First common envelope trial runs

Recap of Last Post
The last post I had presented runs of an isolated RG that was quasi-stable after applying the damping prescription of Ohlmann+17, using the freefall timescale of s as the dynamical timescale.

New Work
This time I've tried the following:

  • Translating the star across the grid
  • Adding a secondary

Summary of New Results

  • Translating the star did not work because I was doing it incorrectly I now realize.
  • Adding the secondary seems to produce reasonable results, except I realize now that I forgot to initialize the primary with the required velocity.

Results

I) Isolated RG runs from last blog
Damp059) Periodic hydro BCs, Periodic Poisson BCs, ambient dyne/cm
(bluehive standard 120 cores up to 33 then bluestreak 8192 cores, 2 cpus/task)
( cm, , 4 levels AMR)
​2d density

  • Note: this has been extended in time since the last post, but I haven't used this run for the simulations presented below. Instead I've used run "Damp062" below with extrapolated hydro BCs and multipole expansion Poisson BCs.

Damp060) Extrapolated hydro BCs, Multipole expansion Poisson BCs, ambient dyne/cm
( cm, , 4 levels AMR)
(Damp060 stampede normal, about 2 days with 1024 cores, 1 cpu/task for half and then 512 cores, 1 cpu/task for half)
​2d density

Damp062) Extrapolated hydro BCs, Multipole expansion Poisson BCs, ambient dyne/cm
( cm, , 5 levels AMR)
(Bluehive standard 120 cores up to frame 7 and then about 2 days on comet compute 864 cores, 2 cpus/task up to frame 150 )
​2d density

II) Translating the RG across the grid

  • Two methods were tried: 1) add 30 km/s to every point; and 2) add 30 km/s to only those points that belong to the star, defined by a threshold density.

Damp064) Restarts Damp062 from s just after damping ends
(Bluehive standard 120 cores)
​2d density

  • Translating every point at once leads to a numerical instability and the code crashes

Damp067) Restarts Damp062 from s just after damping ends
(Bluehive standard 120 cores)
​2d density
​2d zoomed density

  • Translating only points with g/cm allows the code to run but results look unphysical. Also, code becomes unreasonable slow.

III) Adding a secondary

  • A secondary of mass Msun was added at binary separation Rsun, so just oustide the outer radius of the RG Rsun.
  • The secondary was given an initial tangential velocity of km/s for run Damp066, and km/s for run Damp068. The latter velocity should result in a circular orbit according to my analytical calculation.
  • The IACCRETE variable was specified to be "KRUMHOLZ_ACCRETION"
  • The softening length for the spline softening was specified to be the same as that used for the RG.

Damp066) Restarts Damp062 from s just after damping ends, km/s
(Bluehive standard 120 cores)
​2d density
​2d zoomed density

Damp068) Restarts Damp062 from s just after damping ends, km/s
(Comet compute 1728 cores, 2 cores/task)
​2d density
​2d zoomed density

Discussion and Next Steps

  • Translating the star needs to be done by giving a velocity to the central point mass and envelope only at the start.
  • When introducing the secondary, I forgot to give the primary an initial velocity. I will redo run Damp068 giving the primary the appropriate inital velocity.
  • At the same time I am working on improving the stability of the RG. I will be experimenting with buffer zones, which Baowei has shown me how to implement. The gain in efficiency should allow me to impose a higher max resolution.
  • Must put label "X" on particles…

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