[FLASH-USERS] Change in mass and energy after first step

[Klaus Weide]

On Wed, 30 Mar 2016, Drake Alexander Ranquist wrote:

> I am grad student who is new to using Flash and scientific computing in
> general.  I am trying to simulate the solar wind’s interaction with
> Jupiter.  I ran a simple test of initializing the solar wind in a closed
> box.  After the first time step, the mass immediately jumped up (the low
> density I initialize it with probably is over written by a minimum density)
> and the magnetic energy dropped by 31 orders of magnitude.

1) Review all the runtime parameters named "small*" and set them
   to valus that can be considered small compard to typical values that
   you expect physically in your simulation.
   (You also may have to adjust other parameters, in particular
   dtmin, dtmax, dtinit.)

> I am trying to initialize everything with SI units instead of
> non-dimensional ones, but I’m not convinced that I did things right.  It
> would be really nice if someone looked through what I’ve done and let me
> know of all of the beginner’s mistakes I’ve made.

2) FLASH with SI units, in particular
    pc_unitsBase = "MKS" ,
   is not well tested.  You would be on the safer side if you used cgs 
   units like most FLASH applications do.
   Contributed fixes to make SI units work better would be welcome.

3) Since you are using MHD, your simulation directory should be under
   "magnetoHD", so you should move it from

      Simulation/SimulationMain/JovSim

   to

      Simulation/SimulationMain/magnetoHD/JovSim .

4) Your Simulation_initBlock needs to initialize face variables for the 
   magnetic B field in addition to the cell-centered magx, magy, magz 
   variables.  You should be able to find examples in other magnetoHD
   simulations.

Klaus