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<p class="MsoNormal"><span style="font-size:11.0pt">Hello,<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">The ‘chi’ that you are referring to is different between those two routines on purpose, but it’s not because of different B-field units…<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">The fits for the kappa’s from Ji & Held, Phys. Plasmas 20, 042144, 2013 use a collision time tau that is multiplied by an extra factor of Z. So with chi = omega*tau, the chi‘s in JiHeld/Conductivity_anisoFullState
vs DaviesWen/Thermoelectric_fullState are different by a factor of Z. <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">The flux limiters for the Thermoelectric effects (e.g., Nernst) are not well-tested yet. They were implemented because we knew they might be needed in the future. This topic is addressed in Davies, et al.,
Phys. Plasmas 22, 112703 (2015).<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;color:black">--</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:#181A1B">Eddie Hansen</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:#181A1B">Research Scientist</span><span style="color:black"><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:12.0pt;font-family:"Arial",sans-serif;color:#181A1B">Flash Center for Computational Science</span><span style="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="font-size:12.0pt;color:black">From:
</span></b><span style="font-size:12.0pt;color:black">flash-users <flash-users-bounces@flash.rochester.edu> on behalf of Loffelmann, Jiri <loffejir@fjfi.cvut.cz><br>
<b>Date: </b>Monday, May 15, 2023 at 1:43 PM<br>
<b>To: </b>flash-users@flash.rochester.edu <flash-users@flash.rochester.edu><br>
<b>Subject: </b>[FLASH-USERS] E-MHD Aniso conductivity BUG<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Hello FLASH users,<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I have two questions for you.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">#1<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I noticed an error in the computation of anisotropic thermal conduction coefficients inside the new FLASH version 4.7 and I would like to check that my belief is correct.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">In my E-MHD simulations, using all the newly added MHD terms (Seebeck, Nernst, CrossNernst, aniso. thermal cond.), the magnetic advection velocity corresponding to the Nernst term is in some situations
similar or even greater than the advection of temperature due to grad(T) in the direction perpendicular to the magnetic field.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Using the formalism from this paper
<a href="https://iopscience.iop.org/article/10.1088/1741-4326/ac25c1">https://iopscience.iop.org/article/10.1088/1741-4326/ac25c1</a>: <o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"> gamma_perp >= kappa_perp<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">In addition, in the paper in Figure 2, there is clearly visible, that the ratio of these transport coefficients, <span class="contentpasted2"><span style="background:white">kappa_perp /
</span></span><span class="contentpasted3"><span style="background:white">gamma_perp</span></span><span class="contentpasted2"><span style="background:white">, </span></span>should be always greater than 3.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Therefore, I suspect an implementation error in the computation of the kappa_pepr coefficient.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">When reading through the two files that compute kappa_perp and gamma_perp coefficients:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">/FLASH4.7/source/physics/materialProperties/Conductivity/ConductivityMain/JiHeld/Conductivity_anisoFullState.F90<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">/FLASH4.7/source/physics/materialProperties/Thermoelectric/ThermoelectricMain/DaviesWen/Thermoelectric_fullState.F90<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I noticed that the computation is very similar and truly, for the same values of magnetization ('chi'), it gives the coefficients with the correct ratio.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Finally, I discovered that both codes compute different values of magnetization, with a difference of sqrt(4.0*PI).<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I believe that in Conductivity_anisoFullState, the magnetic field is in Gaussian units and in Thermoelectric_fullState it is in different physical units. And since the computation of the magnetization
is precisely the same, it differs in the end. I am not really sure why the units are different, as I am not as familiar with all of the code, but either way, I believe the magnetization should be the same...<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I propose a quick fix:<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">add line 'xmag = xmag / sqrt(4.0*PI)' after line number 133, in file <span class="contentpasted11"><span style="background:white">Conductivity_anisoFullState.F90.</span></span><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">I am happy to provide further details and the setup of the simulation where the incorrect fraction appears.<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-size:12.0pt;color:black;background:white">2#</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-size:12.0pt;color:black;background:white">Secondly, I would like to ask about the usage of flux limiters for the Nernst and CrossNernst terms in the E-MHD model inside FLASH.</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-size:12.0pt;color:black;background:white">I would like to use E-MHD for the laser-target problems and I am wondering what values to use for 'nernstflcoef' and 'crossfieldflcoef'?</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-size:12.0pt;color:black;background:white">Do you have any references or experience with this?</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black">Should I use the same value as for thermal diffusion (diff_eleFlCoef)? When for laser-target problems, it is usually reasonable to set <span style="background:white">diff_eleFlCoef = </span>0.05-0.1...<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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<p class="MsoNormal" style="background:white"><span style="font-size:12.0pt;color:black">Regards,<o:p></o:p></span></p>
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<p class="MsoNormal"><span class="contentpasted0"><span style="font-size:12.0pt;color:black;background:white">Jiří Löffelmann</span></span><span style="font-size:12.0pt;color:black"><o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:12.0pt;color:black"><o:p> </o:p></span></p>
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