increasing trend with dominant dimensionless reaction rate σ and activation energy parameter E.However,an increment in σ and E parameters is found to decline in fluid concentration.The current study arises numerous engineering and industrial processes including polymer industry,compression and injection shaping,lubrication system,formation of paper sheets,thin fiber,molding of plastic sheets.In the area of chemical engineering,geothermal engineering,cooling of nuclear reacting,nuclear or chemical system,bimolecular reactions,biochemical process and electrically conducting polymeric flows can be controlled by utilizing magnetic fields.Motivated by such applications,the proposed study has been developed.展开更多
This article proves the logarithmically improved Serrin＇s criterion for solutions of the 3D generalized magneto-hydrodynamic equations in terms of the gradient of the velocity field, which can be regarded as improvem...This article proves the logarithmically improved Serrin＇s criterion for solutions of the 3D generalized magneto-hydrodynamic equations in terms of the gradient of the velocity field, which can be regarded as improvement of results in [10] （Luo Y W. On the regularity of generalized MHD equations. J Math Anal Appl, 2010, 365： 806-808） and [18] （Zhang Z J. Remarks on the regularity criteria for generalized MHD equations. J Math Anal Appl, 2011, 375：799 802）.展开更多
This paper concerns the Cauchy problem of the 3D generalized incompressible magneto-hydrodynamic(GMHD) equations. By using the Fourier localization argument and the Littlewood-Paley theory, we get local well-posedness...This paper concerns the Cauchy problem of the 3D generalized incompressible magneto-hydrodynamic(GMHD) equations. By using the Fourier localization argument and the Littlewood-Paley theory, we get local well-posedness results of the GMHD equations with large initial data(u0, b0) belonging to the critical Fourier-Besov-Morrey spaces FN^1-2α+3/p'+λ/pp,λ,q(R^3) Moreover, stability of global solutions is also discussed.展开更多
This paper introduces the notion of Tokamak Magneto-Hydrodynamics （TMHD）, which explicitly reflects the anisotropy of a high temperature tokamak plasma. The set of TMHD equations is formulated for simulation of macr...This paper introduces the notion of Tokamak Magneto-Hydrodynamics （TMHD）, which explicitly reflects the anisotropy of a high temperature tokamak plasma. The set of TMHD equations is formulated for simulation of macroscopic plasma dynamics and disruptions in tokamaks. Free from the Courant restriction on the time step, this set of equations is adequate to plasma dynamics with realistic parameters of high performance plasmas and does not require any extension of the MHD plasma model. At the same time, TMHD requires the use of magnetic field aligned numerical grids. Examples of their use in 2-dimensional cases of tokamak equilibria and dynamics of the wall touching kink mode are presented. For the 3-dimensional case of an ergodic magnetic field, this paper introduces the reference magnetic coordinates as a practical algorithm for generating adaptive grids for TMHD.展开更多
The approximate solution of the magneto-hydrodynamic （MHD） boundary layer flow over a nonlinear stretching sheet is obtained by combining the Lie symmetry method with the homotopy perturbation method. The approximat...The approximate solution of the magneto-hydrodynamic （MHD） boundary layer flow over a nonlinear stretching sheet is obtained by combining the Lie symmetry method with the homotopy perturbation method. The approximate solution is tabulated, plotted for the values of various parameters and compared with the known solutions. It is found that the approximate solution agrees very well with the known numerical solutions, showing the reliability and validity of the present work.展开更多
Natural convection flow in enclosure has different applications such as room ventilation, heat exchangers, the cooling system of a building etc. The Finite-Element method based on the Galerkin weighted residual approa...Natural convection flow in enclosure has different applications such as room ventilation, heat exchangers, the cooling system of a building etc. The Finite-Element method based on the Galerkin weighted residual approach is used to solve two-dimensional governing mass, momentum and energy-equations for natural convection flow in the presence of a magnetic field on a roof top with semi-circular heater. In the enclosure the horizontal lower wall was heated, the vertical two walls were adiabatic, inside the semi-circular heater, the wavy top wall cooled. The parameters Rayleigh number, Hartmann number and Prandtl number are considered. The effects of the Hartmann number and Rayleigh number on the streamlines, isotherms, velocity profiles and average Nusselt number are examined graphically. The local Nusselt number and the average Nusselt number of the heated portion of the enclosure with the semi-circular heater are presented in this paper. Finally, for the validation of the existing work, the current results are compared with published results and the auspicious agreement is achieved.展开更多
