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Jon,</div>
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I remember I have emailed you.</div>
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I did some HD, MHD, and RHD work on supernova remnants, though not using FLASH.</div>
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You have to check the ghost zones, implementing the velocity gradiant. As pressure is trivial, the problem should arise from the velocity gradiant of the ghostzone not setting correctly, if not from PPM. (Density gradient is important, too).</div>
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You need to set up the condition like a free-expanding ejecta. Don't just use the
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boundary </span>condition options from the code; modify the BC. </div>
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Chih-Yueh Wang</div>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> flash-users-bounces@flash.uchicago.edu <flash-users-bounces@flash.uchicago.edu> on behalf of Slavin, Jonathan <jslavin@cfa.harvard.edu><br>
<b>Sent:</b> Thursday, March 29, 2018 9:29 PM<br>
<b>To:</b> flash-users<br>
<b>Subject:</b> [FLASH-USERS] noisiness in run with high ekin/eint</font>
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Hi,</div>
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I've been doing runs in 1D spherical symmetry of supernova remnants starting with fast cool ejecta. This is one of those situations in which the kinetic energy far exceeds the thermal energy (at least in the early stages). </div>
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I know about eintSwitch which is supposed to help with numerical issues that arise in such situations, but I've been finding that setting it lower actually results in less noisiness, though the noisiness that remains is, if nothing else, unsightly. What happens
is that the pressure develops fairly large fluctuations that seem to be purely numerical since there doesn't seem to be any other source for them. The pressure is small in those regions, relative to the kinetic energy, but still the noise seems to affect
the density. </div>
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So I'm wondering if others have found parameter settings or approaches that work well in this sort of situation. If so, I'd like to hear about them. I should mention that I've been using split PPM. I did try to use unsplit hydro but it failed with the pressure
dropping to the smallp value very quickly. I may try to investigate that some more.</div>
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Regards,</div>
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Jon</div>
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<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>
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