We consider a relativistic two-fluid model of superfluidity,in which the superfluid is described by an order parameter that is a complex scalar field satisfying the nonlinear Klein-Gordon equation(NLKG).The coupling t...We consider a relativistic two-fluid model of superfluidity,in which the superfluid is described by an order parameter that is a complex scalar field satisfying the nonlinear Klein-Gordon equation(NLKG).The coupling to the normal fluid is introduced via a covariant current-current interaction,which results in the addition of an effective potential,whose imaginary part describes particle transfer between superfluid and normal fluid.Quantized vorticity arises in a class of singular solutions and the related vortex dynamics is incorporated in the modified NLKG,facilitating numerical analysis which is usually very complicated in the phenomenology of vortex filaments.The dual transformation to a string theory description(Kalb-Ramond)of quantum vorticity,the Magnus force,and the mutual friction between quantized vortices and normal fluid are also studied.展开更多
In this paper,we consider a model of compressible isentropic two-fluid magneto-hydrodynamics without resistivity in a strip domain in three dimensional space.By exploiting the two-tier energy method developed in[Anal ...In this paper,we consider a model of compressible isentropic two-fluid magneto-hydrodynamics without resistivity in a strip domain in three dimensional space.By exploiting the two-tier energy method developed in[Anal PDE,2013,6:1429–1533],we prove the global well-posedness of the governing model around a uniform magnetic field which is non-parallel to the horizontal boundary.Moreover,we show that the solution converges to the steady state at an almost exponential rate as time goes to infinity.Compared to the work of Tan and Wang[SIAM J Math Anal,2018,50:1432–1470],we need to overcome the difficulties caused by particles.展开更多
Optical superconducting transition-edge sensor(TES)has been widely used in quantum information,biological imaging,and fluorescence microscopy owing to its high quantum efficiency,low dark count,and photon number resol...Optical superconducting transition-edge sensor(TES)has been widely used in quantum information,biological imaging,and fluorescence microscopy owing to its high quantum efficiency,low dark count,and photon number resolving capability.The temperature sensitivity(α_(I))and current sensitivity(β_(I))are important parameters for optical TESs,which are generally extracted from the complex impedance.Here we present a method to extractα_(I)andβ_(I)based on a two-fluid model and compare the calculated current-voltage curves,pulse response,and theoretical energy resolution with the measured ones.This method shows qualitative agreement that is suitable for further optimization of optical TESs.展开更多
The Quintom dark energy is a proposal that explains the recent observations that mildly favor the equation of state of dark energy ω crossing -1 near the past. The Quintom model is often constructed by two scalar fie...The Quintom dark energy is a proposal that explains the recent observations that mildly favor the equation of state of dark energy ω crossing -1 near the past. The Quintom model is often constructed by two scalar fields, where one is the quintessence feld and another is the phantom field. The cosmological implication of the coupling of the two fields of the dark energy is out of question worth investigating. However, the consideration of the coupling in the field scenario is somewhat complex thus we propose an interacting two-fluid Quintom scenario for simplicity. The interaction between the two components is parametrized by a constant 71 in this scenario. The cosmological implications of this parametrization are investigated in detail in this paper. Also, a diagnostic for this model is performed by using the statefinder pairs {s, r} and {q, r}.展开更多
RH vacuum degasser is a very important secondary refining device in the production of high quality steels. The flow field of molten steel in RH system plays a significant role in determining productivity of the equipm...RH vacuum degasser is a very important secondary refining device in the production of high quality steels. The flow field of molten steel in RH system plays a significant role in determining productivity of the equipment. The homogeneous model and VOF method were often used to predict the flow field in RH system, but these kinds of models simplified the interaction between gas bubbles and molten steel. In the present work, a numerical model of a whole RH system, including vacuum degasser, immersed legs and ladle,was built based on gas-liquid two-fluid model, and it could be used to analyze the interaction between argon bubbles and molten steel, to understand the effect of the bubble size to the flow field.展开更多
The weakly ionized plasma flows in aerospace are commonly simulated by the single-fluid model,which cannot describe certain nonequilibrium phenomena by finite collisions of particles,decreasing the fidelity of the sol...The weakly ionized plasma flows in aerospace are commonly simulated by the single-fluid model,which cannot describe certain nonequilibrium phenomena by finite collisions of particles,decreasing the fidelity of the solution.Based on an alternative formulation of the targeted essentially non-oscillatory(TENO)scheme,a novel high-order numerical scheme is proposed to simulate the two-fluid plasmas problems.The numerical flux is constructed by the TENO interpolation of the solution and its derivatives,instead of being reconstructed from the physical flux.The present scheme is used to solve the two sets of Euler equations coupled with Maxwell's equations.The numerical methods are verified by several classical plasma problems.The results show that compared with the original TENO scheme,the present scheme can suppress the non-physical oscillations and reduce the numerical dissipation.展开更多
