[MITgcm-support] Numerical instability when horizontal contrast of initial temperature is large
Giordano, Fabio
fgiordano at ogs.it
Fri Nov 15 05:30:55 EST 2024
Hi Martin,
I would like to chime in about the bottom drag issue: does the double
counting occur by setting the logical parameter `no_slip_bottom` to TRUE
together
1) with non-zero linear or quadratic drag coefficients, or
2) only with the linear one?
I am looking at the source code and by my understanding it seems to be the
latter, but I could be mistaken.
Thank you,
Fabio Giordano
Sezione di Oceanografia
Istituto Nazionale di Oceanografia e di Geofisica Sperimentale - OGS
via Beirut n. 2
34151 Trieste - Italia
Il giorno ven 15 nov 2024 alle ore 10:46 Martin Losch <Martin.Losch at awi.de>
ha scritto:
> Hi Yanhong,
>
> it’s very difficult to say because your setup involves many parameters
> that are untypical for Earth (where we have more experience).
>
> 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.
>
> Then you horizontal density gradients are probably huge leading to large
> flow velocities, right? Again large viscosities will be required to balance
> that.
>
> (don’t use bottom drag and no_slip_bottom together, it’s double counting
> the effect of the bottom)
>
> Martin
>
> > On 15. Nov 2024, at 08:43, Christoph Voelker <christoph.voelker at awi.de>
> wrote:
> >
> > Dear Yanhong,
> >
> > 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
> >
> > viscAr=1.E-3,
> > viscAh=5.E5,
> >
> > not so different from what you take. Should these values not be very
> much higher for Magma?
> >
> > Also, how are you prescribing the equation of state?
> >
> > Cheers, Christoph
> >
> >
> > On 15.11.24 08:31, 赖六娃 wrote:
> >> Hi,
> >> I’m trying to simulate the magma ocean in tidally locked lava planet.
> >> 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.
> >> Meanwhile, the initial temperature is vertically uniform.
> >> 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.
> >> Is there any way I can simulate stably with this initial temperature
> setup?
> >> By the way, the tilmestep deltaT is 20 s.
> >> Thanks very much!!
> >> Yanhong
> >> Below is my data file:
> >> # ====================
> >> # | Model parameters |
> >> # ====================
> >> #
> >> # Continuous equation parameters
> >> &PARM01
> >> # tRef= 18.8, 16.3, 13.1, 10.4, 8.1, 6.0, 4.5,
> >> # 3.4, 2.7, 2.2, 1.8, 1.5, 1.2, 1.0, 0.9,
> >> tRefFile='T0solid_diffusion_160x72.bin',
> >> # tRef=44*1600.,
> >> sRef= 44*34.7,
> >> cosPower=1.,
> >> viscAr=1.E-3,
> >> viscAh=12.E5,
> >> no_slip_sides=.FALSE.,
> >> no_slip_bottom=.TRUE.,
> >> bottomDragLinear=1.E-3,
> >> #diffK4T=2.E12,
> >> diffKhT=1.E3,
> >> diffKrNrT=44*1.E-4,
> >> ivdc_kappa=100.,
> >> implicitDiffusion=.TRUE.,
> >> # eosType='JMD95Z',
> >> eosType='LINEAR',
> >> tAlpha=4.E-5,
> >> sBeta =0.E-4,
> >> saltStepping=.FALSE.,
> >> gravity=22,
> >> rhonil=3300.,
> >> rhoConst=2600.,
> >> HeatCapacity_Cp=1800.,
> >> implicitFreeSurface=.TRUE.,
> >> nonlinFreeSurf=4,
> >> select_rStar=2,
> >> hFacInf=0.2,
> >> hFacSup=2.0,
> >> exactConserv=.TRUE.,
> >> staggerTimeStep=.TRUE.,
> >> useCDscheme=.TRUE.,
> >> readBinaryPrec=64,
> >> tempAdvScheme=77,
> >> # usePickupBeforeC54=.TRUE.,
> >> rotationPeriod=69120.,
> >> # useCoriolis=.FALSE.,
> >> Tsolidus=1700.,
> >> Tliquidus=2000.,
> >> &
> >> # Elliptic solver parameters
> >> &PARM02
> >> cg2dMaxIters=1000,
> >> #cg2dTargetResidual=1.E-13,
> >> cg2dTargetResWunit=1.E-17,
> >> &
> >> # Time stepping parameters
> >> &PARM03
> >> niter0=0,
> >> nTimeSteps=20000000,
> >> #endTime=3110400000.,
> >> deltaT=10.0,
> >> # deltaTmom=100.0,
> >> # deltaTfreesurf=2000.0,
> >> # deltaTtracer=600.0,
> >> # deltaTClock =600.0,
> >> forcing_In_AB=.FALSE.,
> >> abEps=0.1,
> >> tauCD=321428.,
> >> tauThetaClimRelax=2000.0,
> >> # pickupStrictlyMatch=.FALSE.,
> >> chkptFreq=0.0,
> >> pChkptFreq=5000000.0,
> >> taveFreq=0.0,
> >> dumpFreq=5000000.0,
> >> diagFreq=31104000000.0,
> >> monitorFreq=31104000000.0,
> >> # monitorFreq=1.0,
> >> monitorSelect=2,
> >> &
> >> # Gridding parameters
> >> &PARM04
> >> usingSphericalPolarGrid=.TRUE.,
> >> # delRc= 20., 60., 85., 120., 165., 215., 265., 315.,
> >> # 365., 415., 465., 515., 565., 615., 665., 350.,
> >> # delRcFile='delRc.bin',
> >> delR= 10., 10., 10., 10., 10., 10., 10., 10., 10., 10., 20., 20., 20.,
> 20., 20., 20.,
> >> 40., 40., 40., 40., 40., 60., 60., 60., 60., 80., 80., 80.,
> 100., 100., 100., 100.,
> >> 100., 150., 150., 200., 200., 200., 200., 200., 300., 300.,
> 300., 400.,
> >> rSphere=9E6,
> >> ygOrigin=-81.,
> >> xgOrigin=-180,
> >> delY=72*2.25,
> >> delX=160*2.25,
> >> &
> >> # Input datasets
> >> &PARM05
> >> bathyFile='topo3D_160x72_5400m_4walls.bin',
> >> # zonalWindFile='taux_Az1E-5mod_160x72.bin',
> >> # meridWindFile='tauy_Az1E-5mod_160x72.bin',
> >> thetaClimFile='sst3D_mod_160x72.bin',
> >> &
> >> _______________________________________________
> >> MITgcm-support mailing list
> >> MITgcm-support at mitgcm.org
> >> http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
> >
> > --
> > Christoph Völker
> > Alfred Wegener Institute, Helmholtz Centre for Polar and Marine Research
> > Am Handelshafen 12
> > 27570 Bremerhaven
> >
> > +49 (0)471-4831-1848
> > christoph.voelker at awi.de
> > https://orcid.org/0000-0003-3032-114X
> >
> > _______________________________________________
> > MITgcm-support mailing list
> > MITgcm-support at mitgcm.org
> > http://mailman.mitgcm.org/mailman/listinfo/mitgcm-support
>
> _______________________________________________
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