## some units problems when I join the sliding section

Extension of Elmer in computational glaciology
zhang liangfu
Posts: 22
Joined: 20 Nov 2014, 05:06
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### some units problems when I join the sliding section

velocity.JPG
hello everyone,
Recently I was doing some research in the antarctica ice berg ,I am trying using the elmer/ice model to simulating the dynamics and thermodynamics . when I do this ,I encounter many problem,can any one give me some help?
my problem as folows :
first ,the sliding section . http://elmerfem.org/forum/viewtopic.php ... 44e6d625afas this paper say ,I encounter the same question,I do not know the differences between the two units,and I just don't know How I set the Slip Coefficient 2 and the Slip Coefficient3.
second ,when I set the two parameters as
Flow Force BC = Logical True
Normal-Tangential Velocity = Logical True
Velocity 1 = Real 0.0e0
Slip Coefficient 2 = Real 1000
Slip Coefficient 3 = Real 1000
I obtain a velocity as follows:
I find the velocity is very big .I just do not know the unit of the velocity.
third,I have not sucessfully the transient simulation and every time the problem as follows
StructuredMeshMapper: >Correct Surface< in case of intersecting upper and lower surface
StructuredMeshMapper: Adjusting upper surface to maintain minimum height to: 0.1000E+01
FlowdepthSolver: Memory allocation done.
FlowdepthSolver: Gradient of -0.1000E+01 applied
ComputeChange: NS (ITER=1) (NRM,RELC): ( 1461.5746 2.0000000 ) :: flowdepth
6 0.5581E-04
ComputeChange: NS (ITER=1) (NRM,RELC): ( 0.31434882E-02 2.0000000 ) :: navier-stokes
6 0.3257E-04
ComputeChange: NS (ITER=2) (NRM,RELC): ( 4.7611171 1.9973608 ) :: navier-stokes
6 0.4033E-04
ComputeChange: NS (ITER=3) (NRM,RELC): ( 668.09704 1.9716962 ) :: navier-stokes
5 0.9756E-04
ComputeChange: NS (ITER=4) (NRM,RELC): ( 18348.357 1.8594697 ) :: navier-stokes
5 0.8676E-04
ComputeChange: NS (ITER=5) (NRM,RELC): ( 167891.39 1.6059196 ) :: navier-stokes
5 0.7492E-04
ComputeChange: NS (ITER=6) (NRM,RELC): ( 735774.68 1.2568432 ) :: navier-stokes
7 0.7430E-04
ComputeChange: NS (ITER=7) (NRM,RELC): ( 4189989.2 1.4025092 ) :: navier-stokes
7 0.4910E-04
ComputeChange: NS (ITER=8) (NRM,RELC): ( 10082247. 0.82569508 ) :: navier-stokes
6 0.4472E-04
ComputeChange: NS (ITER=9) (NRM,RELC): ( 13478271. 0.28828093 ) :: navier-stokes
4 0.5723E-04
ComputeChange: NS (ITER=10) (NRM,RELC): ( 14112872. 0.46000357E-01 ) :: navier-stokes
2 0.7456E-04
ComputeChange: NS (ITER=11) (NRM,RELC): ( 14156438. 0.30821840E-02 ) :: navier-stokes
1 0.5027E-04
ComputeChange: NS (ITER=12) (NRM,RELC): ( 14165516. 0.64110647E-03 ) :: navier-stokes
ComputeChange: NS (ITER=1) (NRM,RELC): ( 12.431605 2.0000000 ) :: sij
ComputeChange: NS (ITER=2) (NRM,RELC): ( 12.476920 0.36385089E-02 ) :: sij
ComputeChange: NS (ITER=3) (NRM,RELC): ( 13.013476 0.42098643E-01 ) :: sij
ComputeChange: NS (ITER=4) (NRM,RELC): ( 0.16314306 1.9504750 ) :: sij
ComputeChange: NS (ITER=5) (NRM,RELC): ( 0.61319196 1.1594193 ) :: sij
ComputeChange: NS (ITER=6) (NRM,RELC): ( 0.73213325 0.17682162 ) :: sij
ComputeChange: NS (ITER=1) (NRM,RELC): ( 239530.40 2.0000000 ) :: deformationalheat
TemperateIceSolver (temp): Memory allocation done
0 : 0 ghost nodes
TemperateIceSolver (temp): Limited diffusion Solver for variable temp
TemperateIceSolver (temp): Variational inequality applied
0 : Max/min values Temperature: 274.54354757639544 / 222.60072541993733
1 0.1482E-05
2 0.1998E-10
2 0.1998E-10
ComputeChange: NS (ITER=1) (NRM,RELC): ( 3460.0068 2.0000000 ) :: homologous temperature equation
0 : Number of constrained points: 6454
0 : Max/min values Temperature: 203191.91297230791 / -4609.9352275149840
1 0.3294E-06
2 0.6719E-12
2 0.6719E-12
ComputeChange: NS (ITER=2) (NRM,RELC): ( 273.36899 1.7071080 ) :: homologous temperature equation
0 : Number of constrained points: 6318
0 : Max/min values Temperature: 1437.5403838625793 / 141.81813128762255
1 0.6554E-07
2 0.3420E-12
2 0.3420E-12
ComputeChange: NS (ITER=3) (NRM,RELC): ( 678.45483 0.85117819 ) :: homologous temperature equation
0 : Number of constrained points: 7096
0 : Max/min values Temperature: 66017.518395604435 / -9313.7889683524772
1 0.1373E-06
2 0.3626E-07
3 0.3626E-07
4 0.3626E-07
5 0.3626E-07
6 0.3626E-07
7 0.3626E-07
8 0.1091E-41
ERROR:: IterSolve: Failed convergence tolerances.

by the way ,How I can obtain the same picture through the vtu file

any help is very thankful ,looking forward to you
yours sincerely liangfu
Attachments section.JPG (67.21 KiB) Viewed 3202 times

tzwinger
Posts: 87
Joined: 24 Aug 2009, 12:20
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### Re: some units problems when I join the sliding section

Hello,
the units (and hence the value) of the coefficient for the sliding law depends on the rest of you units. Elmer doesn't restrict you on that. If you use SI units (m-kg-seconds) then the unit for the friction coefficient (the beta^2 as decribed for instance in ISMIP-HOM experiments for linear sliging) would be Pa s/m, if you use (what would apply if you copied the setup I made for Dome A) m-MPa-years, then the unit would be (linear sliding) MPa year/m.

The picture you attached has been produce by me from VTU output of the Dome A runs and needs a difficult combination of slices produced in ParaView and a later combination of the different pictures using a stone-age old program called xfig. In short, it is too complicated a procedure to guide you through. But, you can get those slices (vertical and horizontal) very well in ParaView and then combine them by ever program you like (e.g. Paint)

Best wishes,

Thomas