Posts in category Disks

Accretion Disk Update

I have been working on simulating an accretion disk embedded in the center of an AGB star. Previous simulations have utilized a sink particle that relieved thermal energy and led to very high accretion rates. Our sink particle is set to “NOACCRETION ”.

The box size is 10e11 cm

Accretion disk has Radius of 2*10e10 cm and Height of 5*10e9 cm

Animations of the density (Top Down):

https://guidarellig.github.io/RhoTop.mpg

and Temperature (Side):

https://guidarellig.github.io/TempSide.mpg

My first attempt to look at the accretion rate was to define a momentum flux with:

p = rho*v

dQ = p dot dA

Summing dQ over a surface yields the flow rate through that surface, I did this with spheres. The next animation shows the accretion rate in solar masses per year (y-axis) through spheres of different radii (x-axis) over time <note: positive value correspond to outward flow>:

https://guidarellig.github.io/AccretionZoomed.mpg

For a general sense of the direction of flow this animation shows red as outward flow and blue as inward:

https://guidarellig.github.io/Check.mpg

To represent accretion clearly Luke and Eric suggested calculating the total mass as a function of time. (it is much better)

The total mass inside a sphere of radius 0.4e10 cm:

https://guidarellig.github.io/MassInsideSpherep4R.png

Mass inside shells of constant thickness (0.05e10cm) and different outer radii:

https://guidarellig.github.io/MassInsideShellsp4R.png

Mass inside cylinder of disk height and radius 0.75e10 cm:

https://guidarellig.github.io/MassInDiskp75R.png

Mass inside hollow cylinder of disk height, constant thickness (0.125e10cm) and different radii:

https://guidarellig.github.io/MassInRingsp75R.png