We present in this paper several efficient numerical schemes for the magneto-hydrodynamic(MHD)equations. These semi-discretized(in time) schemes are based on the standard and rotational pressure-correction schemes for...We present in this paper several efficient numerical schemes for the magneto-hydrodynamic(MHD)equations. These semi-discretized(in time) schemes are based on the standard and rotational pressure-correction schemes for the Navier-Stokes equations and do not involve a projection step for the magnetic field. We show that these schemes are unconditionally energy stable, present an effective algorithm for their fully discrete versions and carry out demonstrative numerical experiments.展开更多
Consider d-dimensional magneto-hydrodynamic(MHD)equations with fractional dissipations driven by multiplicative noise.First,we prove the existence of martingale solutions for stochastic fractional MHD equations in the...Consider d-dimensional magneto-hydrodynamic(MHD)equations with fractional dissipations driven by multiplicative noise.First,we prove the existence of martingale solutions for stochastic fractional MHD equations in the case of d=2,3 andα∧β〉0,whereα,βare the parameters of the fractional dissipations in the equation.Second,for d=2,3 andα∧β≥12+d4,we show the pathwise uniqueness of solutions and then obtain the existence and uniqueness of strong solutions using the Yamada-Watanabe theorem.Furthermore,we establish the exponential mixing property for stochastic MHD equations with degenerate multiplicative noise when d=2,3 andα∧β≥12+d4.展开更多
We investigate the Cauchy problem for the 3D magneto-hydrodynamics equations with only horizontal dissipation for the small initial data. With the help of the dissipation in the horizontal direction and the structure ...We investigate the Cauchy problem for the 3D magneto-hydrodynamics equations with only horizontal dissipation for the small initial data. With the help of the dissipation in the horizontal direction and the structure of the system, we analyze the properties of the decay of the solution and apply these decay properties to get the global regularity of the solution. In the process, we mainly use the frequency decomposition in Green's function method and energy method.展开更多
This work investigates thermal enhancement in fluid flow over a nonlinear stretching sheet.The thickness of the sheet is variable and the flow of the fluid is affected by solar radiation energy with Thompson and Troia...This work investigates thermal enhancement in fluid flow over a nonlinear stretching sheet.The thickness of the sheet is variable and the flow of the fluid is affected by solar radiation energy with Thompson and Troian slip effects.The flow is magnetized by applying a magnetic field in the normal direction to the flow system.Moreover,thermal transport is controlled by incorporating the Cattaneo-Christov heat fluid model into the flow problem.The governing equations,initially framed in their dimensional form,are meticulously transformed into a dimensionless framework to simplify the analysis.These dimensionless equations are then solved using the homotopy analysis method(HAM).It is observed in this study that upsurges in the stagnation parameter,critical shear rate and velocity slip factor augment the velocity distribution while reducing the thermal profiles.The velocity distribution deteriorates while the thermal profiles are amplified with expansions in the magnetic factor and power law index.The thermal distribution also increases with rising Prandtl number and radiation factor.Augmentation of the power-law index,velocity slip parameter,critical shear rate,magnetic factor and stagnation parameter leads to an increased Nusselt number.The modeled problem is validated by comparing the current results with established work for different values of nonlinear stretching factor n in terms of the drag force and thermal flow rate at η=0,and a good agreement is observed between the current and established results.展开更多
This paper presents an integrated research scheme for vector deflection and energy extraction in a gas plasma jet under Magneto-Hydrodynamic(MHD)control.A MHDcontrolled thrust-vector test rig was used to conduct the e...This paper presents an integrated research scheme for vector deflection and energy extraction in a gas plasma jet under Magneto-Hydrodynamic(MHD)control.A MHDcontrolled thrust-vector test rig was used to conduct the experimental research.A gas plasma was obtained by injecting ionization seeds of Cs2CO3 into the combustion chamber via artificially forced ionization.The effects of the gas temperature and ionization seed mass fraction on the plasma jet deflection and energy extraction were experimentally verified under an applied magnetic field.The experimental results were analyzed theoretically.The results showed that the deflection amplitude of the gas plasma jet and the extracted voltage signal intensity increased with increasing gas temperature and the ionization seed mass fraction.The extracted dynamic voltage signals proved that the ionization seeds of Cs2CO3 induced gas ionization at 1173 K.The experiment verified that it is feasible to simultaneously achieve jet deflection and extract energy under the action of an external magnetic field.展开更多
