Changes between Version 41 and Version 42 of u/erica/AccretionModelingBlog
- Timestamp:
- 04/20/18 12:00:49 (7 years ago)
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u/erica/AccretionModelingBlog
v41 v42 1 = = Bondi Accretion ==1 = Bondi Accretion = 2 2 3 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 [http://adsabs.harvard.edu/abs/1952MNRAS.112..195B Bondi (1952)], we have the following quantities (in order: Bondi radius, accretion rate, sonic radius, nondimensional density and velocity): … … 30 30 Note, the sink dx is equivalent to the accretion volume radius ($r_{acc}$). 31 31 32 = = Research Log: ==32 = Research Log: = 33 33 34 === 3/18/18, $\gamma=7/5$ case=== 34 = 4/19/18 = 35 36 === $\gamma=1.4$ === 37 38 Ran 3 more tests for the case of $\gamma=1.4$ Bondi flow: 1) decreasing the timestep to better observe the evolution of the gas in the kernel as it becomes an outflow into the grid, 2) instead of starting with the Bondi flow in the ambient medium, start with a uniformly dense ambient medium and see if it evolves into the Bondi flow given the accretion routine, 3) hard code the mdot into the sink particle's accretion rate as a sanity check that the particle/gas is behaving as expected. 39 40 ==== Smaller dt ==== 41 42 ==== Uniform Ambient Medium ==== 43 44 ==== Hard Coded Mdot ==== 45 46 === $\gamma=1.0001$ === 47 48 Next checked whether a smaller gamma still produces a supersonic backwind into the grid from the kernel. To do this, kept the same relative resolution between the kernel and the sonic radii. For $\gamma=1$, $R_s=21$, as opposed to $R_s=6$ for $\gamma=1.4$ flow. 49 50 = 3/18/18, $\gamma=7/5$ case = 35 51 36 52 Am running the $\gamma=7/5$ case because the sonic point in this case is located far beyond the accretion radius ($R_s=6>>R_{acc}=.625$). This will enable us to see the generation of accretion shocks in the sim and check the behavior of the accretion algorithm under conditions of supersonic infall. We expect that the accretion algorithm should be fairly 'well-behaved' in the supersonic regime, as any pressure errors generated in the accretion kernel will be unable to propagate upstream and effect the hydrodynamical solution beyond the accretion volume. … … 101 117 102 118 103 = == 3/18/18, $\gamma=1.66$, steady-state case ===119 = 3/18/18, $\gamma=1.66$, steady-state case = 104 120 105 121 The case of $\gamma=5/3$ flow is an extreme limit for the solution space. This value of $\gamma$ has a few interesting features:
