wiki:u/erica/LowResMHDShearFlows

Version 41 (modified by Erica Kaminski, 11 years ago) ( diff )

3D MHD Shear Flows

Diameter40 pc
Mach1.5
Shear Angles15, 30, 60 degrees
Density1 cm-3
Beta1, 10, Hydro
Initial B-field orientationUniform in x, y, z
Cells/Jeans Length64
CoolingII curve
Final time20 Myr
Resolution48 + 2 ~ 200 cells effective
Box size62.5 x 75 x 75 pc in x,y,z
Boundary conditions Extrapolating, and multipole
Self-gravityOn

Orientation of Collision Interface

Plots showing the direction of the tilted interface:

Shear15 Shear30 Shear60

Interface is rotated about y.

Uniform X-field Case

Evolution of the tilted interface

A slice taken through the center of the box, in the x-z plane, shows that in the strong magnetic field case, the interface tends to realign so that it is vertical in z:

movie

Interestingly, the hydro case might also straighten out..?

Column Density Maps

These column density maps are made by summing the density over all cells through a given dimension, using both the gas and sink components. You can use the above 3D plot for orientation. In the 'down the barrel case', the vertical dimension is z, and the horizontal axis is y. The axes are given in the other plots.

'Down the Barrel' Down Y Down Z
movie movie movie

A strong ring effect is present in the strong beta cases that isn't in the weaker B field and hydro case. The ripples are also interesting, not sure whether they are numerical or physical yet.

Peak Densities and Sink Particles

Run Time when sink first appears Number of sinks by end
Beta1, Shear15 Frame 160/200, t=1.32 8
Beta1, Shear30 Frame 173/200, t=1.43 7
Beta1, Shear30 No Sinks Form 0
Beta10, Shear15 Frame 184/200, t=1.5 5
Beta10, Shear30 Frame 161/200, t=1.3 2
Beta10, Shear30 Frame 196/200, t=1.6 1
Hydro, Shear15 Frame 118/200, t=0.97 6
Hydro, Shear30 Frame 146/200, t=1.2 3
Hydro, Shear60 No Sinks Form 0

X, Y, & Z magnetic field cases

Beta = 1

Was not obvious which field orientation would be best to use for the transverse (i.e. perpendicular to the flow direction) field run, since the shear angle breaks the symmetry of the cylinder. So to compare the difference, here are 3D low runs of the Shear 15, Beta=1 case.

In column density, the transverse runs (y-field and z-field) are mirror images of each other. This can be seen at once looking down the barrel in x. When looking transversely, orient yourself to the direction of the incoming flow along x, then consider the direction of the field using the coordinate axes at bottom of each column. You will see that the same behavior is seen between the different orientations. That is, the middle box has same behavior as bottom right box, when you consider the relative directions of the field and the colliding flows.

And here are the 3 different initial conditions for orientation:

Bx

By

Bz

Further, peak densities were similar in the transverse cases and both did not form sinks,

B-field Direction Peak Density at .25, .50, .75, 1 Time first sink formed No. of sinks by end
x 229, 947, 2383, 4934 15 Myr 8
y 27, 58, 69, 88 -No sinks form- 0
z 22, 51, 50, 58 -No sinks form- 0

Beta = 10

B-field Direction Peak Density at .25, .50, .75, 1 Time first sink formed No. of sinks by end
x 598, 1140, 1535, 1487 18 Myr 5
y 83, 210, 255, 225 -No sinks form- 0
z 58, 132, 194, 163 -No sinks form- 0

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