In this article, we present accurate analytical solutions for boundary layer flow and heat transfer of an incompressible and electrically conducting viscoelastic fluid over a linearly stretching surface subject to a t...In this article, we present accurate analytical solutions for boundary layer flow and heat transfer of an incompressible and electrically conducting viscoelastic fluid over a linearly stretching surface subject to a transverse uniform magnetic field using the homotopy analysis method （HAM） for two general types of non-isothermal boundary conditions. In addition, we demonstrate that the previously reported analytical solutions for the temperature field given in terms of Kummer＇s function do not converge at the boundary. We provide a graphical and numerical demonstration of the convergence of the HAM solutions and tabulate the effects of various parameters on the skin friction coefficient and wall heat transfer.展开更多
The vibrating electrode method was proposed in the electro-slag remelting （ESR） process in this paper, and the effect of vibrating electrode on the solidification structure of ingot was studied. A transient three- d...The vibrating electrode method was proposed in the electro-slag remelting （ESR） process in this paper, and the effect of vibrating electrode on the solidification structure of ingot was studied. A transient three- dimensional （3D） coupled mathematical model was established to simulate the electromagnetic phenomenon, fluid flow as well as pool shape in the ESIR process with the vibrating electrode. The finite element volume method is developed to solve the electromagnetic field using ANSYS mechanical APDL software. Moreover, the electromagnetic force and Joule heating are interpolated as the source term of the momentum and energy equations. The multi-physical fields have been investigated and compared between the traditional electrode and the vibrating electrode in the ESR process. The results show that the drop process of metal droplets with the traditional electrode is scattered randomly. However, the drop process of metal droplets with the vibrating electrode is periodic. The highest temperature of slag layer with the vibrating electrode is higher than that with the traditional electrode, which can increase the melting rate due to the enhanced heat transfer in the vicinity of the electrode tip. The results also show that when the amplitude and frequency of the vibrating electrode increase, the cycle of drop process of metal droplets decreases significantly.展开更多
Project New Orion entails a pulsed nuclear space propulsion system that utilizes photofission through the implementation of an ultra-intense laser. The historical origins derive from the endeavors of Project Orion, wh...Project New Orion entails a pulsed nuclear space propulsion system that utilizes photofission through the implementation of an ultra-intense laser. The historical origins derive from the endeavors of Project Orion, which utilized thermonuclear devices to impart a considerable velocity increment on the respective spacecraft. The shear magnitude of Project Orion significantly detracts from the likelihood of progressive research development testing and evaluation. Project New Orion incorporates a more feasible pathway for the progressive research development testing and evaluation of the pulsed nuclear space propulsion system. Photofission through the application of an ultra-intense laser enables a much more controllable and scalable nuclear yield. The energy source for the ultra-intense laser is derived from a first stage liquid hydrogen and liquid oxygen chemical propulsion system. A portion of the thermal/kinetic energy of the rocket propulsive fluid is converted to electrical energy through a magneto-hydrodynamic generator with cryogenic propellant densification for facilitating the integral superconducting magnets. Fundamental analysis of Project New Orion demonstrates the capacity to impart a meaningful velocity increment through ultra-intense laser derived photofission on a small spacecraft.展开更多
