Posts by author Bo Peng

CE Wind Tunnel: Update 09/27/17

Finished Run

WT Run 001

  • Previously overestimated temperature fixed.
  • Setup: 3Msun AGB + 0.1Msun secondary. 10e12cm separation. (Henceforth 3_-1_12)
    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: 1.564 cm = 18.7 CU = 2.249 Rsun
    6. Run Time: 2 TS = 2 wind passing time of the box = 3.472e5 s ~ 4 days
  • Sim parameters：
    1. Fix grid 2003.
    2. Time Scale = 1.736e5 s.
    3. Length scale: 1 CU = 8.364e9 cm = 0.120 Rsun
    4. Length resolution:: 1 CU
    5. Time resolution : 0.02 CU = 3.472e3 s
    6. Accretion = off.
    7. BC: extrapolated.
    8. Gamma = 1
    9. Softening length = 4 CU = 3.346e10 cm = 0.481 Rsun
    10. Run time: 00:56:13

Preliminary Results

http://www.pas.rochester.edu/~bpeng6/WindTunnelTest/NEW/logRhovVecRun001.gif

http://www.pas.rochester.edu/~bpeng6/WindTunnelTest/NEW/vxvVecRun001.gif

  • Clearly defined shock wave.
  • Significant accretion, density instability normal to the wind.
  • Significant movement of the particle, drag force overwhelms box effect.
  • ~ 80 CU displacement in 2 TS - let's end this sim here before the particle escapes the box.

Ongoing run

Test run for higher gamma: WT Heat Up 002

  • Setup: 3_-1_12 Run time = 1 TS No Particle Placed
  • Sim parameters：
    1. Fix grid 2003.
    2. Time Scale = 1.736e5 s.
    3. Length scale: 1 CU = 8.364e9 cm = 0.120 Rsun
    4. Length resolution:: 1 CU
    5. Time resolution : 0.01 CU = 1.736e3 s
    6. Accretion = off.
    7. BC: extrapolated.
    8. Gamma = 1.2
    9. Softening length = 4 CU = 3.346e10 cm = 0.481 Rsun

Next steps

  • More complete drag force & accretion analysis on its way.
  • Higher time resolution, shorter timescale.
  • Mesh refinement around the particle. Longer box.
  • Different gamma numbers.
  • Reconsider possibilities of periodic boundary conditions, fixed particle position. Or fixing the particle in place and measure accretion rate, then let go and measure drag.
  • Larger softening length?
  • Miscellaneous improvements for visualization.

Questions

  • Monday Luke mentioned extracting information on the fly, wonder how that works?
  • Sink particle radius defined as integer, which limits lowest resolution.
  • Force low resolution on the rim of the box to save time?
  • What's the optimal number of nodes & CPU per nodes to use?
  • Luke's method of measuring accretion rate & drag - comparable?