Finite Difference Theory Research Articles

A numerical method for solving the neutrino Boltzmann equation coupled to spherically symmetric stellar core collapse

view Abstract Citations (166) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Numerical Method for Solving the Neutrino Boltzmann Equation Coupled to Spherically Symmetric Stellar Core Collapse Mezzacappa, Anthony ; Bruenn, Stephen W. Abstract A numerical method for solving the Boltzmann equation coupled to hydrodynamic flows, a relativistic equation of state, and lepton conservation for fermion transport has been developed. Difficulties encountered in past attempts to solve the neutron Boltzmann equation in stellar cores have been overcome. In particular, the correct diffusion limit for optically thick zones has been obtained without introducing ad hoc factors in the radial transport term. Oscillations in the neutrino distribution function in optically thin zones have been avoided. New numerical techniques for the angular aberration and frequency shift terms have been developed and successfully implemented. In particular, a finite difference representation has been developed for the angular aberration term that can be used with Gaussian quadratures and Bruenn's method has been successfully generated for the frequency shift term. Publication: The Astrophysical Journal Pub Date: March 1993 DOI: 10.1086/172395 Bibcode: 1993ApJ...405..669M Keywords: Boltzmann Transport Equation; Computational Astrophysics; Finite Difference Theory; Gravitational Collapse; Neutrinos; Stellar Cores; Hydrodynamics; Newton-Raphson Method; Radiation Transport; Symmetry; Astrophysics; ELEMENTARY PARTICLES; STARS: INTERIORS; STARS: SUPERNOVAE: GENERAL full text sources ADS |

A powerful local shear instability in weakly magnetized disks. III - Long-term evolution in a shearing sheet. IV - Nonaxisymmetric perturbations

view Abstract Citations (216) References (23) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Powerful Local Shear Instability in Weakly Magnetized Disks. III. Long-Term Evolution in a Shearing Sheet Hawley, John F. ; Balbus, Steven A. Abstract The nonlinear evolution of the recently identified accretion disk magnetic shear instability is investigated through a series of numerical simulations. Finite-difference computations of the equations of compressible MHD are carried out on an axisymmetric shearing sheet system with periodic boundary conditions designed to approximate a local region within an accretion disk. Initial field configurations that include some net vertical component evolve into a nonlinear, exponentially growing solution with large poloidal velocities and magnetic fields with energies comparable to the thermal energy density. The stability of a purely azimuthal field configuration is examined, and it is found that nonaxisymmetric instability is present, but with a growth time measured in tens of orbital periods. In general, the most rapid growth occurs for very small radial and azimuthal wavenumbers, leading to coherent magnetic field structure in planes parallel to the disk. It is suggested that this instability is a key ingredient for the generation of magnetic fields in disks. Publication: The Astrophysical Journal Pub Date: December 1992 DOI: 10.1086/172021 Bibcode: 1992ApJ...400..595H Keywords: Accretion Disks; Angular Momentum; Magnetic Field Configurations; Magnetohydrodynamic Stability; Nonlinear Evolution Equations; Computer Animation; Finite Difference Theory; Shear Flow; Astrophysics; ACCRETION; ACCRETION DISKS; INSTABILITIES; MAGNETOHYDRODYNAMICS: MHD full text sources ADS | Related Materials (3) Part 1: 1991ApJ...376..214B Part 2: 1991ApJ...376..223H Part 4: 1992ApJ...400..610B

ZEUS-2D: A radiation magnetohydrodynamics code for astrophysical flows in two space dimensions. I - The hydrodynamic algorithms and tests. II - The magnetohydrodynamic algorithms and tests