Gas spark gap is widely used in any pulsed power system as the key element which directly determines its repetitive performance and output characteristics. Among many factors of threeelectrode gas spark gap, backgroun...Gas spark gap is widely used in any pulsed power system as the key element which directly determines its repetitive performance and output characteristics. Among many factors of threeelectrode gas spark gap, background pressure is of much importance in determining the gap performance parameters such as the delay and jitter, and relevant studies have been rarely performed. A magneto-hydrodynamic model of the arc in gas spark gap is built and the effects of background pressure on the arc characteristics are discussed in this paper. It is demonstrated that a higher background pressure may result in radial compression of the arc column, a higher arc voltage, and a lower declination rate of arc resistance in the first quarter cycle. Relevant simulation data would be helpful for the optimization of the design of gas spark gap.展开更多
In this work,several key scaling laws of the quasi-static magnetic compression of field reversed configuration(FRC)plasma(Spencer et al 1983 Phys.Fluids 261564)are amended from a series of two-dimensional FRC MHD equi...In this work,several key scaling laws of the quasi-static magnetic compression of field reversed configuration(FRC)plasma(Spencer et al 1983 Phys.Fluids 261564)are amended from a series of two-dimensional FRC MHD equilibriums numerically obtained using the Grad–Shafranov equation solver NIMEQ.Based on the new scaling for the elongation and the magnetic fields at the separatrix and the wall,the empirically stable limits for the compression ratio,the fusion gain,and the neutron yield are evaluated,which may serve as a more accurate estimate for the upper ceiling of performance from the magnetic compression of FRC plasma as a potential fusion energy as well as neutron source devices.展开更多
In this contemporary study,theoritical investigation of nanofluidic model is thought-out.Two-dimensional nanomaterials based mixed flow is considered here.Convective solar radiative heat transport properties have been...In this contemporary study,theoritical investigation of nanofluidic model is thought-out.Two-dimensional nanomaterials based mixed flow is considered here.Convective solar radiative heat transport properties have been investigated over a nonlinearly stretched wall in the presence of magneto-hydrodynamic(MHD),by innovative application of semi analytical“optimal homotopy asymptotic method(OHAM)”.OHAM does not require any discretization,linearization and small parameter assumption.OHAM describes extremely precise 1^(st)/2^(nd) order solutions without the need of computing further higher order terms,therefore,fast convergence is observed.Nanofluidic governing model is transformed into system of ordinary differential equations(ODEs)by exploitation of similarity transformation.To study the significance of radiation parameter alongwith thermophoresis parameter,a semi analytical solver is applied to the transformed system.In this work,Brownianmotion,influence ofmagnetic field,Lewis number,Prandtl number,Eckert number and Biot number have investigated on velocity,temperature and nanoparticle concentration profiles.The study provides sufficient number of graphical representations to demonstrate the inspiration of mentioned parameters.展开更多
The stability(or instability)of finite sized magnetic island could play a significant role in disruption avoidance or disruption mitigation dynamics.Especially,various current and pressure profile modifications,such a...The stability(or instability)of finite sized magnetic island could play a significant role in disruption avoidance or disruption mitigation dynamics.Especially,various current and pressure profile modifications,such as the current drive and heating caused by electron cyclotron wave,or the radiative cooling and current expulsion caused by the shattered pellet injection could be applied within the island to modify its stability,thus changing the ensuing dynamics.In this study,we calculate the mode structure modification caused by such profile changes within the island using the perturbed equilibrium approach,thus obtain the change of stability criterion Δ′ and assess the corresponding quasi-linear island stability.The positive helical current perturbation is found to always stabilize the island,while the negative one is found to do the opposite,in agreement with previous results.The pressure bump or hole within the island has a more complicated stability impact.In the small island regime,its contribution is monotonic,with pressure bump that tends to stabilize the island while pressure hole destabilizes it.This effect is relatively weak,though,due to the cancellation of the pressure term’s odd parity contribution in the second derivatives of the mode structure.In the large island regime,such cancellation is broken due to the island asymmetry,and the pressure contribution to stability is manifested,which is non-monotonic.The stability analysis in this paper helps to more accurately clarify the expected island response in the presence of profile modifications caused by disruption avoidance or mitigation systems.展开更多
基金supported by the National Natural Science Foundation of China(12371123).
