Changes between Version 24 and Version 25 of u/erica/AccretionModelingBlog


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Timestamp:
03/20/18 20:25:28 (7 years ago)
Author:
Erica Kaminski
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  • u/erica/AccretionModelingBlog

    v24 v25  
    11== Bondi Accretion ==
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    3 Am working on a 3D simulation of Bondi Flow onto a central sink particle and studying the accretion properties using the Krumholz accretion algorithm. From Bondi (1952) we have the following quantities (in order: Bondi radius, accretion rate, sonic radius, nondimensional density and velocity):
     3Am working on a 3D simulation of Bondi Flow onto a central sink particle and studying the accretion properties using the Krumholz accretion algorithm. From Bondi (1952), we have the following quantities (in order: Bondi radius, accretion rate, sonic radius, nondimensional density and velocity):
    44
    55$R_{BH} = \frac{GM_*}{C_\infty^2}$
     
    5353|| $R_{s}$ || .0128 ||
    5454
    55 Note, the sonic radius is not resolved by ~ factor of 20 in this simulation, as seen when checking dx quoted above. The problem module for this sim sets of the Bondi solution everywhere in the grid at t=0 (except within a small inner radius, described below). In subsequent timesteps, the Bondi solution is re-pasted into the ghost zones and a small inner spherical region at the origin. A sink particle is initialized at the origin with mass given above ($M_{sink}=M_*$). The particle can accrete gas following the Krumholz prescription. The only source of gravity in the sims is the point gravity object associated with the particle (self-gravity is turned off).
     55Note, the sonic radius is not resolved by ~ factor of 20 in this simulation, as seen when checking dx quoted above. In this sim, the Bondi solution was initialized everywhere in the grid at t=0 (except within a small inner radius, described below). In subsequent timesteps, the Bondi solution is re-pasted into the ghost zones and a small inner spherical region at the origin. A sink particle is initialized at the origin with mass given above ($M_{sink}=M_*$). The particle can accrete gas following the Krumholz prescription. The only source of gravity in the sims is the point gravity object associated with the particle (self-gravity is turned off).
    5656
    5757The simulation setup reproduces the correct nondimensional profiles. Here's a comparison of the t=0 nondimensional density and velocity profiles astrobear calculates for the bondi module (left), compared to the Bondi solutions for $\gamma=5/3$ (curves II and III for the case of $\lambda=\lambda_{crit}$).