Changes between Version 5 and Version 6 of u/lchamandy/2017-04-21


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Timestamp:
05/02/17 11:45:50 (8 years ago)
Author:
Luke
Comment:

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  • u/lchamandy/2017-04-21

    v5 v6  
    1 '''__Damping with AMR__'''\\
    2 '''a) Reflecting hydro BCs, Multipole expansion Poisson BCs, $\tau=10^5$ s (Damp044)'''\\
     1__Introduction__\\
     2The last blog post I was struggling to avoid a cubical ("boxy") and thus unstable star. This boxiness is worse with AMR but reduces with damping.
     3However, we cannot keep damping turned on indefinitely. I had found that changing the BCs can make a difference.
     4It occurred to me that using periodic BCs may avoid this problem. Periodic BCs were used by Ohlmann+17.
     5I experimented again with different BCs in Sections I and II.
     6
     7In Section II below I vary the value of the damping time scale $\tau$ according to the prescription of Ohlmann+17,
     8using the free-fall time $3\times10^5$ s as the dynamical timescale $t_\mathrm{dyn}$,
     9rather than the more conservative sound-crossing time of $7.5\times10^5$.
     10Here $\tau$ is ramped up to $\infty$ over $5t_\mathrm{dyn}$, and then left undamped for another $5t_\mathrm{dyn}$.
     11In Section III I try a run that includes AMR and the Ohlmann damping prescription (still running).
     12
     13__Results__\\
     14- For the small-box simulations without AMR of Section II below, the periodic/periodic hydro/Poisson BCs seem to help to keep the star spherical,
     15though they increase the computation time by a factor of a few compared to extrapolating/multipole expansion BCs.
     16
     17- For AMR and a twice larger box, the BCs seem to matter much less (see comparison of Ib and If below).
     18
     19- It dawned on me that maybe the ambient pressure is just too high at $10^7$ dyne/cm$^2$, and that this leads to boxiness. This value had led to a more stable star than $10^6$ dyne/cm$^2$ in the small-box low res uniform grid sims. But with AMR we can still resolve the outer scale height if the ambient pressure is $10^6$.
     20
     21- So I did some runs with $10^6$ dyne/cm$^2$, and the results were encouraging. Not only is the star more spherical, but the computation time is typically reduced by a factor of a few.
     22
     23- The star is still not perfectly spherical nor perfectly stable for the $10^6$ dyne/cm$^2$ runs below, but clearly reducing the ambient pressure is the correct thing to do.
     24
     25__Next steps__\\
     26- Run III(a) is ongoing. In the meantime, it will be worth doing the same run but with Extrapolating/multipole expansion BCs, which should be faster. If the results are similar, I will stick with the Extrapolating/multipole expansion, which are probably more physical than periodic/periodic and reduce the computation time.
     27
     28- Simultaneously I will try the same run but with ambient pressure reduced to $10^5$ dyne/cm$^2$ and $3\times10^5$ dyne/cm$^2$ to see if further improvements can be made. Clearly the pressure must be as low as possibly while still adequately resolving the scale height at the surface.
     29
     30- Then it would be worth increasing the box size and resolution to be more comparable with those of Ohlmann+17. At this point we would have to make a final choice for the ambient pressure and dynamical time scale.
     31
     32- After this, if everything looks good, we need to test the stability of the star as it translates along the grid. Finally we can introduce the secondary (point particle).
     33
     34'''__I) Damping with AMR__'''\\
     35'''a) Reflecting hydro BCs, Multipole expansion Poisson BCs, $\tau=10^5$ s, ambient $P=10^7$ dyne/cm$^2$  (Damp044)'''\\
    336[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp044/rho2d_Damp044.gif 2d density]
    437[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp044/rho2dv1e6_Damp044.gif 2d density and velocity]\\
    538
    6 '''b) Extrapolating hydro BCs, Multipole expansion Poisson BCs, $\tau=10^5$ s (Damp047)'''\\
     39'''b) Extrapolating hydro BCs, Multipole expansion Poisson BCs, $\tau=10^5$ s, ambient $P=10^7$ dyne/cm$^2$  (Damp047 27 hrs on comet compute 576 cores)'''\\
    740[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp047/rho2d_Damp047.gif 2d density]
    841[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp047/rho2dv1e6_Damp047.gif 2d density and velocity]\\
    942
    10 '''c) Extrapolating hydro BCs, Multipole expansion Poisson BCs, $\tau=10^4$ s (Damp049)'''\\
     43'''c) Extrapolating hydro BCs, Multipole expansion Poisson BCs, $\tau=10^4$ s, ambient $P=10^7$ dyne/cm$^2$ (Damp049)'''\\
    1144[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp049/rho2d_Damp049.gif 2d density]
    1245[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp049/rho2dv1e6_Damp049.gif 2d density and velocity]\\
    1346
    14 '''d) Extrapolating hydro BCs, Multipole expansion Poisson BCs, $\tau=3\times10^4$ s (Damp050 running on comet)'''\\
     47'''d) Extrapolating hydro BCs, Multipole expansion Poisson BCs, $\tau=3\times10^4$ s, ambient $P=10^7$ dyne/cm$^2$  (Damp050 run on comet)'''\\
    1548[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp050/rho2d_Damp050.gif 2d density]
