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P B Ivanov - One of the best experts on this subject based on the ideXlab platform.
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a fully relativistic twisted disc around a slowly rotating kerr black hole derivation of dynamical equations and the shape of stationary configurations
Monthly Notices of the Royal Astronomical Society, 2011Co-Authors: V V Zhuravlev, P B IvanovAbstract:In this paper we derive equations describing the dynamics and stationary configurations of a twisted fully relativistic thin accretion disc around a slowly rotating black hole. We assume that the inclination angle of the disc is small and that the standard relativistic generalization of the α model of accretion discs is valid when the disc is flat. We find that similar to the case of non-relativistic twisted discs the disc dynamics and stationary shapes can be determined by a pair of equations formulated for two complex variables describing the orientation of the disc rings and velocity perturbations induced by the twist. We analyse analytically and numerically the shapes of stationary twisted configurations of accretion discs having non-zero inclinations with respect to the black hole equatorial plane at large distances r from the black hole. It is shown that the stationary configurations depend on two Parameters – the viscosity Parameter α and the Parameter , where δ* is the opening angle (δ*∼h/r, where h is the disc half-thickness and r is large) of a flat disc and a is the black hole Rotational Parameter. When a > 0 and the shapes depend drastically on the value of α. When α is small the disc inclination angle oscillates with radius with amplitude and radial frequency of the oscillations dramatically increasing towards the last stable orbit, Rms. When α has a moderately small value the oscillations do not take place but the disc does not align with the equatorial plane at small radii. The disc inclination angle either is increasing towards Rms or exhibits a non-monotonic dependence on the radial coordinate. Finally, when α is sufficiently large the disc aligns with the equatorial plane at small radii. When a < 0 the disc aligns with the equatorial plane for all values of α. The results reported here may have implications for determining the structure and variability of accretion discs close to Rms as well as for modelling of emission spectra coming from different sources, which are supposed to contain black holes.
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relativistic cross sections of mass stripping and tidal disruption of a star by a super massive rotating black hole
Astronomy and Astrophysics, 2006Co-Authors: P B Ivanov, M ChernyakovaAbstract:Aims. We consider the problem of tidal disruption of a star by a super-massive rotating black hole. Methods. Using a numerically fast Lagrangian model of a tidally disrupted star developed in our previous works, we survey the Parameter space of the problem and find regions where the total disruption of the star or a partial mass loss from the star takes place as a result of fly-by around the black hole. Our treatment is based on General Relativity, and we consider a range of black hole masses where the tidal disruption competes with the relativistic effect of direct capture of stars by the black hole. We model the star as a full polytrope with n = 1.5 with the solar mass and radius. We show that our results can also be used to obtain the amount of mass lost by stars with different stellar masses and radii. Results. We find that the results can be conveniently represented on the plane of specific orbital angular momenta of the star (j θ , j Φ ). We calculate the contours of a given mass loss of the star on this plane, for a given black hole mass M, Rotational Parameter a and inclination of the trajectory of the star with respect to the black hole equatorial plane. In the following such contours are referred to as the tidal cross sections. It is shown that the tidal cross sections can be approximated as circles symmetric above the axis j Φ = 0, and shifted with respect to the origin of the coordinates in the direction of negative j θ . The radii and shifts of these circles are obtained numerically for the black hole masses in the range 5 × 10 5 M Θ -10 9 M Θ and different values of a. It is shown that when a = 0 tidal disruption takes place for M < 5 x 10 7 M Θ and when a ≈ 1 tidal disruption is possible for M < 10 9 M Θ .
