Changes between Version 24 and Version 25 of u/BonnorEbertMatched2
 Timestamp:
 10/15/12 22:04:55 (12 years ago)
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u/BonnorEbertMatched2
v24 v25 46 46 '''Stability''' 47 47 48 Stability test of the critical BE sphere placed in an ambient rho=0.01rho(Rbe), with sphere and ambient in pressure equilibrium at r=Rbe. This is just the B&P sphere, with no density enhancement, in a box twice as large. My apologies, but the movie is broken into 2, with the first half here: https://clover.pas.rochester.edu/trac/astrobear/attachment/wiki/u/BonnorEbertMatched/rhoCroppedLight.gif and second half here: https://clover.pas.rochester.edu/trac/astrobear/attachment/wiki/u/BEmoviesLonger/rhoSecondHalf.gif. This setup was stable to collapse for at least 5 crossing times, where 1 tc= 0.2 in computational units, as can be seen from this 2d slicethrough the center of the sphere. Here the sphere is breathing about its equilibrium initial condition.48 Stability test of the critical BE sphere placed in an ambient rho=0.01rho(Rbe), with sphere and ambient in pressure equilibrium at r=Rbe. This is just the B&P sphere, with no density enhancement, in a box twice as large. This setup was stable to collapse for 5 crossing times, where tc= 0.2 in computational units, as can be seen from this lineout of rho through the center of the sphere. Here the sphere is breathing about its equilibrium initial condition. 49 49 50 50 [[Image(rhoLight.png, 20%)]] … … 54 54 '''B&P, classic outsidein collapse''' 55 55 56 'Classic B&P collapse' of a BE sphere. That is, 10% density enhancement of sphere above equilibrium values, in pressure equilibrium with a light (rho=0.01rho(Rbe) ) ambient. Th is, as well as the following plots, show lineouts through the center of the sphere of the quantities: rho, absolute value(radial velocity), absolute value(mach), and pressure, all normalized to their initial values in the grid. The xaxis is logarithmic and begins at the length of the smallest zone dx. The yaxis is linear: http://www.pas.rochester.edu/~erica/BPJuly22.gif. The collapse here resembles the B&P results, namely collapse proceeds in an outsidein fashion and remains subsonic most of the way through.56 'Classic B&P collapse' of a BE sphere. That is, 10% density enhancement of sphere above equilibrium values, in pressure equilibrium with a light (rho=0.01rho(Rbe) ) ambient. These are lineouts through the center of the sphere of the quantities: rho, abs(radial velocity), abs(mach), and pressure, all normalized to their initial values in the grid. The xaxis is logarithmic and begins at the length of the smallest zone dx. The yaxis is linear. The collapse here resembles the B&P results, namely collapse proceeds in an outsidein fashion and remains subsonic most of the way through. 57 57 58 58 [[Image(BPrho.png, 20%)]] … … 64 64 65 65 66 BE sphere in an ambient rho= rho(Rbe). This is the same setup as above, except now there is no 10% rho enhancement and the ambient has same density as BE sphere at r=Rbe. http://www.pas.rochester.edu/~erica/MatchedJuly26.gif Here collapse seems to be proceeding in a very different manner. At small times, material begins to pile up at the sphere's outer edge. After enough material has accumulated, the pressure at the sphere's outer edge exceeds critical values and moves inward with time in a compression wave. The collapse is supersonic most of the way through. Note, radial velocity is now the actual quantity, to show clearly the sign (<0 is moving inward, >0 is moving outward).66 BE sphere in an ambient rho= rho(Rbe). This is the same setup as above, except now there is no 10% rho enhancement and the ambient has same density as BE sphere at r=Rbe. Here collapse seems to be proceeding in a very different manner. At small times, material begins to pile up at r=Rbe. After a small fraction of material has accumulated, the pressure at r=Rbe exceeds critical values and moves inward with time in a compression wave. The collapse is supersonic most of the way through. Note, radial velocity is now the actual quantity, to show clearly the sign (<0 is moving inward, >0 is moving outward). 67 67 68 68 [[Image(rhoMatched.png, 20%)]] … … 84 84 85 85 86 In summary, I would say that the runs in which collapse was NOT induced to occur through a density enhancement, seem to proceed much differently. They resembled qualitatively the runs by Hannebelle et al., in which a pressure wave moved through the sphere, causing collapse into a sink particle. The resolution of these sims became poor by the time the apparent wave has moved into the sphere, so the simulation was killed ostensibly before a sink formed. I can run these simulations out longer and at higher resolution as a next step if you suggest. This however, will be postponed until after I take the preliminary PhD written exam, due to take place at the end of August.86 In summary, I would say that the runs in which collapse was NOT induced to occur through a density enhancement, seem to proceed much differently. They resembled qualitatively the runs by Hannebelle et al., in which a pressure wave moved through the sphere, causing collapse into a sink particle. The resolution of these sims became poor by the time the apparent wave has moved into the sphere, so the simulation was killed ostensibly before a sink formed. I can run these simulations out longer and at higher resolution as a next step if you suggest.