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solvers:ssa [2013/12/10 13:02]
gag [General Description] |
solvers:ssa [2014/04/10 14:54]
gag [General Description] |
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| ==== General Informations ==== | ==== General Informations ==== |
| :!: **Important changes have been made in ''SSABasalSolver''. This doc applies from Rev. 6472.** | :!: **Important changes have been made in ''SSABasalSolver''. This doc applies from Rev. 6480.** |
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| * **Solver Fortran File:** ''SSASolver.f90'' | * **Solver Fortran File:** ''SSASolver.f90'' |
| The ''Mean Density'' and ''Mean Viscosity'', if not uniform along the vertical direction, can be computed using the ''GetMeanValueSolver'' routine or the ''StucturedProjectToPlan'' solver (preferred solution). | The ''Mean Density'' and ''Mean Viscosity'', if not uniform along the vertical direction, can be computed using the ''GetMeanValueSolver'' routine or the ''StucturedProjectToPlan'' solver (preferred solution). |
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| 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 |
| ''Flow BodyForce 2'' for a SSA-1D problem or ''Flow BodyForce 3'' for a SSA-2D problem. | ''Flow BodyForce 2'' for a SSA-1D problem or ''Flow BodyForce 3'' for a SSA-2D problem. |
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| === Basal friction === | === Basal friction === |
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| Since version 6472, there are three friction laws implemented in the SSA solver: | Since version 6480, there are three friction laws implemented in the SSA solver: |
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| * a linear friction law | * a linear friction law |
| <m> tau_b = beta . u </m>\\ | <m> tau_b = beta . u </m>\\ |
| * a Weertman type friction law | * a Weertman type friction law |
| <m> tau_b = beta.{u_b}^{m - 1} . u_b </m>\\ | <m> tau_b = beta.{u_b}^{m - 1} . u </m>\\ |
| * a Coulomb type friction law | * a Coulomb type friction law |
| <m> tau_b = C.N {[{ {chi}/ {(1 + a . chi^q)} }]}^{1/n} . {u_b}^{1/n-1}. u_b </m>\\ | <m> tau_b = 1/{A_s}^{1/n} {[{ 1/ {(1 + alpha . chi^q)} }]}^{1/n} . {u_b}^{1/n-1}. u </m>\\ |
| where | where |
| <m> a = {(q - 1)^{q-1}}/{q^q} </m> | <m> alpha = {(q - 1)^{q-1}}/{q^q} </m> |
| and | and |
| <m> chi = {u_b}/{C^n N^n A_s} </m>\\ | <m> chi = {u_b}/{C^n N^n A_s} </m>\\ |
| * a Weertman type friction law | * a Weertman type friction law |
| * ''SSA Friction Parameter'' -> <m>beta</m> | * ''SSA Friction Parameter'' -> <m>beta</m> |
| | * ''SSA Friction Exponent'' -> <m>m</m> |
| | * ''SSA Friction Linear Velocity'' -> <m>u_{t0}</m> |
| * a Coulomb type friction law | * a Coulomb type friction law |
| * ''SSA Friction Parameter'' -> <m>beta</m> | * ''SSA Friction Parameter'' -> <m>beta= {A_s}^{-m}</m> |
| | * ''SSA Friction Exponent'' -> <m>m = 1/n</m> |
| | * ''SSA Friction Linear Velocity'' -> <m>u_{t0}</m> |
| | * ''SSA Friction Post-Peak'' -> <m>q >= 1</m> |
| | * ''SSA Friction Maximum Value'' -> <m>C</m> ~ max bed slope |
| | * ''Effective Pressure'' (variable) -> <m>N</m> |
| | * '' SSA Min Effective Pressure'' -> <m>N_{min}</m>, such that <m>N >= N_{min}</m> |
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| | When <m>u_b = (u^2+v^2)^{1/2}< u_{t0}</m>, <m>u_b</m> in the previous equations is replaced by <m>u_{t0}</m>. |
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| ==== Examples ==== | ==== Examples ==== |
| For examples look in your elmer source distribution under ''[ELMER_TRUNK]/elmerice/examples/Test_SSA''. | For examples look in your elmer source distribution under ''[ELMER_TRUNK]/elmerice/Tests/SSA'' and under ''[ELMER_TRUNK]/elmerice/examples/Test_SSA''. |
