By studying of a slender body moving in a fluid wave-medium, e.g., in air or in shallow water, it was found that the hydrodynamic momentum mass and the total energy of the fluid field can be expressed in forms of and ...By studying of a slender body moving in a fluid wave-medium, e.g., in air or in shallow water, it was found that the hydrodynamic momentum mass and the total energy of the fluid field can be expressed in forms of and E=mc<sup>2</sup>, where v is the body moving speed, c is the wave speed and is the hydrodynamic mass at the zero speed. Thus a hydrodynamic analogy to the relativistic particle motion in vacuum can be traced. The velocity dependence of mass and the mass-energy equivalence are universal for any wave medium, which should not be regarded as a consequence of relative Lorentz time-space, but one of the existence of wave in the medium. Its further inference leads to an even more significant physical picture. If the mass particle moves in an unbounded space at a supercritical speed, i.e. , waves are generated and radiated from it, like the Mach waves by the supersonic plane, and the particle itself experiences a resistance as reaction from the wave radiation. By an extension of this analogy, it can be interred from a hydrodynamic superconductive phenomenon that particles or waves can move possibly at a superluminal speed without experiencing any resistance through a tunnel (a bounded space) under certain conditions. Therefore the speed of light is not the limit of our physical world and superluminal phenomena are possible.展开更多
Spectral and timing properties of accretion flows on a black hole depend on their density and temperature distributions,which in turn come from the underlying dynamics.Thus,an accurate description of the flow which in...Spectral and timing properties of accretion flows on a black hole depend on their density and temperature distributions,which in turn come from the underlying dynamics.Thus,an accurate description of the flow which includes hydrodynamics and radiative transfer is a must to interpret the observational results.In the case of nonrotating black holes,a pseudo-Newtonian description of surrounding spacetime enables one to make significant progress in predicting spectral and timing properties.This formalism is lacking for spinning black holes.In this paper,we show that there exists an exact form of a"natural"potential derivable from the general relativistic(GR)radial momentum equation.Use of this potential in an otherwise Newtonian set of equations allows to describe transonic flows very accurately as is evidenced by comparing with solutions obtained from the full GR framework.We study the properties of the critical points and the centrifugal pressure supported shocks in the parameter space spanned by the specific energy and angular momentum,and compare with the results of GR hydrodynamics.We show that this potential can safely be used for the entire range of Kerr parameter-1<a<1 for modeling of observational results around spinning black holes.We assume the flow to be inviscid.Thus,it is non-dissipative with constant energy and angular momentum.These assumptions are valid very close to the black hole as the infall timescale is much shorter as compared to the viscous timescale.展开更多
Based on hydrodynamic model tests, the relationship between relative hydrodynamic coefficient and cycle coefficient K-c is obtained by introducing the relative trench shape coefficient a(r); there isa good relation fo...Based on hydrodynamic model tests, the relationship between relative hydrodynamic coefficient and cycle coefficient K-c is obtained by introducing the relative trench shape coefficient a(r); there isa good relation for the shallow trench. According to a(r) of the designed trench shape and pre-chosen K-c, the reduction coefficient and sheltering effect can be decided by the result provided in this paper.展开更多
Optical and radio afterglows arising from shocks by relativistic conical ejecta running into pre-burst massive stellar winds are revisited. Under the homogeneous thin-shell approximation and a realistic treatment for ...Optical and radio afterglows arising from shocks by relativistic conical ejecta running into pre-burst massive stellar winds are revisited. Under the homogeneous thin-shell approximation and a realistic treatment for the lateral expansion of jets, our results show that a notable break exists in the optical light curve in most cases we calculated in which the physical parameters are varied within reasonable ranges. For a relatively tenuous wind which cannot decelerate the relativistic jet to cause a light curve break within days, the wind termination shock due to the ram pressure of the surrounding medium occurs at a small radius, namely, a few times 10<SUP>17</SUP> cm. In such a structured wind environment, the jet will pass through the wind within several hours and run into the outer uniform dense medium. The resulting optical light curve flattens with a shallower drop after the jet encounters the uniform medium, and then declines deeply, triggered by runaway lateral expansion.展开更多
