<div dir="ltr"><div class="gmail_default" style="font-family:tahoma,sans-serif;font-size:small">Hi Lucas,</div><div class="gmail_default" style="font-family:tahoma,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif;font-size:small">I'm surprised that you're getting this result. I've been using nearly the same setup - i.e. 2D cyclindrical symmetry, uniform B = Bz, USM, with those same parameter settings. I haven't had any problems with divb. I think the only difference is the magnitude of B - as well as whatever else you're setting up in terms of densities, pressures and velocities. Which version of FLASH are you using? I'm using FLASH 4.3. I'm wondering if something strange could be happening when the energy is dominated by the magnetic field.</div><div class="gmail_default" style="font-family:tahoma,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:tahoma,sans-serif;font-size:small">Regards,</div><div class="gmail_default" style="font-family:tahoma,sans-serif;font-size:small">Jon</div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Apr 24, 2018 at 1:00 PM, <span dir="ltr"><<a href="mailto:flash-users-request@flash.uchicago.edu" target="_blank">flash-users-request@flash.uchicago.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Send flash-users mailing list submissions to<br>
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<br>Today's Topics:<br>
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1. Divergence of magnetic field (Lucas Rubio Fermoso)<br>
<br><br>---------- Forwarded message ----------<br>From: Lucas Rubio Fermoso <<a href="mailto:l.rubiof@alumnos.upm.es">l.rubiof@alumnos.upm.es</a>><br>To: <a href="mailto:flash-users@flash.uchicago.edu">flash-users@flash.uchicago.edu</a><br>Cc: <br>Bcc: <br>Date: Tue, 24 Apr 2018 11:43:49 +0200<br>Subject: [FLASH-USERS] Divergence of magnetic field<br>Dear all,<br>
<br>
I am trying to run a 2D cylindrical simulation with a high uniform initial magnetic field in the "Z" direction (~100 T), but I am getting very high divergence values that cascade in other errors forward in the simulation.<br>
<br>
This divergence is generated at the cells in the block boundaries perpendicular to the field, while being 0 everywhere else.<br>
<br>
Divergence values are created at the first step and they evolve during "nrefs" steps, after that the values get frozen for the rest of the simulation.<br>
<br>
For example: For "nrefs"=2 initial divergence is 0 everywhere, divergence changes at steps 1, 2 and 3 and then keeps the same values of step 3.<br>
<br>
For "nrefs"=4 is the same but evolves up to step 5.<br>
<br>
The problem seems related to how paramesh handles fluxes before it starts refining.<br>
<br>
I have tried to restart the simulation on the initial checkpoint so paramesh redistributes blocks on start, but did not work.<br>
<br>
Some parameters that may be important:<br>
Grid is Paramesh4<br>
Prolongation methods: injection and balsara, both used with little difference (It should be used balsara since the simulation is cylindrical)<br>
Solver: Unsplit Staggered Mesh<br>
killdivb = true<br>
flux_correct = true<br>
E_modification = true<br>
energyfix = true<br>
<br>
In simulation_initBlock magnetic field face values and magnetic field cell values are declared with the same value.<br>
<br>
Thanks in advance for your help.<br>
<br>
Best regards,<br>
-- <br>
Lucas Rubio Fermoso<br>
Universidad Politecnica de Madrid<br>
<br>
<br>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><div dir="ltr">________________________________________________________<br>Jonathan D. Slavin Harvard-Smithsonian CfA<br><a href="mailto:jslavin@cfa.harvard.edu" target="_blank">jslavin@cfa.harvard.edu</a> 60 Garden Street, MS 83<br>phone: (617) 496-7981 Cambridge, MA 02138-1516<br>cell: (781) 363-0035 USA<br>________________________________________________________<br><br></div></div></div></div>
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