view Abstract Citations (1325) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS ZEUS-2D: A Radiation Magnetohydrodynamics Code for Astrophysical Flows in Two Space Dimensions. I. The Hydrodynamic Algorithms and Tests Stone, James M. ; Norman, Michael L. Abstract A detailed description of ZEUS-2D, a numerical code for the simulation of fluid dynamical flows including a self-consistent treatment of the effects of magnetic fields and radiation transfer is presented. Attention is given to the hydrodynamic (HD) algorithms which form the foundation for the more complex MHD and radiation HD algorithms. The effect of self-gravity on the flow dynamics is accounted for by an iterative solution of the sparse-banded matrix resulting from discretizing the Poisson equation in multidimensions. The results of an extensive series of HD test problems are presented. A detailed description of the MHD algorithms in ZEUS-2D is presented. A new method of computing the electromotive force is developed using the method of characteristics (MOC). It is demonstrated through the results of an extensive series of MHD test problems that the resulting hybrid MOC-constrained transport method provides for the accurate evolution of all modes of MHD wave families. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1992 DOI: 10.1086/191680 Bibcode: 1992ApJS...80..753S Keywords: Computational Astrophysics; Cosmic Plasma; Hydrodynamic Equations; Magnetohydrodynamic Flow; Self Consistent Fields; Computational Grids; Finite Difference Theory; Plasma Radiation; Poisson Equation; Radiative Transfer; Astrophysics; HYDRODYNAMICS; MAGNETOHYDRODYNAMICS: MHD; METHODS: NUMERICAL; RADIATIVE TRANSFER full text sources ADS | Related Materials (3) Described in: 1992ApJS...80..791S Described in: 1992ApJS...80..819S Source Software: 2013ascl.soft06014S

ZEUS-2D: A radiation magnetohydrodynamics code for astrophysical flows in two space dimensions. III - The radiation hydrodynamic algorithms and tests

view Abstract Citations (238) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS ZEUS-2D: A Radiation Magnetohydrodynamics Code for Astrophysical Flows in Two Space Dimensions. III. The Radiation Hydrodynamic Algorithms and Tests Stone, James M. ; Mihalas, Dimitri ; Norman, Michael L. Abstract The radiation hydrodynamical (RHD) algorithms in ZEUS-2D are described. These algorithms use a tensor variable Eddington factor, computed from a solution of the static transfer equation, to close the system of radiation moment equations. This full transport algorithm, which differs significantly from more commonly used methods based on the diffusion approximation, is applicable in both optically thin and thick media. Results computed by these algorithms on a new collection of RHD test problems are presented. For the transfer equation, very detailed tests are possible which compare the numerical solution for the specific intensity at every point on a given tangent plane to the known analytic solution. It is shown that, while the interpolation inherent in the method of short characteristics makes the solution diffusive, it is not overly so. For certain restricted geometries and physical conditions, these methods reproduce the expected results either identically or qualitatively. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1992 DOI: 10.1086/191682 Bibcode: 1992ApJS...80..819S Keywords: Computational Astrophysics; Cosmic Plasma; Hydrodynamic Equations; Magnetohydrodynamic Flow; Radiative Transfer; Two Dimensional Models; Algorithms; Computational Grids; Finite Difference Theory; Plasma Radiation; Astrophysics; HYDRODYNAMICS; MAGNETOHYDRODYNAMICS: MHD; METHODS: NUMERICAL; RADIATIVE TRANSFER full text sources ADS | Related Materials (3) Described in: 1992ApJS...80..753S Described in: 1992ApJS...80..791S Source Software: 2013ascl.soft06014S

Fragmentation of elongated cylindrical clouds. I - Isothermal clouds

view Abstract Citations (70) References (29) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Fragmentation of Elongated Cylindrical Clouds. I. Isothermal Clouds Bastien, Pierre ; Arcoragi, Jean-Pierre ; Benz, Willy ; Bonnell, Ian ; Martel, Hugo Abstract A numerical study is presented of fragmentation in its simplest possible form: that of elongated, isothermal, axially symmetric clouds. Results have been obtained for different ratios of length to diameter, L/D, and initial Jeans numbers, J0 (ratio of gravitational to thermal energies). Initial density perturbations are introduced on the axis of otherwise uniformly dense cylinders, and the maximum number of fragments Nf(max) that can form and grow for combinations of L/D and J0 is determined. The value of Nf(max) increases with J0 at small J0, then saturates at a finite value Nf(max) about 2L/D at large J0. That results contradicts analytical predictions based on a linear stability analysis for infinite cylinders or the ratio of the total mass to the Jeans mass. The results are directly applicable to observations of the cores of dark molecular clouds which are found to be mostly prolate. These cores are then expected to fragment and form stars in multiple systems or in small groups, as frequently observed in star-forming regions. Publication: The Astrophysical Journal Pub Date: September 1991 DOI: 10.1086/170424 Bibcode: 1991ApJ...378..255B Keywords: Molecular Clouds; Nebulae; Star Formation; Cylindrical Bodies; Finite Difference Theory; Hydrodynamics; Poisson Equation; Astrophysics; HYDRODYNAMICS; NEBULAE: GENERAL; NUMERICAL METHODS; STARS: FORMATION full text sources ADS | Related Materials (5) Part 2: 1991ApJ...380..476A Part 3: 1991ApJ...377..553B Part 4: 1992ApJ...400..579B Part 5: 1992ApJ...401..654B Part 6: 1993ApJ...406..614B