    1649[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp050/rho2dv1e6_Damp050.gif 2d density and velocity]\\
     50
     51'''e) Extrapolating hydro BCs, Multipole expansion Poisson BCs, $\tau=1\times10^5$ s, ambient $P=10^6$ dyne/cm$^2$  (Damp058 run on comet)'''\\
     52[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp058/rho2d_Damp058.gif 2d density]
     53[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp058/rho2dv1e6_Damp058.gif 2d density and velocity]\\
     54
     55'''f) Periodic hydro BCs, Periodic Poisson BCs, $\tau=1\times10^5$ s, ambient $P=10^7$ dyne/cm$^2$  (Damp057 22 hrs on stampede normal 512 cores)'''\\
     56[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp057/rho2d_Damp057.gif 2d density]
     57[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp057/rho2dv1e6_Damp057.gif 2d density and velocity]\\
    1758
    1859'''Comparison with (a) on left and (b) on right'''\\
    … …  
    2061[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/rho2dv1e6_reflec_extrap_amr 2d density and velocity]\\
    2162
    22 '''Comparison with (b) on left and (c) on right'''\\
    23 [http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/rho2d_tau1e5_1e4_amr 2d density]
    24 [http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/rho2dv1e6_tau1e5_1e4_amr 2d density and velocity]\\
     63'''Comparison with (b) on left and (f) on right'''\\
     64[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/rho2d_reflec_extrap_amr 2d density]
     65[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/rho2dv1e6_reflec_extrap_amr 2d density and velocity]\\
    2566
    26 '''__Damping with evolving tau__'''\\
     67'''__II) Damping with evolving tau__'''\\
    2768- Damping prescription as in Ohlmann+17, using $t_{dyn}=3\times10^5$s (about equal to the freefall time, while the sound-crossing time is about $7.5\times10^5$s).
    2869
    29 '''Reflecting hydro BCs, Multipole expansion Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp051)'''\\
     70'''a) Reflecting hydro BCs, Multipole expansion Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp051)'''\\
    3071[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp051/rho2d_Damp051.gif 2d density]
    3172[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp051/rho2dv1e6_Damp051.gif 2d density and velocity]\\
    3273
    33 '''Extrapolating hydro BCs, Multipole expansion Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp052 9 hrs on bluehive standard)'''\\
     74'''b) Extrapolating hydro BCs, Multipole expansion Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp052 9 hrs on bluehive standard 120 cores)'''\\
    3475[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp052/rho2d_Damp052.gif 2d density]
    3576[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp052/rho2dv1e6_Damp052.gif 2d density and velocity]\\
    3677
    37 '''Extrapolating hydro BCs, Periodic Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp053 8 hrs on bluehive standard)'''\\
     78'''c) Extrapolating hydro BCs, Periodic Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp053 8 hrs on bluehive standard 120 cores)'''\\
    3879[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp053/rho2d_Damp053.gif 2d density]
    3980[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp053/rho2dv1e6_Damp053.gif 2d density and velocity]\\
    4081
    41 '''Periodic hydro BCs, Periodic Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp054 33 hrs on bluehive standard)'''\\
     82'''d) Periodic hydro BCs, Periodic Poisson BCs, ambient $P=10^7$ dyne/cm$^2$ (Damp054 33 hrs on bluehive standard 120 cores)'''\\
    4283[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp054/rho2d_Damp054.gif 2d density]
    4384[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp054/rho2dv1e6_Damp054.gif 2d density and velocity]\\
    4485
    45 '''Extrapolating hydro BCs, Multipole expansion Poisson BCs, ambient $P=10^6$ dyne/cm$^2$ (Damp055 4 hrs on bluehive standard)'''\\
     86'''e) Extrapolating hydro BCs, Multipole expansion Poisson BCs, ambient $P=10^6$ dyne/cm$^2$ (Damp055 4 hrs on bluehive standard 120 cores)'''\\
    4687[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp055/rho2d_Damp055.gif 2d density]
    4788[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp055/rho2dv1e6_Damp055.gif 2d density and velocity]\\
    4889
    49 '''Periodic hydro BCs, Periodic Poisson BCs, ambient $P=10^6$ dyne/cm$^2$ (Damp056 10 hrs on bluehive standard)'''\\
     90'''f) Periodic hydro BCs, Periodic Poisson BCs, ambient $P=10^6$ dyne/cm$^2$ (Damp056 10 hrs on bluehive standard 120 cores)'''\\
    5091[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp056/rho2d_Damp056.gif 2d density]
    5192[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp056/rho2dv1e6_Damp056.gif 2d density and velocity]\\
     93
     94'''__III) Damping with AMR and evolving tau__'''\\
     95'''a) Periodic hydro BCs, Periodic Poisson BCs, ambient $P=10^6$ dyne/cm$^2$ (Damp059 bluehive standard 120 cores up to 33 then bluestreak 8192 cores)'''\\
     96[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp059/rho2d_Damp059.gif 2d density]
     97[http://www.pas.rochester.edu/~lchamandy/Graphics/RGB/Post-sink_particle/Post-modified_Lane_Emden/Damp059/rho2dv1e6_Damp059.gif 2d density and velocity]\\