This paper considers interfacial waves propagating along the interface between a two-dimensional two-fluid with a flat bottom and a rigid upper boundary. There is a light fluid layer overlying a heavier one in the sys...This paper considers interfacial waves propagating along the interface between a two-dimensional two-fluid with a flat bottom and a rigid upper boundary. There is a light fluid layer overlying a heavier one in the system, and a small density difference exists between the two layers. It just focuses on the weakly non-linear small amplitude waves by introducing two small independent parameters： the nonlinearity ratio ε, represented by the ratio of amplitude to depth, and the dispersion ratio μ, represented by the square of the ratio of depth to wave length, which quantify the relative importance of nonlinearity and dispersion. It derives an extended KdV equation of the interfacial waves using the method adopted by Dullin et al in the study of the surface waves when considering the order up to O（μ^2）. As expected, the equation derived from the present work includes, as special cases, those obtained by Dullin et al for surface waves when the surface tension is neglected. The equation derived using an alternative method here is the same as the equation presented by Choi and Camassa. Also it solves the equation by borrowing the method presented by Marchant used for surface waves, and obtains its asymptotic solitary wave solutions when the weakly nonlinear and weakly dispersive terms are balanced in the extended KdV equation.展开更多
The validity of Navier’s partial slip condition is investigated by studying the oscillatory flow in a coated channel.The two-fluid model is used to solve the unsteady viscous equations exactly.Partial slip is experie...The validity of Navier’s partial slip condition is investigated by studying the oscillatory flow in a coated channel.The two-fluid model is used to solve the unsteady viscous equations exactly.Partial slip is experienced by the core fluid.It is found that Naviers condition does not hold for an unsteady core fluid.展开更多
Numerical simulation on the resonant magnetic perturbation penetration is carried out by the newly-updated initial value code MDC(MHD@Dalian Code).Based on a set of two-fluid fourfield equations,the bootstrap current,...Numerical simulation on the resonant magnetic perturbation penetration is carried out by the newly-updated initial value code MDC(MHD@Dalian Code).Based on a set of two-fluid fourfield equations,the bootstrap current,parallel,and perpendicular transport effects are included appropriately.Taking into account the bootstrap current,a mode penetration-like phenomenon is found,which is essentially different from the classical tearing mode model.To reveal the influence of the plasma flow on the mode penetration process,E×B drift flow and diamagnetic drift flow are separately applied to compare their effects.Numerical results show that a sufficiently large diamagnetic drift flow can drive a strong stabilizing effect on the neoclassical tearing mode.Furthermore,an oscillation phenomenon of island width is discovered.By analyzing it in depth,it is found that this oscillation phenomenon is due to the negative feedback regulation of pressure on the magnetic island.This physical mechanism is verified again by key parameter scanning.展开更多
We investigate a two-fluid anisotropic plane symmetric cosmological model with variable gravitational constant G（t） and cosmological term A（t）. In the two-fluid model, one fluid is chosen to be that of the radiati...We investigate a two-fluid anisotropic plane symmetric cosmological model with variable gravitational constant G（t） and cosmological term A（t）. In the two-fluid model, one fluid is chosen to be that of the radiation field modeling the cosmic microwave background and the other one a perfect fluid modeling the material content of the universe. Exact solutions of the field equations are obtained by using a special form for the average scale factor which corresponds to a specific time-varying deceleration parameter. The model obtained presents a cosmological scenario which describes an early acceleration and late-time deceleration. The gravitation constant increases with the cosmic time whereas the cosmological term decreases and asymptotically tends to zero. The physical and kinematical behaviors of the associated fluid parameters are discussed.展开更多