Simplified thermal analysis of naturally ventilated dwellings

A simplified comprehensive methodology for thermal comfort prediction in a naturally crossventilated room is described. The methodology mainly consists of the following three steps: • - analysis of the dynamic thermal behaviour of the given room, by means of the admittance procedure; • - evaluation of the air flows rates and their velocities in the room, by means of a new simplified method; • - thermal comfort prediction by means of the Fanger's theory. The results obtained appear satisfactory and the simplified methodology makes itself a useful tool for the identification of appropriate choices at the early stages of the design process, regarding naturally ventilated buildings. Therma comfort conditions, referred to global comfort situations, for people living inside the dwellings are especially taken into account. Through the paper, a validation against experimental data is presented, with respect to the inside air velocity. Moreover, the simplified procedure here introduced and based on the admittance method, is compared with a more sophisticated simulation model, developed following the finite difference theory, for various buildings driven by the climatic data of Rome.

Theoretical light curve of SN 1987A and mixing of hydrogen and nickel in the ejecta

view Abstract Citations (304) References (62) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Theoretical Light Curve of SN 1987A and Mixing of Hydrogen and Nickel in the Ejecta Shigeyama, Toshikazu ; Nomoto, Ken'ichi Abstract Refined light curve models for SN 1987A are presented. Improvements are due to the presupernova models taken from the evolutionary calculations and the postexplosion abundance distribution in the ejecta as inferred from the X-ray and γ-ray light curves. We have found the following effects of material mixing in the ejecta on the light curve shape. Radioactive materials mixed into the surface layer with the expansion velocity of ~ 3000 km s^-1^ provide energy to increase the luminosity after ~ day 25; this accounts for the observed light curve and the Bochum event. Mixing of hydrogen into the core shows a significant effect on the light curve, since the hydrogen recombination wave plays an essential role in forming a plateau-like peak of the light curve. The calculated plateau is broader if the minimum velocity of the hydrogen layer ν^H^_min_ is lower, i.e., if hydrogen is mixed into the deeper core. For ν^H^_min_ ~ 800 km s^- 1^, the calculated light curve is successful in reproducing the broad peak from ~ day 60-100. With such mixing of hydrogen and ^56^Ni, the theoretical light curve is in good agreement with the observation if the ratio between the explosion energy and the mass of the hydrogen- rich envelope is E/M_env_ = (1.1 +/- 0.3) x 50^50^ ergs M^-1^_sun_. The light curves of other Type II supernovae are also discussed in terms of ν^H^_min_. Publication: The Astrophysical Journal Pub Date: September 1990 DOI: 10.1086/169114 Bibcode: 1990ApJ...360..242S Keywords: Interstellar Chemistry; Light Curve; Metallicity; Stellar Mass Ejection; Stellar Models; Supernova 1987a; Finite Difference Theory; Hydrogen; Nickel; Stellar Luminosity; Thermodynamic Equilibrium; Astrophysics; HYDRODYNAMICS; RADIATIVE TRANSFER; STARS: INDIVIDUAL ALPHANUMERIC: SN 1987A; STARS: INTERIORS; STARS: SUPERNOVAE full text sources ADS | data products NED (2) SIMBAD (1)

Hollow conical jet models for SS 433 - A paradigm lost?

