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<p class="MsoNormal"><span style="font-size:11.0pt">Hi </span><span style="font-size:11.0pt">Yanhong,<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">Possibly naïve question but did you replace the equation of state in the MITgcm by an appropriate one for magma?
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Assuming so, I guess that you need to set your viscosity to high values for physical reasons (magma is viscous) and then adjust for numerical reasons (so model does not blow up) as pointed out by Christoph
and Martin.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Also, if I understand correctly, you have boundary in our ocean at the day/night limit which will create boundary currents. But magma are probably not wind driven, so not sure you can use the Munk boundary
layer for these boundary currents.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Cheers,<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt">David<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"><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">MITgcm-support <mitgcm-support-bounces@mitgcm.org> on behalf of Martin Losch <Martin.Losch@awi.de><br>
<b>Date: </b>Friday, November 15, 2024 at 9:46</span><span style="font-family:"Arial",sans-serif;color:black"> </span><span style="color:black">AM<br>
<b>To: </b>MITgcm Support <mitgcm-support@mitgcm.org><br>
<b>Subject: </b>Re: [MITgcm-support] Numerical instability when horizontal contrast of initial temperature is large<o:p></o:p></span></p>
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<p class="MsoNormal"><span style="font-size:11.0pt">Hi Yanhong,<br>
<br>
it’s very difficult to say because your setup involves many parameters that are untypical for Earth (where we have more experience).<br>
<br>
I would check your CFL numbers for advection ( u * dt / dx ), viscosity Ah dt/dx**2 (here I would use AhGrid < 1 to make sure that this part is stable), also vertical viscosity. I agree with Christoph, that the viscosity appears a little low. But you may need
viscosities that are large and maybe require implicit schemes that are only available for the vertical (in MITgcm). The Coriolis CFL number is probably also much different from Earth, so is gravity.<br>
<br>
Then you horizontal density gradients are probably huge leading to large flow velocities, right? Again large viscosities will be required to balance that.<br>
<br>
(don’t use bottom drag and no_slip_bottom together, it’s double counting the effect of the bottom)<br>
<br>
Martin<br>
<br>
> On 15. Nov 2024, at 08:43, Christoph Voelker <christoph.voelker@awi.de> wrote:<br>
> <br>
> Dear Yanhong,<br>
> <br>
> I have no idea what to choose as viscosity for a magma ocean, but I wondered about the viscosities: In the tutorial examples, which are made for water, one finds values like<br>
> <br>
> viscAr=1.E-3,<br>
> viscAh=5.E5,<br>
> <br>
> not so different from what you take. Should these values not be very much higher for Magma?<br>
> <br>
> Also, how are you prescribing the equation of state?<br>
> <br>
> Cheers, Christoph<br>
> <br>
> <br>
> On 15.11.24 08:31, </span><span style="font-size:11.0pt;font-family:MingLiU">赖</span><span style="font-size:11.0pt;font-family:"MS Gothic"">六娃</span><span style="font-size:11.0pt"> wrote:<br>
>> Hi,<br>
>> I’m trying to simulate the magma ocean in tidally locked lava planet.<br>
>> To speed up the simulation, the initial temperature is set to decrease from 3000 K at the substellar point (0,0) to 50 K at the side boundaries.<br>
>> Meanwhile, the initial temperature is vertically uniform.<br>
>> However, there is strong instability when I start this simulation. I tried to decrease the maximum initial temperature to 1700 K, and the horizontal contrast becomes to (1700-50) K, but it is still unstable.<br>
>> Is there any way I can simulate stably with this initial temperature setup?<br>
>> By the way, the tilmestep deltaT is 20 s.<br>
>> Thanks very much!!<br>
>> Yanhong<br>
