Update 12/31: Common Envelope Wind Tunnel Run 003

Finished Run

WT Run 003

  • Gamma fixed to 5/3, AMR enabled. Order of 2 larger box.
  • Setup: 3Msun AGB + 0.1Msun secondary. 1012cm separation.
  1. Particle mass: 1.989e32 g
  2. Wind temperature: 5.56862e5 K
  3. Wind density: 0.0001 g/cm3
  4. Particle radius: 8.364e9 cm = 1.0 CU = 0.120 Rsun
  5. Bondi radius: 1.564e11 cm = 18.7 CU = 2.249 Rsun
  6. Run Time: 2 TS = 2 wind passing time of the box = 8.68e5 s ~ 10 days
  • Sim parameters:
  1. Box size 5123 CU
  2. Base grid res.: 1283, max res. 10243.
  3. Time Scale = 4.34e5s.
  4. Length Scale: 1 CU = 8.364e9 cm = 0.120 Rsun
  5. Time Resolution: 0.01CU = 4.34e3s
  6. Accretion = none.
  7. BC: extrapolated
  8. Gamma: 1.67
  9. Softening length: 10CU (20 pixels)
  10. Run time: ~ 2 days

Preliminary Results

​ Log density movie ​ Mach number movie ​ total energy (E + U) movie

  • Cylinerical symmetry preserved thanks to larger softening length.
  • Particle accelerates away from the (front) bow shock.
  • No Krumholtz accretion. Particle mass stays constant.
  • (Near) sperical region where the gas is bounded by the particle, i.e. E_int + E_kinetic<|U|, as marked by the blue line in the third movie.

I then extracted the acceleration of the particle, comparing it to the HL Rate:

The blue dashed line marks the moment when the bow shock behind (+x direction) the particle reaches the right boundary. Currently computing dynamic friction by integrating the gravity of the gas within spherical regions of 1, 2, and 4 Bondi radii, as well as that of the gravitationally bounded gas.

Although Krumholtz accretion routine did not pick up any mass, I integrated sperical regions again of 1, 2, and 4 Bondi radii, as well as the gravitationally bounded gas, to characterize the clustering of gas around the point particle. http://www.pas.rochester.edu/~bpeng6/WindTunnelTest/NEW/Run003/MassEnc.png

The dotted line is the prediction of H-L accretion. Mass enclosed in all four regions all start off growing roughly linearly, before reaching a equilibrium. This can be related to the sink particle not working properly and causing a pressure buildup witin the softening radius.

The accretion rate, as normalized by the H-L rate, is shown below.

http://www.pas.rochester.edu/~bpeng6/WindTunnelTest/NEW/Run003/AccRate.png

Next Steps

  • Higher resolution and smaller softening radius (preferably have it equal to the physical radius of the secondary star), hopefully get the Krumholtz accretion functional.
  • Shorter run time: seems when the bow shock reaches the boundary, the boundary conditions are changed, which may be related to the stagnant accretion & dynamic friction.
  • Given shorter run time, may have higher time resolution.

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