view Abstract Citations (20) References (21) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hollow Conical Jet Models for SS 433: A Paradigm Lost? Kochanek, Christopher S. ; Hawley, John F. Abstract A precessing jet such as that in SS 433 may be approximated as an axisymmetric flow, if the precession time is short by comparison to the propagation time. A series of simulations has been conducted for precessing jets using an axisymmetric finite-difference hydrodynamics code. Examinations are made of hollow cylindrical jets, which lack the complication of a growing interior volume, and conical jets, which model the behavior of a precessing jet propagating on the surface of its precession cone. Publication: The Astrophysical Journal Pub Date: February 1990 DOI: 10.1086/168411 Bibcode: 1990ApJ...350..561K Keywords: Astronomical Models; Computational Astrophysics; Eclipsing Binary Stars; Radio Jets (Astronomy); Bow Waves; Emission Spectra; Finite Difference Theory; Precession; Shock Waves; Supernova Remnants; Astrophysics; GALAXIES: JETS; HYDRODYNAMICS; NEBULAE: INDIVIDUAL ALPHANUMERIC: W50; STARS: INDIVIDUAL ALPHANUMERIC: SS 433 full text sources ADS | data products SIMBAD (2)

Analysis of material interface discontinuities and superconvergent fluxes in finite difference theory

An analysis of material interface discontinuities is developed and applied in finite difference theory to determine mathematically rigorous averaging techniques for material properties. This result is compared with other averaging techniques, particularly harmonic averaging, which is often applied in practice. We also develop a class of formulas of high accuracy for post-processing the difference formula to compute derivatives (fluxes, stresses), and conduct supporting numerical studies.

Radiation-hydrodynamic calculation of sub-Eddington accretion disks

view Abstract Citations (39) References (22) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radiation-Hydrodynamic Calculation of Sub-Eddington Accretion Disks Eggum, G. E. ; Coroniti, F. V. ; Katz, J. I. Abstract The authors report the results of self-consistent, azimuthally symmetric, radiation-hydrodynamic calculations of subcritical accretion disks about a Newtonian pseudo-black hole. Energy generation is described by a kinematic viscosity law and a modified α-disk model. A disk with constant kinematic viscosity settles to a nearly steady stae which approximates a thin disk solution. Its unstable vertical distribution of entropy leads to mild subsonic correction. The α-disk is unstable, as expected, and collapses to a thin cold sheet with low accretion rate and low luminosity. Publication: The Astrophysical Journal Pub Date: December 1987 DOI: 10.1086/165859 Bibcode: 1987ApJ...323..634E Keywords: Accretion Disks; Black Holes (Astronomy); Galactic Radiation; Hydrodynamic Equations; Astronomical Models; Finite Difference Theory; Gravitational Collapse; Steady State; Astrophysics; BLACK HOLES; HYDRODYNAMICS; STARS: ACCRETION full text sources ADS |

Application of the time dependent finite difference theory to the study of sound and vibration interactions in ducts

The time dependent finite difference theory is extended to the solution of the acoustic wave equation in rectangular ducts when acoustic/structural interactions are allowed at a duct wall. The treatment of the boundary condition which describes the coupling is examined, and the stability of the procedure is studied and found to depend on the nature of this coupling. The convergence of solutions is discussed as a function of the discretization of the solution domain, particularly at frequencies approaching resonance.

A numerical study of nonspherical black hole accretion. II - Finite differencing and code calibration

view Abstract Citations (201) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A numerical study of nonspherical black hole accretion. II - Finite differencing and code calibration Hawley, J. F. ; Smarr, L. L. ; Wilson, J. R. Abstract A two-dimensional axisymmetric computer code for calculating fully relativistic ideal-gas hydrodynamics around a Kerr black hole is described. This code is being used to study fully dynamic inviscid-fluid accretion onto black holes, as well as the evolution and development of nonlinear instabilities in pressure-supported accretion disks. The numerical techniques are developed and discussed. A variety of alternate differencing schemes are compared on an analytic test bed. Some discussion is devoted to general issues in finite differencing. The working code is calibrated using analytically solvable accretion problems, including the radial accretion of dust and of fluid with pressure (Bondi accretion). Two-dimensional test problems include the spiraling infall of low-angular-momentum fluid, the formation of a pressure-supported torus, and the stable evolution of a torus. Publication: The Astrophysical Journal Supplement Series Pub Date: June 1984 DOI: 10.1086/190953 Bibcode: 1984ApJS...55..211H Keywords: Black Holes (Astronomy); Computational Fluid Dynamics; Finite Difference Theory; Gas Dynamics; Stellar Mass Accretion; Calibrating; Codes; Cosmic Dust; Hydrodynamic Equations; Inviscid Flow; Relativistic Effects; Shock Tubes; Astrophysics full text sources ADS |