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relativistic cross sections of mass stripping and tidal disruption of a star by a super massive rotating black hole
arXiv: Astrophysics, 2005Co-Authors: P B Ivanov, M ChernyakovaAbstract:[abbreviated] We consider the problem of tidal disruption of a star by a super-massive Kerr black hole. Using a numerically fast Lagrangian model of the tidally disrupted star we survey the Parameter space of the problem and find the regions in the Parameter space where the total disruption of the star or a partial mass loss take place as a result of fly-by around the black hole. Our treatment is based on General Relativity, and we consider the range of the black hole masses where the tidal disruption competes with the relativistic effect of direct capture of the star by the black hole. We find that our results can be represented on the plane of specific orbital angular momenta of the star $(j_{\theta}, j_{\phi})$. We calculate the contours of a given mass loss of the star on this plane, referred to as the tidal cross sections, for a given black hole mass $M$, Rotational Parameter $a$ and inclination of the trajectory of the star with respect to the black hole equatorial plane. It is shown that the tidal cross sections can be approximated as circles symmetric above the axis $j_{\phi}=0$, and shifted with respect to the origin of the coordinates in direction of negative $j_{\theta}$. The radii and shifts of these circles are obtained numerically for the black hole masses in the range $5\cdot 10^{5}M_{\odot}-10^{9}M_{\odot}$ and different values of $a$. It is shown that when $a=0$ the tidal disruption takes place for $M < 5\cdot 10^{7}M_{\odot}$ and when $a\approx 1$ the tidal disruption is possible for $M < 10^{9}M_{\odot}$.
M Chernyakova - One of the best experts on this subject based on the ideXlab platform.
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relativistic cross sections of mass stripping and tidal disruption of a star by a super massive rotating black hole
Astronomy and Astrophysics, 2006Co-Authors: P B Ivanov, M ChernyakovaAbstract:Aims. We consider the problem of tidal disruption of a star by a super-massive rotating black hole. Methods. Using a numerically fast Lagrangian model of a tidally disrupted star developed in our previous works, we survey the Parameter space of the problem and find regions where the total disruption of the star or a partial mass loss from the star takes place as a result of fly-by around the black hole. Our treatment is based on General Relativity, and we consider a range of black hole masses where the tidal disruption competes with the relativistic effect of direct capture of stars by the black hole. We model the star as a full polytrope with n = 1.5 with the solar mass and radius. We show that our results can also be used to obtain the amount of mass lost by stars with different stellar masses and radii. Results. We find that the results can be conveniently represented on the plane of specific orbital angular momenta of the star (j θ , j Φ ). We calculate the contours of a given mass loss of the star on this plane, for a given black hole mass M, Rotational Parameter a and inclination of the trajectory of the star with respect to the black hole equatorial plane. In the following such contours are referred to as the tidal cross sections. It is shown that the tidal cross sections can be approximated as circles symmetric above the axis j Φ = 0, and shifted with respect to the origin of the coordinates in the direction of negative j θ . The radii and shifts of these circles are obtained numerically for the black hole masses in the range 5 × 10 5 M Θ -10 9 M Θ and different values of a. It is shown that when a = 0 tidal disruption takes place for M < 5 x 10 7 M Θ and when a ≈ 1 tidal disruption is possible for M < 10 9 M Θ .
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relativistic cross sections of mass stripping and tidal disruption of a star by a super massive rotating black hole
arXiv: Astrophysics, 2005Co-Authors: P B Ivanov, M ChernyakovaAbstract:[abbreviated] We consider the problem of tidal disruption of a star by a super-massive Kerr black hole. Using a numerically fast Lagrangian model of the tidally disrupted star we survey the Parameter space of the problem and find the regions in the Parameter space where the total disruption of the star or a partial mass loss take place as a result of fly-by around the black hole. Our treatment is based on General Relativity, and we consider the range of the black hole masses where the tidal disruption competes with the relativistic effect of direct capture of the star by the black hole. We find that our results can be represented on the plane of specific orbital angular momenta of the star $(j_{\theta}, j_{\phi})$. We calculate the contours of a given mass loss of the star on this plane, referred to as the tidal cross sections, for a given black hole mass $M$, Rotational Parameter $a$ and inclination of the trajectory of the star with respect to the black hole equatorial plane. It is shown that the tidal cross sections can be approximated as circles symmetric above the axis $j_{\phi}=0$, and shifted with respect to the origin of the coordinates in direction of negative $j_{\theta}$. The radii and shifts of these circles are obtained numerically for the black hole masses in the range $5\cdot 10^{5}M_{\odot}-10^{9}M_{\odot}$ and different values of $a$. It is shown that when $a=0$ the tidal disruption takes place for $M < 5\cdot 10^{7}M_{\odot}$ and when $a\approx 1$ the tidal disruption is possible for $M < 10^{9}M_{\odot}$.