>> Below is my data file:<br>
>> # ====================<br>
>> # | Model parameters |<br>
>> # ====================<br>
>> #<br>
>> # Continuous equation parameters<br>
>> &PARM01<br>
>> # tRef= 18.8, 16.3, 13.1, 10.4, 8.1, 6.0, 4.5,<br>
>> # 3.4, 2.7, 2.2, 1.8, 1.5, 1.2, 1.0, 0.9,<br>
>> tRefFile='T0solid_diffusion_160x72.bin',<br>
>> # tRef=44*1600.,<br>
>> sRef= 44*34.7,<br>
>> cosPower=1.,<br>
>> viscAr=1.E-3,<br>
>> viscAh=12.E5,<br>
>> no_slip_sides=.FALSE.,<br>
>> no_slip_bottom=.TRUE.,<br>
>> bottomDragLinear=1.E-3,<br>
>> #diffK4T=2.E12,<br>
>> diffKhT=1.E3,<br>
>> diffKrNrT=44*1.E-4,<br>
>> ivdc_kappa=100.,<br>
>> implicitDiffusion=.TRUE.,<br>
>> # eosType='JMD95Z',<br>
>> eosType='LINEAR',<br>
>> tAlpha=4.E-5,<br>
>> sBeta =0.E-4,<br>
>> saltStepping=.FALSE.,<br>
>> gravity=22,<br>
>> rhonil=3300.,<br>
>> rhoConst=2600.,<br>
>> HeatCapacity_Cp=1800.,<br>
>> implicitFreeSurface=.TRUE.,<br>
>> nonlinFreeSurf=4,<br>
>> select_rStar=2,<br>
>> hFacInf=0.2,<br>
>> hFacSup=2.0,<br>
>> exactConserv=.TRUE.,<br>
>> staggerTimeStep=.TRUE.,<br>
>> useCDscheme=.TRUE.,<br>
>> readBinaryPrec=64,<br>
>> tempAdvScheme=77,<br>
>> # usePickupBeforeC54=.TRUE.,<br>
>> rotationPeriod=69120.,<br>
>> # useCoriolis=.FALSE.,<br>
>> Tsolidus=1700.,<br>
>> Tliquidus=2000.,<br>
>> &<br>
>> # Elliptic solver parameters<br>
>> &PARM02<br>
>> cg2dMaxIters=1000,<br>
>> #cg2dTargetResidual=1.E-13,<br>
>> cg2dTargetResWunit=1.E-17,<br>
>> &<br>
>> # Time stepping parameters<br>
>> &PARM03<br>
>> niter0=0,<br>
>> nTimeSteps=20000000,<br>
>> #endTime=3110400000.,<br>
>> deltaT=10.0,<br>
>> # deltaTmom=100.0,<br>
>> # deltaTfreesurf=2000.0,<br>
>> # deltaTtracer=600.0,<br>
>> # deltaTClock =600.0,<br>
>> forcing_In_AB=.FALSE.,<br>
>> abEps=0.1,<br>
>> tauCD=321428.,<br>
>> tauThetaClimRelax=2000.0,<br>
>> # pickupStrictlyMatch=.FALSE.,<br>
>> chkptFreq=0.0,<br>
>> pChkptFreq=5000000.0,<br>
>> taveFreq=0.0,<br>
>> dumpFreq=5000000.0,<br>
>> diagFreq=31104000000.0,<br>
>> monitorFreq=31104000000.0,<br>
>> # monitorFreq=1.0,<br>
>> monitorSelect=2,<br>
>> &<br>
>> # Gridding parameters<br>
>> &PARM04<br>
>> usingSphericalPolarGrid=.TRUE.,<br>
>> # delRc= 20., 60., 85., 120., 165., 215., 265., 315.,<br>
>> # 365., 415., 465., 515., 565., 615., 665., 350.,<br>
>> # delRcFile='delRc.bin',<br>
>> delR= 10., 10., 10., 10., 10., 10., 10., 10., 10., 10., 20., 20., 20., 20., 20., 20.,<br>
>> 40., 40., 40., 40., 40., 60., 60., 60., 60., 80., 80., 80., 100., 100., 100., 100.,<br>
>> 100., 150., 150., 200., 200., 200., 200., 200., 300., 300., 300., 400.,<br>
>> rSphere=9E6,<br>
>> ygOrigin=-81.,<br>
>> xgOrigin=-180,<br>
>> delY=72*2.25,<br>
>> delX=160*2.25,<br>
>> &<br>
>> # Input datasets<br>
>> &PARM05<br>
>> bathyFile='topo3D_160x72_5400m_4walls.bin',<br>
>> # zonalWindFile='taux_Az1E-5mod_160x72.bin',<br>
>> # meridWindFile='tauy_Az1E-5mod_160x72.bin',<br>
>> thetaClimFile='sst3D_mod_160x72.bin',<br>
>> &<br>
>> _______________________________________________<br>
>> MITgcm-support mailing list<br>
>> MITgcm-support@mitgcm.org<br>
>> </span><a href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support"><span style="font-size:11.0pt">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</span></a><span style="font-size:11.0pt"><br>
> <br>
> -- <br>
> Christoph Völker<br>
> Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research<br>
> Am Handelshafen 12<br>
> 27570 Bremerhaven<br>
> <br>
> +49 (0)471-4831-1848<br>
> christoph.voelker@awi.de<br>
> </span><a href="https://orcid.org/0000-0003-3032-114X"><span style="font-size:11.0pt">https://orcid.org/0000-0003-3032-114X</span></a><span style="font-size:11.0pt"><br>
> <br>
> _______________________________________________<br>
> MITgcm-support mailing list<br>
> MITgcm-support@mitgcm.org<br>
> </span><a href="http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support"><span style="font-size:11.0pt">http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support</span></a><span style="font-size:11.0pt"><br>
<br>
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