Numerical Simulation of Instability in Wind Accretion Flow

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We considered a close binary system consisted by a compact object, such as a black hole, a neutron star or a white dwarf, and a companion star, such as a giant or a main sequence star. And we performed numerical simulations of accretion flows in it. There are two types of accretion flows, i.e. a wind accretion flow and an accretion disc. We considered both cases.As to wind accretion, I cooperated with E.Shima at Kawasaki Heavy Industries, U.Anzer and G.Boerner at Max-Planck Institute and H.Boffin at Cardiff University. We assume that the flow is restricted within a region of constant thickness and also gas to be isothermal. We found that the flow was very unstable and that the accretion column waved like a snake. This is contrary to the criticism posed by Swiss researchers to our earlier works.The flow is nearly steady at first and forms a very long accretion column behind the compact object. When we continue the calculation long enough, the column begins to wave and the amplitude grows with time. Occasionally an accretion disc is formed about the object.We also performed number of numerical simulations of relating matters, such as three dimensional accretion disc, the interaction between the solar wind and an interstellar matter, and explosion of a supernova.