Shuzheng Yang - One of the best experts on this subject based on the ideXlab platform.
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fermions tunneling of higher dimensional kerr anti de sitter black hole with one Rotational Parameter
Physics Letters B, 2009Co-Authors: Kai Lin, Shuzheng YangAbstract:Abstract The 1/2 spin fermions tunneling at the horizon of n-dimensional Kerr–Anti-de Sitter black hole with one Rotational Parameter is researched via semi-classical approximation method, and the Hawking temperature and fermions tunneling rate are obtained in this Letter. Using a new method, the semi-classical Hamilton–Jacobi equation is gotten from the Dirac equation in this Letter, and the work makes several quantum tunneling theories more harmonious.
Tasawar Hayat - One of the best experts on this subject based on the ideXlab platform.
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numerical simulation for darcy forchheimer 3d rotating flow subject to binary chemical reaction and arrhenius activation energy
Journal of Central South University, 2019Co-Authors: Tasawar Hayat, Arsalan Aziz, Taseer Muhammad, Ahmed AlsaediAbstract:Three-dimensional Darcy-Forchheimer nanoliquid flow in the presence of rotating frame and activation energy is inspected. Flow is developed through linearly stretching of the surface. Convection of heat and mass exchange is given due consideration. The novel characteristics in regards to Brownian dispersion and thermophoresis are retained. The variation in partial differential framework (PDEs) to nonlinear ordinary differential framework (ODEs) is done through reasonable transformations. Governing differential frameworks have been computed in edge of NDSolve. Discussion regarding thermal field and concentration distribution for several involved Parameters is pivotal part. Physical amounts like surface drag coefficients, transfer of heat and mass rates are portrayed by numeric esteems. It is noticed that impacts of porosity Parameter and Forchheimer number on the thermal and concentration fields are quite similar. Both temperature and associated thermal layer thickness are enhanced for larger porosity Parameter and Forchheimer number. Temperature and concentration fields exhibit similar trend for the higher values of Rotational Parameter. Effects of thermal and concentration Biot numbers on the temperature and concentration fields are qualitatively similar. Higher Prandtl and Schmidt numbers correspond to stronger temperature and concentration fields. Larger nondimensional activation energy, temperature difference Parameter and fitted rate constant yield weaker concentration field. Brownian motion Parameter for temperature and concentration has reverse effects while similar trend is observed via thermophoresis Parameter.
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entropy generation minimization and statistical declaration with probable error for skin friction coefficient and nusselt number
Chinese Journal of Physics, 2018Co-Authors: Muhammad Ijaz Khan, Tasawar Hayat, Sumaira Qayyum, A AlsaediAbstract:Abstract Main emphasis of present work is to analyze the novel feature of entropy generation in MHD nanomaterial flow between two rotating disks. Heat transfer process is explored in the presence of Joule heating and thermal radiation. Tiwari–Das nanofluid model is employed in mathematical modeling. Aluminum oxide and copper water nanoparticles are accounted. Statistical declaration and probable error for problem accuracy are computed. Total entropy generation subject to Bejan number is scrutinized. Suitable variables are utilized to transform nonlinear PDEs to ordinary ones. Convergent series solutions are computed. Zeroth and mth order problems are discussed for stability analysis. The impact of physical flow variables like Reynolds number, magnetic Parameter, porosity Parameter, stretching Parameter, Rotational Parameter, radiation Parameter, Eckert number, suction injection Parameter, Brinkman number and temperature ratio Parameter on velocities, temperature, total entropy generation and Bejan number are examined and discussed through graphs. Velocity and thermal gradients at the surface of disks are computed.
