GALLERY

  • An m=2 mode grows in a self-gravatating disk. Density waves propagate outwards. The color scale shows the density of the disk.
  • A grayscale of the vorticity in an accretion disk shows anticyclonic vortices (in dark) interacting and merging together (from an initially random perturbation of the vorticity field).
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  • A color scale of the vorticity shows a vortex in a protostellar disc. The disc is a 2D polytropic model. The matter in the vortex is rotating clock wise, while the matter in the disc and the vortex itself are rotating counter clockwise. Perturbations (see below) of the density and velocities decay in the disc, but vortices can be present for longer periods of time.
  • A grey scale of the density is shown. A double spiral shock waves is induced in an accretion disc due to the tidal force of a companion of small mass located to the right.
  • An monochromatic (orange) scale of the density. A disc perturbed by a random-like noise in the velocity, evolves into sheared spiral pattern (t=2 orbits). The disc is hydrodynamically stable to non-linear perturbation, and after several hundreds of inner radius orbits, the waves dissipate and/or exit the boundaries.
  • A salmon scale of the density. The same disc (as above) is shown after some 10 orbits. The small scale perturbation have been dissipated due to the inverse cascade of energy, typical of 2D flows, that transfers the energy contained in the small scales to the larger scales. Eventually an eccentric (m=1) mode dominates the disc.
  • A color scale of the density is shown in the inner region of an accretion disc. A non-axisymmetric instability (the Papaloizou-Pringle instability) develops in the disc when the inner boundary is reflective. When the viscosity is very low the instability evolves into turbulence (shown in the picture) confined in the innermost part of the disc.

    DEEP IMPACT !

    The northern hemisphere of the earth is shown in this color scale of the density. The North Pole is marked by a tiny dark spot in the middle of the figure. A meteorite has impact the earth at 50 degree north and a shock waves propagates outwards. For more see Deep Impact !
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