Stable Galerkin Methods for Hyperbolic Systems

This paper considers the stability of the Galerkin method for first order hyperbolic systems. Just as in finite difference theory, many Galerkin methods, stable and convergent for the Cauchy problem, are unstable for hyperbolic boundary value problems because of improper treatment of the boundary conditions. The usual Galerkin method is seen to be unstable for a linear, constant coefficient, well-posed hyperbolic system on $[0,1]$ A method of treating boundary conditions is then proposed which will yield a stable and convergent method for any well-posed, linear, hyperbolic system in one dimension. This idea generalizes in a natural way to problems in more than one space dimension. Examples in one and two dimensions are considered. This paper extends the work of Gunzburger [Math. Comp., 31 (1977), pp. 671–675] to the general hyperbolic system.

Acoustics in variable area duct - Finite element and finite difference comparisons to experiment

Plane wave sound propagation without flow in a rectangular duct with a converging-diverging area variation is studied experimentally and theoretically. The area variation was of sufficient magnitude to produce large reflections and induce modal scattering. The rms pressure and phase angle on both the flat and curved surface were measured and tabulated. The steady-state finite element theory of Astley and Eversman and the transient finite difference theory of White are in good agreement with the data. It is concluded that numerical finite difference and finite element theories appear ideally suited for handling duct propagation problems which encounter large area variations. f* h * //* J k L* P p P0 S t U

A numerical study of the pitch-angle scattering of cosmic rays

view Abstract Citations (34) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A numerical study of the pitch-angle scattering of cosmic rays Kota, J. ; Merenyi, E. ; Jokipii, J. R. ; Kopriva, D. A. ; Gombosi, T. I. ; Owens, A. J. Abstract The results are presented of a careful study of finite-difference solutions to the problem of cosmic-ray transport, including pitch-angle scattering. In contrast to some recent studies, the diffusion approximation is confirmed in cases where the scattering mean free path is small compared with other length scales. The reasons for the discrepancy with the conclusions of Gombosi and Owens are discussed. Publication: The Astrophysical Journal Pub Date: March 1982 DOI: 10.1086/159744 Bibcode: 1982ApJ...254..398K Keywords: Cosmic Rays; Finite Difference Theory; Nuclear Scattering; Numerical Analysis; Particle Acceleration; Pitch (Inclination); Anisotropy; Diffusion Theory; Interstellar Magnetic Fields; Mean Free Path; Proton Flux Density; Solar Flares; Transport Theory; Space Radiation full text sources ADS |

Comparison of finite differences and finite elements in the case of a large fast power reactor

A large number of test calculations in two-dimensional hexagonal geometry for different configurations of SUPER-PHENIX 1 type Fast Reactor have been performed to compare finite difference theory vs finite element theory performances. At present, no definitive advantages were found for the application of the finite element method to two-dimensional hexagonal design calculations.

The seismic response of sediment-filled valleys. Part 1. The case of incidentSHwaves

abstractIn this study is presented the extension to time domain calculations of the Aki-Larner method (Aki and Larner, 1970), developed to investigate the scattering of plane waves at irregular interface. Seismograms computed at the surface of a soft basin for SH waves vertically incident are compared with results obtained by finite difference, finite element, and asymptotic ray theory methods. The method is then applied to a study of the seismic response of sediment-filled valleys to incident SH waves. Various geometries and rheological parameters are considered. The study shows the important role played by the nonplanar interface, which, when the incident wavelengths are comparable to the depth of the valley, results in the generation of Love waves which may have much larger amplitude than the disturbance associated with the direct incident signal. In the presence of a high-velocity contrast between the sediments and the underlying bedrock, these local surface waves can be reflected several times at the edges of the valley, resulting in a long duration of the ground shaking in the basin. In the case of a lower impedance contrast, these waves may produce disturbances on the outer sides of the valley.

