<div dir="ltr"><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">Hi Ernesto,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">That worked! Just setting addThermalFlux to False prevents the crashes I was getting and so far the results look good.  The run that I'm doing now has the magnetic field set to zero, so I haven't tested what happens with a non-zero field yet.  However, as I noted before, even a zero B field was causing crashes previously.  So thank you very much for that tip!</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small"><br></div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">Regards,</div><div class="gmail_default" style="font-family:arial,helvetica,sans-serif;font-size:small">Jon</div><div class="gmail_extra"><br><div class="gmail_quote">On Mon, Aug 14, 2017 at 5:50 PM, Slavin, Jonathan <span dir="ltr"><<a href="mailto:jslavin@cfa.harvard.edu" target="_blank">jslavin@cfa.harvard.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div class="gmail_extra"><div class="gmail_quote"><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">​Hi Ernesto,</div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline"><br></div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">I maybe should have mentioned that my runs have been in 2D (cylindrical).  So have you done such runs?  Also for the conduction, I'm using unsplit diffusion with electron thermal conduction and power law conductivity.  You mention being careful with split vs. unsplit diffusion, but you don't say which one works - or what that means to be careful.​</div> <div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">​ Or is it just that parameter setting addThermalFlux? I'll try setting that to False to see if that helps.</div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline"><br></div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">To answer your question, I'm not using super-time-stepping.  Didn't seem necessary since with Crank Nicholson diffusion you have unconditional stability.  So I haven't looked into how to use that.</div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline"><br></div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">Thanks for the suggestions.</div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline"><br></div></div><div><div style="font-family:arial,helvetica,sans-serif;font-size:small;display:inline">Jon ​</div></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class="">---------- Forwarded message ----------<br>From: ERNESTO ZURBRIGGEN <<a href="mailto:ezurbriggen@unc.edu.ar" target="_blank">ezurbriggen@unc.edu.ar</a>><br>To: <a href="mailto:flash-users@flash.uchicago.edu" target="_blank">flash-users@flash.<wbr>uchicago.edu</a><br>Cc: <br>Bcc: <br>Date: Mon, 14 Aug 2017 12:18:31 -0300<br>Subject: Re: [FLASH-USERS] combining MHD and thermal conduction<br></span><div dir="ltr"><span class="">Hi Jon! <div><br></div><div><span style="font-family:arial,helvetica,sans-serif">>It made me wonder if there is some numerical way that the implementations of thermal conduction and MHD interfere with each other.</span></div><div><font face="arial, helvetica, sans-serif"><br></font></div></span><div><font face="arial, helvetica, sans-serif">I have used MHD+(isotropic) Conduction without any problem of that sort. One confusing thing is that you can select Diffusion/split and Diffuse/unsplit. Be careful with that. </font></div><div><font face="arial, helvetica, sans-serif"><br></font></div><div><font face="arial, helvetica, sans-serif">Something curious is that if the simulation include unsplit/MHD + (regardless of </font><span style="font-family:arial,helvetica,sans-serif">split or </span><span style="font-family:arial,helvetica,sans-serif">unsplit) </span><span style="font-family:arial,helvetica,sans-serif">Diffusion</span><span style="font-family:arial,helvetica,sans-serif"> you have to also set the runtime parameter addThermalFlux=.false. (.true. by default)</span></div><div><font face="arial, helvetica, sans-serif">Otherwise, you are including the thermal conduction effect twice, i.e., </font><span style="font-family:arial,helvetica,sans-serif">heat </span><span style="font-family:arial,helvetica,sans-serif">diffusion via the HYPRE libraries decoupling the heat equation, and adding the thermal flux to the total energy flux in the Hydro unit.  </span></div><div><span style="font-family:arial,helvetica,sans-serif">I think the most consistent configuration would be unsplit/MHD + Diffusion/</span><span style="font-family:arial,helvetica,sans-serif">unsplit</span><span style="font-family:arial,helvetica,sans-serif"> + addThermalFlux=.false.</span></div><span class=""><div><span style="font-family:arial,helvetica,sans-serif"><br></span></div><div><span style="font-family:arial,helvetica,sans-serif"><br></span></div><div><span style="font-family:arial,helvetica,sans-serif">>I tried reducing the conductivity further and found that only by reducing it by many orders of magnitude (~8) was I able to get runs that didn't crash </span><span style="font-family:arial,helvetica,sans-serif"><br></span></div><div><font face="arial, helvetica, sans-serif"><br></font></div></span><div><font face="arial, helvetica, sans-serif">Maybe you can try reducing the parameter dt_diff_factor. </font></div><div><font face="arial, helvetica, sans-serif"><br></font></div><div><font face="arial, helvetica, sans-serif">Are you using super-time-stepping?  </font></div><div><font face="arial, helvetica, sans-serif"><br></font></div><div><font face="arial, helvetica, sans-serif">Best! </font></div><div><div>Ernesto. </div></div></div></blockquote></div></div></div></blockquote></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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