The work developed in this thesis addresses very important and relevant issues of accretion processes around black holes. Beginning by studying the time variation of the evolution of inviscid accretion discs around black holes, and their properties, the author investigates the change of the pattern of the flows when the strength of the shear viscosity is varied and cooling is introduced. He succeeds to verify theoretical predictions of the so called Two Component Advective Flow (TCAF) solution of the accretion problem onto black holes through numerical simulations under different input parameters. TCAF solutions are found to be stable. And thus explanations of spectral and timing properties (including Quasi-Period Oscillations, QPOs) of galactic and extra-galactic black holes based on shocked TCAF models appear to have a firm foundation.

Auteur
Dr. Kinsuk Giri performed his research for his PhD thesis at S.N. Bose National Research Centre for Basic Sciences in Kolkata, India, under supervision of Prof. S.K. Chakrabarti. He was awarded his PhD from Jadavpur University in 2013. Afterwards he took up a postdoc position at the Institute of Astronomy, National Tsing Hua University Hsinchu, Taiwan.

Contenu
Introduction.- Overview of Numerical Simulations on Accretion Processes and Our Objectives.- Governing Equations and Computational Methods.- Simulation Procedure and the Test of the Code.- Simulation for Inviscid Sub-Keplerian Flows and Shocks.- Simulation of Viscous Accretion Flows.- Effects of Power-law Cooling in Viscous Flows.- Conclusions and Future Plans.