The value of the mixing length

view Abstract Citations (36) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The value of the mixing length Deupree, R. G. ; Varner, T. M. Abstract The two-dimensional hydrodynamic calculations of Deupree are used, to derive an analytic fit for the ratio of the mixing length to pressure scale height. Although based on models with very shallow convective envelopes, this fit is assumed to be valid, with an arbitrary extension, to deeper convective envelopes. Stellar evolution sequences were calculated using the fit, and it was found that the fit (1) constrains the effective temperature at the Hayashi limit more than the range of tradition values for the mixing length and (2) is consistent with observations. Publication: The Astrophysical Journal Pub Date: April 1980 DOI: 10.1086/157900 Bibcode: 1980ApJ...237..558D Keywords: Convective Flow; Mixing Length Flow Theory; Scale Height; Stellar Envelopes; Stellar Evolution; Stellar Structure; Finite Difference Theory; Hydrodynamic Equations; Stellar Models; Stellar Temperature; Astrophysics full text sources ADS |

Three-dimensional dynamics of protostellar evolution

view Abstract Citations (41) References (12) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Three-dimensional dynamics of protostellar evolution. Cook, T. L. ; Harlow, F. H. Abstract A three-dimensional finite-difference numerical technique is outlined for self-gravitating rotating gaseous systems. The full nonlinear time-dependent equations describing a rotating self-gravitating fluid are solved in rotating cylindrical coordinates, and the time-dependent adiabatic collapse of gravitationally bound rotating protostellar clouds is analyzed for specified uniform and nonuniform initial conditions. It is found that uniform clouds can form axisymmetric rotating toroidal configurations, that nonuniform clouds can collapse to axisymmetric ellipsoids if the thermal pressure is high, and that the collapsing cloud is unstable to perturbations for low thermal pressures. The ensuing fragmentation of unstable protostellar clouds is examined by studying the response of self-gravitating equilibrium toroids to nonaxisymmetric perturbations. The results show that the detailed evolution of a fragmenting toroid depends on a nondimensional function of the initial entropy, as well as the total mass in the toroid, the rotational angular velocity, and the number of perturbation wavelengths around the circumference of the toroid. Publication: The Astrophysical Journal Pub Date: November 1978 DOI: 10.1086/156568 Bibcode: 1978ApJ...225.1005C Keywords: Finite Difference Theory; Protostars; Stellar Evolution; Stellar Models; Chandrasekhar Equation; Dynamic Models; Gravitational Collapse; Rotating Matter; Toroids; Astrophysics; Collapse:Protostellar Clouds; Hydrodynamics:Star Formation full text sources ADS |

Gas in globular clusters. II - Time-dependent flow models

view Abstract Citations (41) References (38) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Gas in globular clusters. II. Time-dependent flow models. Vandenberg, D. A. ; Faulkner, D. J. Abstract A numerical method is described for solving the time-dependent flow equations of relevance to gas flows in globular clusters. This method involves a modification of Henyey's iteration technique as well as finite-difference approximations for mass, momentum, and energy conservation. As an initial application of the numerical method, a previous study is extended to low gas-input energies in order to determine the fate of gas in clusters of one million solar masses when radiative cooling prevents the occurrence of steady-state outflows. Evolutionary sequences of models are presented for selected values of a parameter corresponding to the energy of the gas ejected by a star itself, and the resulting unsteady winds are shown to be similar to those computed by Mathews and Baker (1971) for elliptical galaxies. The results indicate that accumulation of mostly neutral hydrogen may take place in a region of small dimensions near the center of the most tightly bound globular clusters. Publication: The Astrophysical Journal Pub Date: December 1977 DOI: 10.1086/155695 Bibcode: 1977ApJ...218..415V Keywords: Astronomical Models; Gas Flow; Globular Clusters; Interstellar Gas; Stellar Mass Ejection; Time Dependence; Boundary Value Problems; Dynamic Models; Finite Difference Theory; Hydrodynamic Equations; Iterative Solution; Radiant Cooling; Astrophysics full text sources ADS |