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current progresses about probable error and statistical declaration for radiative two phase flow using ag h 2 o and cu h 2 o nanomaterials
International Journal of Hydrogen Energy, 2017Co-Authors: Tasawar Hayat, Sumaira Qayyum, Muhammad Ijaz Khan, Ahmed AlsaediAbstract:Abstract Here modeling and computations are presented to introduce the novel concept of statistical declaration and probable error for radiative flow between two stretchable rotating disks. Effects of Joule heating and thermal radiation are accounted. Homogenous and heterogeneous reactions are also implemented. The thermophysical characteristics of nanofluids are scrutinized using silver and copper nanoparticles. Statistical declaration and probable error for coefficient of skin friction and heat transfer rate are calculated. System of nonlinear ordinary differential equations is obtained by using appropriate variables. Convergent solutions of the involved problems are obtained and discussed. Skin friction coefficient and Nusselt number are calculated and discussed. Radial and axial velocities have opposite impact for stretching Parameters of lower and upper disks. Concentration decays for both Schmidt number and homogeneous reaction variable. Coefficient of skin friction is less for larger Rotational Parameter at both disks. Opposite behavior of heat transfer rate is observed at lower and upper disks for increasing Eckert number. For limiting cases comparisons with previously available results [23,52,53] in the literature are made and an excellent agreement is noticed.
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flow between two stretchable rotating disks with cattaneo christov heat flux model
Results in physics, 2017Co-Authors: Tasawar Hayat, Sumaira Qayyum, Maria Imtiaz, Ahmed AlsaediAbstract:Abstract An analysis is performed to investigate flow between two stretchable rotating disks. Thermal equation is constructed by Cattaneo-Christov heat flux theory. Porous medium is also taken into account. The nonlinear partial differential equations are first converted to ordinary differential equations and then computed for the convergent series solutions. Discussion about impact of dimensionless Parameters on velocities, temperature and skin friction coefficient is given. It is observed that the radial velocity at upper disk enhances for larger values of ratio of corresponding stretching rate to angular velocity. Velocity in y-direction decays with an increase in Rotational Parameter. Magnitude of temperature profile decays for larger Prandtl number and thermal relaxation Parameter.
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mhd flow and heat transfer between coaxial rotating stretchable disks in a thermally stratified medium
PLOS ONE, 2016Co-Authors: Tasawar Hayat, Sumaira Qayyum, Maria Imtiaz, Ahmed AlsaediAbstract:This paper investigates the unsteady MHD flow of viscous fluid between two parallel rotating disks. Fluid fills the porous space. Energy equation has been constructed by taking Joule heating, thermal stratification and radiation effects into consideration. We convert system of partial differential equations into system of highly nonlinear ordinary differential equations after employing the suitable transformations. Convergent series solutions are obtained. Behavior of different involved Parameters on velocity and temperature profiles is examined graphically. Numerical values of skin friction coefficient and Nusselt number are computed and inspected. It is found that tangential velocity profile is increasing function of Rotational Parameter. Fluid temperature reduces for increasing values of thermal stratification Parameter. At upper disk heat transfer rate enhances for larger values of Eckert and Prandtl numbers.
Kai Lin - One of the best experts on this subject based on the ideXlab platform.
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fermions tunneling of higher dimensional kerr anti de sitter black hole with one Rotational Parameter
Physics Letters B, 2009Co-Authors: Kai Lin, Shuzheng YangAbstract:Abstract The 1/2 spin fermions tunneling at the horizon of n-dimensional Kerr–Anti-de Sitter black hole with one Rotational Parameter is researched via semi-classical approximation method, and the Hawking temperature and fermions tunneling rate are obtained in this Letter. Using a new method, the semi-classical Hamilton–Jacobi equation is gotten from the Dirac equation in this Letter, and the work makes several quantum tunneling theories more harmonious.