In order to evaluate CCFL （countercurrent flow limitation） characteristics in a PWR （pressurized water reactor） hot leg under reflux condensation, numerical simulations have been conducted using a 2F （two-fluid）...In order to evaluate CCFL （countercurrent flow limitation） characteristics in a PWR （pressurized water reactor） hot leg under reflux condensation, numerical simulations have been conducted using a 2F （two-fluid） model and a VOF （volume of fluid） method implemented in the CFD （computational fluid dynamics） software, FLUENT6.3.26. The 2F model gave good agreement with CCFL data in low pressure conditions but did not give good results for high pressure steam-water conditions. In the previous study, the computational grid and schemes were improved in the VOF method to improve calculations in circular tubes, and the calculated CCFL characteristics agreed well with the UPTF （Upper Plenum Test Facility） data at 1.5 MPa. In this study, therefore, using the 2F model and the computational grid previously improved for the VOF calculations, numerical simulations were conducted for steam-water flows at 1.5 MPa under PWR full-scale conditions. In the range of medium gas volumetric fluxes, the calculated CCFL characteristics agreed well with the values calculated by the VOF method and the UPTF data at 1.5 MPa. This indicated that the reference set of the interfacial drag correlations employed in this study could be applied not only to low pressures but also to high pressures.展开更多
Interracial waves propagating along the interface between a three-dimensional two-fluid system with a rigid upper boundary and an uneven bottom are considered. There is a light fluid layer overlying a heavier one in t...Interracial waves propagating along the interface between a three-dimensional two-fluid system with a rigid upper boundary and an uneven bottom are considered. There is a light fluid layer overlying a heavier one in the system, and a small density difference exists between the two layers. A set of higher-order Boussinesq-type equations in terms of the depth-averaged velocities accounting for stronger nonlinearity are derived. When the small parameter measuring frequency dispersion keeping up to lower-order and full nonlinearity are considered, the equations include the Choi and Camassa＇s results （1999）. The enhanced equations in terms of the depth-averaged velocities are obtained by applying the enhancement technique introduced by Madsen et al. （1991） and Schaffer and Madsen （1995a）. It is noted that the equations derived from the present study include, as special cases, those obtained by Madsen and Schaffer （1998）. By comparison with the dispersion relation of the linear Stokes waves, we found that the dispersion relation is more improved than Choi and Camassa＇s （1999） results, and the applicable scope of water depth is deeper.展开更多
In the paper, we study a compressible two-fluid model in ℝ3, where γ±>1. The pressure of the two fluids is equal. Different from previous research, we consider that viscosity coefficient both μand λare func...In the paper, we study a compressible two-fluid model in ℝ3, where γ±>1. The pressure of the two fluids is equal. Different from previous research, we consider that viscosity coefficient both μand λare functions of density. The global well-posedness of the three-dimensional compressible two-phase flow model is an open problem due to its dissipative, nonlinear structure. In the paper, setting m±=M±and Z=P−P¯, by exploiting the dissipation structure, we obtain energy estimates for (Z,w,n)and its derivatives, then we obtain the time decay rates for (Z,w,n). So we derive global well-posedness and large time behavior to the three dimensional compressible two-fluid model.展开更多
文摘We consider a relativistic two-fluid model of superfluidity,in which the superfluid is described by an order parameter that is a complex scalar field satisfying the nonlinear Klein-Gordon equation(NLKG).The coupling to the normal fluid is introduced via a covariant current-current interaction,which results in the addition of an effective potential,whose imaginary part describes particle transfer between superfluid and normal fluid.Quantized vorticity arises in a class of singular solutions and the related vortex dynamics is incorporated in the modified NLKG,facilitating numerical analysis which is usually very complicated in the phenomenology of vortex filaments.The dual transformation to a string theory description(Kalb-Ramond)of quantum vorticity,the Magnus force,and the mutual friction between quantized vortices and normal fluid are also studied.
基金supported by the National Natural Science Foundation of China(12101095)the Natural Science Foundation of Chongqing(CSTB2022NSCQ-MSX0949,2022NSCQ-MSX2878,CSTC2021jcyj-msxmX0224)+2 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(KJQN202100517,KJQN202300542,KJQN202100511)the Research Project of Chongqing Education Commission(CXQT21014)the grant of Chongqing Young Experts’Workshop.
文摘In this paper,we consider a model of compressible isentropic two-fluid magneto-hydrodynamics without resistivity in a strip domain in three dimensional space.By exploiting the two-tier energy method developed in[Anal PDE,2013,6:1429–1533],we prove the global well-posedness of the governing model around a uniform magnetic field which is non-parallel to the horizontal boundary.Moreover,we show that the solution converges to the steady state at an almost exponential rate as time goes to infinity.Compared to the work of Tan and Wang[SIAM J Math Anal,2018,50:1432–1470],we need to overcome the difficulties caused by particles.
基金Project supported by the National Key Basic Research and Development Program of China(Grant No.2017YFA0304003)the National Natural Science Foundation of China(Grant Nos.U1831202,U1731119,U1931123,11773083,and 11873099)+1 种基金the Chinese Academy of Sciences(Grant Nos.QYZDJ-SSW-SLH043 and GJJSTD20180003)Jiangsu Province,China(Grant No.BRA2020411).