文摘Let(u,B)be a strong solution of the magneto-hydrodynamic system on three dimensional torus T^(3).In this note,using the properties of the curl operator,we show that‖(▽×(u-B),▽×(u+B))(·,t)‖L^(1)+1/2v‖(u-B,u+B)(·,t)‖_(L^(2))^(2)is decreasing in time t as long as the solution(u,B)(·,t)exists,where∇×w means the curl of the vector function w,and v>0 is the viscosity coefficient.
文摘The present exploration is conducted to describe the motion of viscous fluid embedded in squeezed channel under the applied magnetics effects.The processes of heat and mass transport incorporate the temperature-dependent binary chemical reaction with modified Arrhenius theory of activation energy function which is not yet disclosed for squeezing flow mechanism.The flow,heat and mass regime are exposed to be governed via dimensionless,highly non-linear,ordinary differential equations (ODEs) under no-slip walls boundary conditions.A well-tempered analytical convergent procedure is adopted for the solutions of boundary value problem.A detailed study is accounted through graphs in the form of flow velocity field,temperature and fluid concentration distributions for various emerging parameters of enormous interest.Skin-friction,Nusselt and Sherwood numbers have been acquired and disclosed through plots.The results indicate that fluid temperature follows an increasing trend with dominant dimensionless reaction rate σ and activation energy parameter E.However,an increment in σ and E parameters is found to decline in fluid concentration.The current study arises numerous engineering and industrial processes including polymer industry,compression and injection shaping,lubrication system,formation of paper sheets,thin fiber,molding of plastic sheets.In the area of chemical engineering,geothermal engineering,cooling of nuclear reacting,nuclear or chemical system,bimolecular reactions,biochemical process and electrically conducting polymeric flows can be controlled by utilizing magnetic fields.Motivated by such applications,the proposed study has been developed.
文摘This article proves the logarithmically improved Serrin＇s criterion for solutions of the 3D generalized magneto-hydrodynamic equations in terms of the gradient of the velocity field, which can be regarded as improvement of results in [10] （Luo Y W. On the regularity of generalized MHD equations. J Math Anal Appl, 2010, 365： 806-808） and [18] （Zhang Z J. Remarks on the regularity criteria for generalized MHD equations. J Math Anal Appl, 2011, 375：799 802）.
文摘This paper concerns the Cauchy problem of the 3D generalized incompressible magneto-hydrodynamic(GMHD) equations. By using the Fourier localization argument and the Littlewood-Paley theory, we get local well-posedness results of the GMHD equations with large initial data(u0, b0) belonging to the critical Fourier-Besov-Morrey spaces FN^1-2α+3/p'+λ/pp,λ,q(R^3) Moreover, stability of global solutions is also discussed.
基金supported by US DoE Contract No.DE-AC02-09-CH11466by the National Magnetic Confinement Fusion Science Program of China(No.2011GB105003)by the US DOE SBIR grant#94307S10-Ⅱ
文摘This paper introduces the notion of Tokamak Magneto-Hydrodynamics （TMHD）, which explicitly reflects the anisotropy of a high temperature tokamak plasma. The set of TMHD equations is formulated for simulation of macroscopic plasma dynamics and disruptions in tokamaks. Free from the Courant restriction on the time step, this set of equations is adequate to plasma dynamics with realistic parameters of high performance plasmas and does not require any extension of the MHD plasma model. At the same time, TMHD requires the use of magnetic field aligned numerical grids. Examples of their use in 2-dimensional cases of tokamak equilibria and dynamics of the wall touching kink mode are presented. For the 3-dimensional case of an ergodic magnetic field, this paper introduces the reference magnetic coordinates as a practical algorithm for generating adaptive grids for TMHD.
基金Project supported by the National Natural Science Foundation of China （Grant No. 11071159） and the College Science Research Project of Inner Mongolia, China （Grant No. NJzy08180）.
文摘The approximate solution of the magneto-hydrodynamic （MHD） boundary layer flow over a nonlinear stretching sheet is obtained by combining the Lie symmetry method with the homotopy perturbation method. The approximate solution is tabulated, plotted for the values of various parameters and compared with the known solutions. It is found that the approximate solution agrees very well with the known numerical solutions, showing the reliability and validity of the present work.
