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solvers:ssa [2013/11/25 13:34] fgillet [SIF contents] |
solvers:ssa [2017/05/19 05:20] (current) tzwinger [General Description] |
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==== General Informations ==== | ==== General Informations ==== | ||
- | :!: **important | + | :!: **Important |
* **Solver Fortran File:** '' | * **Solver Fortran File:** '' | ||
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* (3) '' | * (3) '' | ||
* **Required Input Variable(s): | * **Required Input Variable(s): | ||
- | * (1) '' | + | * (1) '' |
* (2) '' | * (2) '' | ||
* (3) '' | * (3) '' | ||
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==== General Description ==== | ==== General Description ==== | ||
+ | |||
+ | === Ice flow === | ||
The '' | The '' | ||
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It will work on a 3D mesh only if the mesh as been extruded along the vertical direction and if the base line boundary conditions have been preserved (to impose neumann conditions). \\ | It will work on a 3D mesh only if the mesh as been extruded along the vertical direction and if the base line boundary conditions have been preserved (to impose neumann conditions). \\ | ||
- | The mandatory input variables are the bottom surface elevation and top surface elevation variables called | + | The mandatory input variables are the bottom surface elevation and top surface elevation variables called |
- | For the Flow law the SSA solver use a " | + | For the Flow law the SSA solver use a " |
- | Newton linearisation of the viscosity can be used usning | + | Newton linearisation of the viscosity can be used using the keywords |
- | //' | + | '' |
- | The //"Mean Density"// | + | The '' |
- | Contrary to the NS solver, the gravity must be orientated along the z-axis and it taken form the value of | + | Contrary to the NS solver, the gravity must be orientated along the z-axis and is taken from the value of |
- | //'' | + | '' |
- | A Neumann condition on the lateral boundaries can be applied with the keyword | + | A Neumann condition on the lateral boundaries can be applied with the keyword |
- | where | + | where\\ |
- | | + | |
- | | + | |
- | | + | |
- | | + | |
- | | + | |
- | Note that in the absence of explicit boundary condition (no dirichlet condition or "Calving front = Logical True" | + | Note that in the absence of explicit boundary condition (no dirichlet condition or '' |
- | The slip coefficient coefficient values are imposed in the // | + | The SSA velocities and pressure can be used, for example, as initial conditions for the Stokes Solver. |
- | //"SSA slip coefficient i = Real ..."// with i=1,2 \\ | + | |
- | The SSA velocities and pressure can be use, for example, as initial conditions for the Stokes Solver. \\ | ||
+ | When the SSA solution is computed on a boundary of a mesh of dimension larger than the SSA problem (e.g. a 3D mesh for a SSA-2D problem), the SSA solution computed on the boundary can be | ||
+ | * exported on the whole mesh using the '' | ||
+ | * used as a Dirichlet condition for the SIA velocity (see the [[solvers: | ||
- | When the SSA solution is computed on a boundary of a mesh of dimension larger than the SSA problem (e.g. a 3D mesh for a SSA-2D problem), the SSA solution computed on the boundary | + | === Basal friction === |
- | | + | |
- | - can be used as a dirichlet condition for the SIA velocity | + | Since version 6480, there are three friction laws implemented in the SSA solver: |
+ | |||
+ | * a linear friction law | ||
+ | < | ||
+ | * a Weertman type friction law | ||
+ | < | ||
+ | * a Coulomb type friction law | ||
+ | < | ||
+ | where | ||
+ | < | ||
+ | and | ||
+ | < | ||
+ | |||
+ | The two latests are non-linear and a Newton linearisation can be used. The friction law is chosen using the keyword | ||
+ | | ||
+ | * '' | ||
+ | * a Weertman type friction law | ||
+ | * '' | ||
+ | * '' | ||
+ | * '' | ||
+ | * a Coulomb type friction law | ||
+ | * '' | ||
+ | * '' | ||
+ | * '' | ||
+ | * '' | ||
+ | * '' | ||
+ | * '' | ||
+ | * '' | ||
+ | |||
+ | When < | ||
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SSA Mean Density = Real $rhoi | SSA Mean Density = Real $rhoi | ||
- | ! slip coeffs | + | ! Needed for Linear, Weertman and Coulomb |
- | SSA Slip Coefficient | + | ! Which law are we using (linear, weertman or coulomb) |
- | SSA Slip Coefficient 2 = Real 1.0e-3 | + | SSA Friction Law = String " |
+ | ! beta parameter (beta = 1/As^m) | ||
+ | SSA Friction Parameter | ||
+ | Real MATC "1.0e-3*(1.0 + sin(2.0*pi* tx(0) / L)*sin(2.0*pi* tx(1) / L)) | ||
+ | |||
+ | ! Needed for Weertman and Coulomb | ||
+ | ! Exponent m | ||
+ | SSA Friction Exponent | ||
+ | |||
+ | ! Min velocity for linearisation where ub=0 | ||
+ | SSA Friction Linear Velocity = Real 0.0001 | ||
+ | |||
+ | ! Needed for Coulomb only | ||
+ | ! post peak exponent in the Coulomb law (q, in Gagliardini et al., 2007) | ||
+ | SSA Friction Post-Peak = Real 1.0 | ||
+ | ! Iken's bound tau_b/N < C (see Gagliardini et al., 2007) | ||
+ | SSA Friction Maximum Value = Real 0.5 | ||
End | End | ||
</ | </ | ||
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==== Examples ==== | ==== Examples ==== | ||
- | For examples look in your elmer source distribution under [ELMER_TRUNK]/ | + | For examples look in your elmer source distribution under '' |