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<p class="MsoNormal"><span style="font-size:11.0pt">Hi Edouardo,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">We have verified that the Nernst term in FLASH works accurately for a semi-analytical problem, but we have just started using this term to model real-world problems. We’re actively investigating which settings
work best, and we’ll be able to provide more guidance as we learn more.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">If it helps, there are a couple of terms associated with turning on Nernst that your problem may be able to safely ignore…<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">Ettingshausen – the qx, ay, and qz heat flux terms in hy_uhd_addNernstFluxes.F90<o:p></o:p></span></li><li class="MsoListParagraph" style="margin-left:0in;mso-list:l0 level1 lfo1"><span style="font-size:11.0pt">The j.E term associated with Nernst in hy_uhd_getFaceFlux.F90, which would require commenting blocks such as lines 675-694 in that file.<o:p></o:p></span></li></ol>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">It’s possible that turning off one or both of these will avoid the error.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:black">--</span><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:#181A1B">Eddie Hansen</span><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:#181A1B">Applications Group Leader<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-family:"Arial",sans-serif;color:#181A1B">Flash Center for Computational Science</span><span style="font-size:10.0pt;font-family:"Calibri",sans-serif;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt"><b><span style="color:black">From:
</span></b><span style="color:black">flash-users <flash-users-bounces@flash.rochester.edu> on behalf of Rover, Edoardo <erover@UCSD.EDU><br>
<b>Date: </b>Monday, January 27, 2025 at 12:36 PM<br>
<b>To: </b>flash-users@flash.rochester.edu <flash-users@flash.rochester.edu><br>
<b>Subject: </b>[FLASH-USERS] Negative 3T Internal Energy when including Nernst<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Dear FLASH users,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">I am attempting to implement extended-MHD in my simulation, and started by enabling the Nernst term in the simulation. However, I get a "Negative 3T Internal Energy" error. Following a previous user email, I attempted
to enable the flux limiter options for Nernst, and set them to:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">nernstFlMode = "fl_minmax"<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">nernstFlCoef = 0.08<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black">But the error presented itself once more. I previously attempted to use the "fl_larsen" option as well, and set the flux limiter to "0.09", the same value we are using for the electron conduction flux limiter,
but the problem persists. <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Setting "use_Nernst" to ".false." makes the simulation run without problems. Preheating the materials or changing the diffusion dt factor (or the radiation transport one) shows no changes, the simulation runs normally
if Nernst is set to False, while it crashes if set to True.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">For that reason, I think the issue lies entirely in the MHD setup block. Would you have any suggestions on the issue?<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Best regards,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:black">Edoardo Rovere<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="color:#0C64C0">Postdoctoral researcher<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:#0C64C0">UCSD CER<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:#0C64C0">3183 Matthews Ln 92093<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="color:#0C64C0">La Jolla (CA), US<o:p></o:p></span></p>
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