文摘Natural convection flow in enclosure has different applications such as room ventilation, heat exchangers, the cooling system of a building etc. The Finite-Element method based on the Galerkin weighted residual approach is used to solve two-dimensional governing mass, momentum and energy-equations for natural convection flow in the presence of a magnetic field on a roof top with semi-circular heater. In the enclosure the horizontal lower wall was heated, the vertical two walls were adiabatic, inside the semi-circular heater, the wavy top wall cooled. The parameters Rayleigh number, Hartmann number and Prandtl number are considered. The effects of the Hartmann number and Rayleigh number on the streamlines, isotherms, velocity profiles and average Nusselt number are examined graphically. The local Nusselt number and the average Nusselt number of the heated portion of the enclosure with the semi-circular heater are presented in this paper. Finally, for the validation of the existing work, the current results are compared with published results and the auspicious agreement is achieved.
基金supported by National Science Foundation of USA (Grant No. DMS1419053)
文摘We present in this paper several efficient numerical schemes for the magneto-hydrodynamic(MHD)equations. These semi-discretized(in time) schemes are based on the standard and rotational pressure-correction schemes for the Navier-Stokes equations and do not involve a projection step for the magnetic field. We show that these schemes are unconditionally energy stable, present an effective algorithm for their fully discrete versions and carry out demonstrative numerical experiments.
基金The research of S.Li was supported by the National Natural Science Foundation of China(Grant No.12001247)the Natural Science Foundation of Jiangsu Province(No.BK20201019)+2 种基金the Natural Science Foundation of Jiangsu Higher Education Institutions of China(No.20KJB110015)the Foundation of Jiangsu Normal University(No.19XSRX023)The research of W.Liu was supported by the National Natural Science Foundation of China(Grant Nos.11822106,11831014,12090011)and the PAPD of Jiangsu Higher Education Institutions.
文摘Consider d-dimensional magneto-hydrodynamic(MHD)equations with fractional dissipations driven by multiplicative noise.First,we prove the existence of martingale solutions for stochastic fractional MHD equations in the case of d=2,3 andα∧β〉0,whereα,βare the parameters of the fractional dissipations in the equation.Second,for d=2,3 andα∧β≥12+d4,we show the pathwise uniqueness of solutions and then obtain the existence and uniqueness of strong solutions using the Yamada-Watanabe theorem.Furthermore,we establish the exponential mixing property for stochastic MHD equations with degenerate multiplicative noise when d=2,3 andα∧β≥12+d4.
基金National Natural Science Foundation of China (Grant No. 11771284).
文摘We investigate the Cauchy problem for the 3D magneto-hydrodynamics equations with only horizontal dissipation for the small initial data. With the help of the dissipation in the horizontal direction and the structure of the system, we analyze the properties of the decay of the solution and apply these decay properties to get the global regularity of the solution. In the process, we mainly use the frequency decomposition in Green's function method and energy method.
基金supported via funding from Prince Sattam bin Abdulaziz University project number(PSAU/2025/R/1446)。
文摘This work investigates thermal enhancement in fluid flow over a nonlinear stretching sheet.The thickness of the sheet is variable and the flow of the fluid is affected by solar radiation energy with Thompson and Troian slip effects.The flow is magnetized by applying a magnetic field in the normal direction to the flow system.Moreover,thermal transport is controlled by incorporating the Cattaneo-Christov heat fluid model into the flow problem.The governing equations,initially framed in their dimensional form,are meticulously transformed into a dimensionless framework to simplify the analysis.These dimensionless equations are then solved using the homotopy analysis method(HAM).It is observed in this study that upsurges in the stagnation parameter,critical shear rate and velocity slip factor augment the velocity distribution while reducing the thermal profiles.The velocity distribution deteriorates while the thermal profiles are amplified with expansions in the magnetic factor and power law index.The thermal distribution also increases with rising Prandtl number and radiation factor.Augmentation of the power-law index,velocity slip parameter,critical shear rate,magnetic factor and stagnation parameter leads to an increased Nusselt number.The modeled problem is validated by comparing the current results with established work for different values of nonlinear stretching factor n in terms of the drag force and thermal flow rate at η=0,and a good agreement is observed between the current and established results.
