Tests

Half Grid v.s Full Grid

Our simulations take advantage of the symmetry of these problems and only evolve the right half of the grid, which is then simply reflected to provide a visualization for the whole jet. We decided to run one full grid simulation to compare, just to make sure there are no boundary effects. This run is the stratified diverging wind, with the MHD equations turned on and \beta = 100000 (so essentially no magnetic fields). If we compare this to the hydro stratified diverging wind run from the previous section, we see that the symmetry of the problem is indeed preserved.

MHD Bubbles

Our initial runs show very distinct bubbles in the MHD runs that don't exist in the hydro case. While the MHD flows should be m = 0 unstable, there may be something else going on as well. The following images are from the same conditions, one purely hydro, one with MHD and \beta = .8 and the third MHD with a high \beta. As we cantsee, the bubbles are very nonexistant in the hydro case, distinct in the MHD case and mild in the high \beta case.

We have also tried running the weak magnetic field cases, with \beta = 8 and \beta = 80:

Martin, 29 July 2013. Found and fixed a bug in our module, which affected the strength of magnetic fields. Running test to see whether this gets rid of the bubble-looking features, which i think are unphysical, that we see in the mhd cases.

The current runs have been updated with a solution to this issue. You can look through the old data ​here.

Torus

In our initial runs, the torus case seems to not be very different from the constant ambient case. We are trying different values of \alpha_{t}, the density contrast to see where there is a significant impact of the torus. So far, we have tried values of:
\alpha = .3 ​movie

\alpha = .9 ​movie

Our current idea is that the setup of the Torus is in such a way that it will not have a great effect on the shaping of the lobe past the origin. Our new runs now reflect a mroe physical situation that combines a 1/r² density dropoff along with the torus setup. You can find the data from our old setup ​here.

Hi-Res Diverging Wind Model

​movie

Comparison of MHD to Hydro Jets in Different Ambient Media

Constant: ​movie

Stratified: ​movie

Toroidal: ​movie