文摘By studying of a slender body moving in a fluid wave-medium, e.g., in air or in shallow water, it was found that the hydrodynamic momentum mass and the total energy of the fluid field can be expressed in forms of and E=mc<sup>2</sup>, where v is the body moving speed, c is the wave speed and is the hydrodynamic mass at the zero speed. Thus a hydrodynamic analogy to the relativistic particle motion in vacuum can be traced. The velocity dependence of mass and the mass-energy equivalence are universal for any wave medium, which should not be regarded as a consequence of relative Lorentz time-space, but one of the existence of wave in the medium. Its further inference leads to an even more significant physical picture. If the mass particle moves in an unbounded space at a supercritical speed, i.e. , waves are generated and radiated from it, like the Mach waves by the supersonic plane, and the particle itself experiences a resistance as reaction from the wave radiation. By an extension of this analogy, it can be interred from a hydrodynamic superconductive phenomenon that particles or waves can move possibly at a superluminal speed without experiencing any resistance through a tunnel (a bounded space) under certain conditions. Therefore the speed of light is not the limit of our physical world and superluminal phenomena are possible.
基金sponsored RESPOND project(ISRO/RES/2/418/18-19)supported in part by the Higher Education Dept.of the Govt.of West Bengal,India。
文摘Spectral and timing properties of accretion flows on a black hole depend on their density and temperature distributions,which in turn come from the underlying dynamics.Thus,an accurate description of the flow which includes hydrodynamics and radiative transfer is a must to interpret the observational results.In the case of nonrotating black holes,a pseudo-Newtonian description of surrounding spacetime enables one to make significant progress in predicting spectral and timing properties.This formalism is lacking for spinning black holes.In this paper,we show that there exists an exact form of a"natural"potential derivable from the general relativistic(GR)radial momentum equation.Use of this potential in an otherwise Newtonian set of equations allows to describe transonic flows very accurately as is evidenced by comparing with solutions obtained from the full GR framework.We study the properties of the critical points and the centrifugal pressure supported shocks in the parameter space spanned by the specific energy and angular momentum,and compare with the results of GR hydrodynamics.We show that this potential can safely be used for the entire range of Kerr parameter-1<a<1 for modeling of observational results around spinning black holes.We assume the flow to be inviscid.Thus,it is non-dissipative with constant energy and angular momentum.These assumptions are valid very close to the black hole as the infall timescale is much shorter as compared to the viscous timescale.
文摘Based on hydrodynamic model tests, the relationship between relative hydrodynamic coefficient and cycle coefficient K-c is obtained by introducing the relative trench shape coefficient a(r); there isa good relation for the shallow trench. According to a(r) of the designed trench shape and pre-chosen K-c, the reduction coefficient and sheltering effect can be decided by the result provided in this paper.
基金Supported by the National Natural Science Foundation of China.
文摘Optical and radio afterglows arising from shocks by relativistic conical ejecta running into pre-burst massive stellar winds are revisited. Under the homogeneous thin-shell approximation and a realistic treatment for the lateral expansion of jets, our results show that a notable break exists in the optical light curve in most cases we calculated in which the physical parameters are varied within reasonable ranges. For a relatively tenuous wind which cannot decelerate the relativistic jet to cause a light curve break within days, the wind termination shock due to the ram pressure of the surrounding medium occurs at a small radius, namely, a few times 10<SUP>17</SUP> cm. In such a structured wind environment, the jet will pass through the wind within several hours and run into the outer uniform dense medium. The resulting optical light curve flattens with a shallower drop after the jet encounters the uniform medium, and then declines deeply, triggered by runaway lateral expansion.