基金supported by the National Natural Science Foundation of China(No.90716025)。
文摘This paper presents an integrated research scheme for vector deflection and energy extraction in a gas plasma jet under Magneto-Hydrodynamic(MHD)control.A MHDcontrolled thrust-vector test rig was used to conduct the experimental research.A gas plasma was obtained by injecting ionization seeds of Cs2CO3 into the combustion chamber via artificially forced ionization.The effects of the gas temperature and ionization seed mass fraction on the plasma jet deflection and energy extraction were experimentally verified under an applied magnetic field.The experimental results were analyzed theoretically.The results showed that the deflection amplitude of the gas plasma jet and the extracted voltage signal intensity increased with increasing gas temperature and the ionization seed mass fraction.The extracted dynamic voltage signals proved that the ionization seeds of Cs2CO3 induced gas ionization at 1173 K.The experiment verified that it is feasible to simultaneously achieve jet deflection and extract energy under the action of an external magnetic field.
文摘In this article, we present accurate analytical solutions for boundary layer flow and heat transfer of an incompressible and electrically conducting viscoelastic fluid over a linearly stretching surface subject to a transverse uniform magnetic field using the homotopy analysis method （HAM） for two general types of non-isothermal boundary conditions. In addition, we demonstrate that the previously reported analytical solutions for the temperature field given in terms of Kummer＇s function do not converge at the boundary. We provide a graphical and numerical demonstration of the convergence of the HAM solutions and tabulate the effects of various parameters on the skin friction coefficient and wall heat transfer.
基金financially supported by the National Natural Science Foundation of China(No.51275320)
文摘The vibrating electrode method was proposed in the electro-slag remelting （ESR） process in this paper, and the effect of vibrating electrode on the solidification structure of ingot was studied. A transient three- dimensional （3D） coupled mathematical model was established to simulate the electromagnetic phenomenon, fluid flow as well as pool shape in the ESIR process with the vibrating electrode. The finite element volume method is developed to solve the electromagnetic field using ANSYS mechanical APDL software. Moreover, the electromagnetic force and Joule heating are interpolated as the source term of the momentum and energy equations. The multi-physical fields have been investigated and compared between the traditional electrode and the vibrating electrode in the ESR process. The results show that the drop process of metal droplets with the traditional electrode is scattered randomly. However, the drop process of metal droplets with the vibrating electrode is periodic. The highest temperature of slag layer with the vibrating electrode is higher than that with the traditional electrode, which can increase the melting rate due to the enhanced heat transfer in the vicinity of the electrode tip. The results also show that when the amplitude and frequency of the vibrating electrode increase, the cycle of drop process of metal droplets decreases significantly.
文摘Project New Orion entails a pulsed nuclear space propulsion system that utilizes photofission through the implementation of an ultra-intense laser. The historical origins derive from the endeavors of Project Orion, which utilized thermonuclear devices to impart a considerable velocity increment on the respective spacecraft. The shear magnitude of Project Orion significantly detracts from the likelihood of progressive research development testing and evaluation. Project New Orion incorporates a more feasible pathway for the progressive research development testing and evaluation of the pulsed nuclear space propulsion system. Photofission through the application of an ultra-intense laser enables a much more controllable and scalable nuclear yield. The energy source for the ultra-intense laser is derived from a first stage liquid hydrogen and liquid oxygen chemical propulsion system. A portion of the thermal/kinetic energy of the rocket propulsive fluid is converted to electrical energy through a magneto-hydrodynamic generator with cryogenic propellant densification for facilitating the integral superconducting magnets. Fundamental analysis of Project New Orion demonstrates the capacity to impart a meaningful velocity increment through ultra-intense laser derived photofission on a small spacecraft.