文摘Optical superconducting transition-edge sensor(TES)has been widely used in quantum information,biological imaging,and fluorescence microscopy owing to its high quantum efficiency,low dark count,and photon number resolving capability.The temperature sensitivity(α_(I))and current sensitivity(β_(I))are important parameters for optical TESs,which are generally extracted from the complex impedance.Here we present a method to extractα_(I)andβ_(I)based on a two-fluid model and compare the calculated current-voltage curves,pulse response,and theoretical energy resolution with the measured ones.This method shows qualitative agreement that is suitable for further optimization of optical TESs.
文摘The Quintom dark energy is a proposal that explains the recent observations that mildly favor the equation of state of dark energy ω crossing -1 near the past. The Quintom model is often constructed by two scalar fields, where one is the quintessence feld and another is the phantom field. The cosmological implication of the coupling of the two fields of the dark energy is out of question worth investigating. However, the consideration of the coupling in the field scenario is somewhat complex thus we propose an interacting two-fluid Quintom scenario for simplicity. The interaction between the two components is parametrized by a constant 71 in this scenario. The cosmological implications of this parametrization are investigated in detail in this paper. Also, a diagnostic for this model is performed by using the statefinder pairs {s, r} and {q, r}.
文摘RH vacuum degasser is a very important secondary refining device in the production of high quality steels. The flow field of molten steel in RH system plays a significant role in determining productivity of the equipment. The homogeneous model and VOF method were often used to predict the flow field in RH system, but these kinds of models simplified the interaction between gas bubbles and molten steel. In the present work, a numerical model of a whole RH system, including vacuum degasser, immersed legs and ladle,was built based on gas-liquid two-fluid model, and it could be used to analyze the interaction between argon bubbles and molten steel, to understand the effect of the bubble size to the flow field.
基金Project supported by the National Natural Science Foundation of China(Nos.12072246,11972272,11872286)the National Numerical Wind Tunnel Project of China(No.NNW2020ZT3-A23)。
文摘The weakly ionized plasma flows in aerospace are commonly simulated by the single-fluid model,which cannot describe certain nonequilibrium phenomena by finite collisions of particles,decreasing the fidelity of the solution.Based on an alternative formulation of the targeted essentially non-oscillatory(TENO)scheme,a novel high-order numerical scheme is proposed to simulate the two-fluid plasmas problems.The numerical flux is constructed by the TENO interpolation of the solution and its derivatives,instead of being reconstructed from the physical flux.The present scheme is used to solve the two sets of Euler equations coupled with Maxwell's equations.The numerical methods are verified by several classical plasma problems.The results show that compared with the original TENO scheme,the present scheme can suppress the non-physical oscillations and reduce the numerical dissipation.
文摘This paper considers interfacial waves propagating along the interface between a two-dimensional two-fluid with a flat bottom and a rigid upper boundary. There is a light fluid layer overlying a heavier one in the system, and a small density difference exists between the two layers. It just focuses on the weakly non-linear small amplitude waves by introducing two small independent parameters： the nonlinearity ratio ε, represented by the ratio of amplitude to depth, and the dispersion ratio μ, represented by the square of the ratio of depth to wave length, which quantify the relative importance of nonlinearity and dispersion. It derives an extended KdV equation of the interfacial waves using the method adopted by Dullin et al in the study of the surface waves when considering the order up to O（μ^2）. As expected, the equation derived from the present work includes, as special cases, those obtained by Dullin et al for surface waves when the surface tension is neglected. The equation derived using an alternative method here is the same as the equation presented by Choi and Camassa. Also it solves the equation by borrowing the method presented by Marchant used for surface waves, and obtains its asymptotic solitary wave solutions when the weakly nonlinear and weakly dispersive terms are balanced in the extended KdV equation.
文摘The validity of Navier’s partial slip condition is investigated by studying the oscillatory flow in a coated channel.The two-fluid model is used to solve the unsteady viscous equations exactly.Partial slip is experienced by the core fluid.It is found that Naviers condition does not hold for an unsteady core fluid.
