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problems:rheology [2013/01/21 10:33] rgladstone |
problems:rheology [2021/07/12 07:06] (current) gagliar [Glen's flow law] |
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==== Glen's flow law ==== | ==== Glen's flow law ==== | ||
- | This is a SIF entry for Glen's flow law (after: Paterson, | + | This is a SIF entry for Glen's flow law (after: |
< | < | ||
- | ! Glen's flow law (using Glen) | + | ! Define some constant at the top of the SIF file (using LUA) |
- | !---------------- | + | ! Define the parameter in MPa - a - m |
- | ! viscosity stuff | + | #yearinsec = 365.25*24*60*60 |
- | !---------------- | + | #rhoi = 900.0/ |
- | Viscosity Model = String "Glen" | + | #rhow = 1000.0/ |
- | ! Viscosity has to be set to a dummy value | + | #gravity = -9.81*yearinsec^2 |
- | ! to avoid warning output from Elmer | + | |
- | Viscosity = Real 1.0 | + | ! Prefactor from Cuffey and Paterson (2010) in MPa^{-3} a^{-1} |
+ | #A1 = 2.89165e-13*yearinsec*1.0e18 | ||
+ | #A2 = 2.42736e-02*yearinsec*1.0e18 | ||
+ | #Q1 = 60.0e3 | ||
+ | #Q2 = 115.0e3 | ||
+ | |||
+ | |||
+ | Material 1 | ||
+ | Density = Real #rhoi | ||
+ | |||
+ | | ||
+ | !---------------- | ||
+ | ! viscosity stuff | ||
+ | !---------------- | ||
+ | |||
+ | Viscosity Model = String "glen" | ||
+ | Viscosity = 1.0 ! Dummy but avoid warning output | ||
Glen Exponent = Real 3.0 | Glen Exponent = Real 3.0 | ||
- | Critical Shear Rate = Real 1.0e-10 | + | |
- | ! Rate factors (Paterson value in MPa^-3a^-1) | + | |
- | Rate Factor 1 = Real 1.258e13 | + | |
- | Rate Factor 2 = Real 6.046e28 | + | |
- | ! these are in SI units - no problem, as long as | + | |
- | ! the gas constant also is | + | |
- | Activation Energy 1 = Real 60e3 | + | |
- | Activation Energy 2 = Real 139e3 | + | |
- | Glen Enhancement Factor = Real 1.0 | + | |
- | ! the variable taken to evaluate the Arrhenius law | + | |
- | ! in general this should be the temperature relative | + | |
- | ! to pressure melting point. The suggestion below plugs | + | |
- | ! in the correct value obtained with TemperateIceSolver | + | |
- | Temperature Field Variable = String "Temp Homologous" | + | |
- | ! the temperature to switch between the | + | |
- | ! two regimes in the flow law | + | |
Limit Temperature = Real -10.0 | Limit Temperature = Real -10.0 | ||
- | ! In case there is no temperature variable | + | Rate Factor 1 = Real #A1 |
- | | + | Rate Factor 2 = Real #A2 |
+ | Activation Energy 1 = Real #Q1 | ||
+ | Activation Energy 2 = Real #Q2 | ||
+ | Glen Enhancement Factor = Real 1.0 | ||
+ | Critical Shear Rate = Real 1.0e-10 | ||
+ | |||
+ | Constant Temperature = Real -1.0 | ||
+ | End | ||
</ | </ | ||
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This Material section gives the law with a fixed rate factor: | This Material section gives the law with a fixed rate factor: | ||
< | < | ||
+ | Material 1 | ||
! Glen's flow law (using Glen) | ! Glen's flow law (using Glen) | ||
!----------------- | !----------------- | ||
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Arrhenius Factor = Real $1.0E-16 * 1.0E18 | Arrhenius Factor = Real $1.0E-16 * 1.0E18 | ||
Glen Enhancement Factor = Real 1.0 | Glen Enhancement Factor = Real 1.0 | ||
+ | End | ||
</ | </ | ||
- | This is a SIF entry for Glen's flow law (after: Paterson, W. S. B. 1994. '' | + | This is a SIF entry for Glen's flow law (after: Paterson, W. S. B. 1994. '' |
< | < | ||
!! Glen's flow law (using power law) | !! Glen's flow law (using power law) | ||
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- | An example using Glen's flow law can be downloaded {{: | + | An example using Glen's flow law can be found in '' |
==== Anisotropic Ice ==== | ==== Anisotropic Ice ==== | ||
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The rheology of **porous ice**, namely firn and snow, is represented using the porous law proposed by Gagliardini and Meyssonnier (1997). This law is implemented in Elmer/Ice in the [[solvers: | The rheology of **porous ice**, namely firn and snow, is represented using the porous law proposed by Gagliardini and Meyssonnier (1997). This law is implemented in Elmer/Ice in the [[solvers: | ||
+ | ==== Damage ==== | ||
+ | Damage is accounted for through the enhancement factor. Damage evolution is modelled following the approach in Krug et al. (2014). More information can be found [[userfunctions: |