Changes between Version 21 and Version 22 of u/erica/AccretionModelingBlog


Ignore:
Timestamp:
03/20/18 20:20:54 (7 years ago)
Author:
Erica Kaminski
Comment:

Legend:

Unmodified
Added
Removed
Modified
  • u/erica/AccretionModelingBlog

    v21 v22  
    4747In other words, when $\gamma=5/3$ exactly, we have no accretion flow.
    4848
    49 In addition to the Bondi/flow params cited in the top section of this page, the sim was setup using the following (in CU):
     49In addition to the Bondi/flow params cited in the top section of this page, the sim was set up using the following (in CU):
    5050
    5151|| $\gamma$ || 1.66 ||
     
    5353|| $R_{s}$ || .0128 ||
    5454
    55 Note, the sonic radius is not resolved by about a factor of 20 in this simulation, as seen when checking dx quoted above.
     55Note, 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).
    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 $\lambda=\lambda_{crit}$).
     
    6161The profiles are cut-off within an inner radius of $r=.875$ to avoid extremely high speeds there (am going to get rid of this in the next round of sims). Sampling the mass flux across a spherical shell less than this radius doesn't match up with the theoretical prediction of $\dot{M}=2692$ since the solution is getting stepped on there. Sampling the mass flux across a shell larger than this, however, produces agreement (2689 compared to 2692). 
    6262
    63 Since the solution is getting stepped on within some small inner radius, can't meaningfully check the behavior of the accretion algorithm and any spurious waves it might be generating there. Instead, will be removing this inner boundary in the next run. Would like to test the effect of the sonic radius being outside of the accretion radius as opposed to within. To test this will do a resolution study on $\gamma=7/5$ flow, where the sonic point is $~.2R_{BH}$.
     63Since the solution is getting stepped on within some small inner radius, can't meaningfully check the behavior of the accretion algorithm and any spurious waves it might be generating there. Instead, will be removing this inner boundary in the next run. These next sims will then be able to test the effect of the sonic radius being inside the accretion radius as opposed to outside. To test this will do a resolution study on $\gamma=7/5$ flow, where the sonic point is $\sim .2R_{BH}$.
    6464
    65 As the following images show, this set of ICs produces a steady-state solution.. This is due to the solution being stepped on within the accretion volume, which would likely be the first place any deviation from the similarity solutions would occur due to spurious pressure waves that the accretion algorithm might produce in such strongly subsonic flow such as this. The attached module files that produce these files are thus called "*_steadystate*"
     65As the following images show, this set of ICs produces a steady-state solution.. This is due to the solution being stepped on within the accretion volume, which would likely be the first place any deviation from the similarity solutions would occur due to spurious pressure waves that the accretion algorithm might produce in such strongly subsonic flow as this. The attached module files that produce these files are thus called "*_steadystate*"
    6666
    6767|| Mesh || [[Image(mesh_comparison.png, 15%)]] ||