基金supported by National Natural Science Foundation of China (No. 51807184)
文摘Gas spark gap is widely used in any pulsed power system as the key element which directly determines its repetitive performance and output characteristics. Among many factors of threeelectrode gas spark gap, background pressure is of much importance in determining the gap performance parameters such as the delay and jitter, and relevant studies have been rarely performed. A magneto-hydrodynamic model of the arc in gas spark gap is built and the effects of background pressure on the arc characteristics are discussed in this paper. It is demonstrated that a higher background pressure may result in radial compression of the arc column, a higher arc voltage, and a lower declination rate of arc resistance in the first quarter cycle. Relevant simulation data would be helpful for the optimization of the design of gas spark gap.
基金supported by the National Magnetic Confinement Fusion Program of China (No. 2017YFE0301805)National Natural Science Foundation of China (No. 51821005)+3 种基金the Fundamental Research Funds for the Central Universities at Huazhong University of Science and Technology (No. 2019kfy XJJS193)the U.S. Department of Energy (Nos. DE-FG02-86ER53218 and DE-SC0018001)the supports from the NIMROD teamthe support from the Chinese Government Scholarship.
文摘In this work,several key scaling laws of the quasi-static magnetic compression of field reversed configuration(FRC)plasma(Spencer et al 1983 Phys.Fluids 261564)are amended from a series of two-dimensional FRC MHD equilibriums numerically obtained using the Grad–Shafranov equation solver NIMEQ.Based on the new scaling for the elongation and the magnetic fields at the separatrix and the wall,the empirically stable limits for the compression ratio,the fusion gain,and the neutron yield are evaluated,which may serve as a more accurate estimate for the upper ceiling of performance from the magnetic compression of FRC plasma as a potential fusion energy as well as neutron source devices.
文摘In this contemporary study,theoritical investigation of nanofluidic model is thought-out.Two-dimensional nanomaterials based mixed flow is considered here.Convective solar radiative heat transport properties have been investigated over a nonlinearly stretched wall in the presence of magneto-hydrodynamic(MHD),by innovative application of semi analytical“optimal homotopy asymptotic method(OHAM)”.OHAM does not require any discretization,linearization and small parameter assumption.OHAM describes extremely precise 1^(st)/2^(nd) order solutions without the need of computing further higher order terms,therefore,fast convergence is observed.Nanofluidic governing model is transformed into system of ordinary differential equations(ODEs)by exploitation of similarity transformation.To study the significance of radiation parameter alongwith thermophoresis parameter,a semi analytical solver is applied to the transformed system.In this work,Brownianmotion,influence ofmagnetic field,Lewis number,Prandtl number,Eckert number and Biot number have investigated on velocity,temperature and nanoparticle concentration profiles.The study provides sufficient number of graphical representations to demonstrate the inspiration of mentioned parameters.
基金Project supported by the National MCF Energy Research and Development Program of China (Grant No. 2019YFE03010001)the National Natural Science Foundation of China (Grant No. 11905004)
文摘The stability(or instability)of finite sized magnetic island could play a significant role in disruption avoidance or disruption mitigation dynamics.Especially,various current and pressure profile modifications,such as the current drive and heating caused by electron cyclotron wave,or the radiative cooling and current expulsion caused by the shattered pellet injection could be applied within the island to modify its stability,thus changing the ensuing dynamics.In this study,we calculate the mode structure modification caused by such profile changes within the island using the perturbed equilibrium approach,thus obtain the change of stability criterion Δ′ and assess the corresponding quasi-linear island stability.The positive helical current perturbation is found to always stabilize the island,while the negative one is found to do the opposite,in agreement with previous results.The pressure bump or hole within the island has a more complicated stability impact.In the small island regime,its contribution is monotonic,with pressure bump that tends to stabilize the island while pressure hole destabilizes it.This effect is relatively weak,though,due to the cancellation of the pressure term’s odd parity contribution in the second derivatives of the mode structure.In the large island regime,such cancellation is broken due to the island asymmetry,and the pressure contribution to stability is manifested,which is non-monotonic.The stability analysis in this paper helps to more accurately clarify the expected island response in the presence of profile modifications caused by disruption avoidance or mitigation systems.