基金supported by the National Key R&D Program of China(No.2022YFE03040001)National Natural Science Foundation of China(Nos.11925501 and 12075048)+1 种基金Chinese Academy of Sciences,Key Laboratory of Geospace Environment,University of Science&Technology of China(No.GE2019-01)Fundamental Research Funds for the Central Universities(No.DUT21GJ204)。
文摘Numerical simulation on the resonant magnetic perturbation penetration is carried out by the newly-updated initial value code MDC(MHD@Dalian Code).Based on a set of two-fluid fourfield equations,the bootstrap current,parallel,and perpendicular transport effects are included appropriately.Taking into account the bootstrap current,a mode penetration-like phenomenon is found,which is essentially different from the classical tearing mode model.To reveal the influence of the plasma flow on the mode penetration process,E×B drift flow and diamagnetic drift flow are separately applied to compare their effects.Numerical results show that a sufficiently large diamagnetic drift flow can drive a strong stabilizing effect on the neoclassical tearing mode.Furthermore,an oscillation phenomenon of island width is discovered.By analyzing it in depth,it is found that this oscillation phenomenon is due to the negative feedback regulation of pressure on the magnetic island.This physical mechanism is verified again by key parameter scanning.
文摘We investigate a two-fluid anisotropic plane symmetric cosmological model with variable gravitational constant G（t） and cosmological term A（t）. In the two-fluid model, one fluid is chosen to be that of the radiation field modeling the cosmic microwave background and the other one a perfect fluid modeling the material content of the universe. Exact solutions of the field equations are obtained by using a special form for the average scale factor which corresponds to a specific time-varying deceleration parameter. The model obtained presents a cosmological scenario which describes an early acceleration and late-time deceleration. The gravitation constant increases with the cosmic time whereas the cosmological term decreases and asymptotically tends to zero. The physical and kinematical behaviors of the associated fluid parameters are discussed.
文摘In order to evaluate CCFL （countercurrent flow limitation） characteristics in a PWR （pressurized water reactor） hot leg under reflux condensation, numerical simulations have been conducted using a 2F （two-fluid） model and a VOF （volume of fluid） method implemented in the CFD （computational fluid dynamics） software, FLUENT6.3.26. The 2F model gave good agreement with CCFL data in low pressure conditions but did not give good results for high pressure steam-water conditions. In the previous study, the computational grid and schemes were improved in the VOF method to improve calculations in circular tubes, and the calculated CCFL characteristics agreed well with the UPTF （Upper Plenum Test Facility） data at 1.5 MPa. In this study, therefore, using the 2F model and the computational grid previously improved for the VOF calculations, numerical simulations were conducted for steam-water flows at 1.5 MPa under PWR full-scale conditions. In the range of medium gas volumetric fluxes, the calculated CCFL characteristics agreed well with the values calculated by the VOF method and the UPTF data at 1.5 MPa. This indicated that the reference set of the interfacial drag correlations employed in this study could be applied not only to low pressures but also to high pressures.
基金Knowledge Innovation Programs of the Chinese Academy of Sciences under contract Nos KZCX2-YW-201 and KZCX1-YW-12Natural Science Fund supported by the Educational Department of Inner Mongolia under contract Nos NJzy080005,and NJ09011A Grant from Science Fund for Young Scholars of Inner Mongolia University under contract NoND0801
文摘Interracial waves propagating along the interface between a three-dimensional two-fluid system with a rigid upper boundary and an uneven bottom are considered. There is a light fluid layer overlying a heavier one in the system, and a small density difference exists between the two layers. A set of higher-order Boussinesq-type equations in terms of the depth-averaged velocities accounting for stronger nonlinearity are derived. When the small parameter measuring frequency dispersion keeping up to lower-order and full nonlinearity are considered, the equations include the Choi and Camassa＇s results （1999）. The enhanced equations in terms of the depth-averaged velocities are obtained by applying the enhancement technique introduced by Madsen et al. （1991） and Schaffer and Madsen （1995a）. It is noted that the equations derived from the present study include, as special cases, those obtained by Madsen and Schaffer （1998）. By comparison with the dispersion relation of the linear Stokes waves, we found that the dispersion relation is more improved than Choi and Camassa＇s （1999） results, and the applicable scope of water depth is deeper.
文摘In the paper, we study a compressible two-fluid model in ℝ3, where γ±>1. The pressure of the two fluids is equal. Different from previous research, we consider that viscosity coefficient both μand λare functions of density. The global well-posedness of the three-dimensional compressible two-phase flow model is an open problem due to its dissipative, nonlinear structure. In the paper, setting m±=M±and Z=P−P¯, by exploiting the dissipation structure, we obtain energy estimates for (Z,w,n)and its derivatives, then we obtain the time decay rates for (Z,w,n). So we derive global well-posedness and large time behavior to the three dimensional compressible two-fluid model.
