The formation of interstellar jets by convergence of supersonic conical flows and the further dynamical evolution of these jets are investigated theoretically by means of numerical simulations. The results are presented in extensive graphs and characterized in detail. Strong radiative cooling is shown to result in jets with Mach numbers 2.5-29 propagating to lengths 50-100 times their original widths, with condensation of swept-up interstellar matter at Mach 5 or greater. The characteristics of so-called molecular outflows are well reproduced by the simulations of low-Mach-number and quasi-adiabatic jets. 1988A&A...202..256T

The formation and stability of a Blandford-Rees (BR) twin exhaust jet (as observed in quasars, radio galaxies, and SS 433) is investigated, and a formula for relating jet luminosity to the internal energy of the confining cloud is developed. A de Laval nozzle is found to form hydrodynamically in a flat bottomed gravitational potential, remaining globally stable over a luminosity range of about 40, for a fixed confining gas pressure. Global Rayleigh-Taylor instability is observed, limiting the formation of high-luminosity jets, with instability to finite-amplitude Kelvin-Helmholtz (KH) pinching off KH molecules, rather than destroying nozzle structure. Hydrodynamic calculations to determine if the jet can form and remain stable are compared with steady state analytical work of BR (1974) and dynamical calculations of the jet boundary by Wiita (1978). 1981ApJ...247...52N

We present non-adiabatic hydrodynamic simulations of a supersonic light jet propagating into a fully ionized medium of uniform density on a scale representative of the narrow-line region (NLR) in Seyfert galaxies with associated radio jets. In this regime the cooling distance of the swept-up gas in the bowshock of the jet is of the same order as the transverse extent of the jet bowshock, as opposed to the more extreme regimes found for more powerful adiabatic large-scale jets or the slow galactic jets which have previously been simulated. We calculate the emissivity for the Halpha line and for radio synchrotron emission. We find that the structure of the line-emitting cold envelope of the jet cocoon is strongly dependent on the non-stationary dynamics of the jet head as it propagates through the ambient medium. We observe the formation of cloud-like high density regions which we associate with NLR clouds and filaments.1997MNRAS.286.1032S

• I - The hydrodynamic algorithms and tests.
• II - The magnetohydrodynamic algorithms and tests
• III - The radiation hydrodynamic algorithms and tests

I,II - 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.1992ApJS...80..753S, 1992ApJS...80..791S

III - 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 1992ApJS...80..819S

see also: ZEUS MHD 1989ApJ...342..700C

We investigate the physical behaviour in the nonlinear regime of Kevin-Helmholtz (KH) instabilities in a simple conducting shear flow in the presence of magnetic fields, based upon the use of numerical simulations of the ideal magnetofluid euqations of motion in two dimensions. The flow is characterized by three principal control parameters: the Mach number M of the shear flow, the ration a of the Alfven speed to the sound speed, and the effective diffusivity; we investigate how these parameters affect the evolution and saturation of the instability. 1996ApJ...456..708M (for full greyscale postscript version see Malagoli etal. (1995))

Two-dimensional simulations of the nonlinear evolution of unstable sheared magnetohydrodynamic flows. see density and Magnetic Pressure color image gallery , scanned article: 1996ApJ...460..777F

Radiative Shocks perturbed from steady state are subject to an oscillatory overstability. We have examined the nature of this overstability in one and two dimensions using numerical hydrodynamic simulations. We find that one-dimensional simulations of a uniform flow incident upon a reflecting wall produce oscialltion frequencies in agreement with those of Imamura, Wolff, & Durisen (1984, A numerical study of the stability of radiative shocks ) Simulations of 2D steady state shock reveals that transcerse pertubations in the shock front quickly manifest themselves in the cold, dense gas layers downstream. Pertubations of the cold gas layer are dominated by spatial wavelengths l<L , the cooling length of the shock. The action of this instability ensures that interstellar radiative shocks will not be smooth on length scales<L.1995ApJ...449..727S

The results of numerical simulation of mass transfer in semidetached non-magnetic binaries are presented. We investigate the morphology of gaseous flows on the basis of three-dimensional gas-dynamical calculations of interacting binaries of different types (cataclysmic variables and low-mass X-ray binaries). We find that taking into account a circumbinary envelope leads to significant changes in the stream-disc morphology. 1998MNRAS.300...39B

Two-dimensional hydrodynamic calculations of gas flow in a semidetached close binary system with mass ratio of unity are performed, solving the Euler equation using the second order Osher scheme in a multibox type of grid which provides a high resolution about a mass-accreting compact object. Results suggest that the tidal effect by the mass-losing star is significant, and that the gas particles lose their angular momentum at the shocks and can spiral in without the help of turbulent velocity. These results challenge fundamental assumptions of the standard disk model including an axisymmetric thin disk and the important role of turbulent velocity 1987MNRAS.224..307S

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