USF_Sliding.f90
Sliding_Weertman
Flow Solution
in Flow Solution Name
, Normal Vector
The file USF_Sliding.f90
contains user functions to apply non-linear friction at the base of glacier.
The first user function (Sliding_Weertman
) is a non-linear Weertman-type friction law and is described in this page. The second user function (Friction_Coulomb
) is a non-linear water pressure dependant friction law, as proposed by Schoof (2005) and Gagliardini et al. (2007), and is presented here. The third user function (Sliding_Budd
) is described here and is from Budd et al 1984 (Annals of Glaciology 5, page 29-36).
The friction law in Weertman_Sliding
is of the form:
The Slip Coefficient in Elmer is then given as
When , in the previous equation is replaced by (linearisation for small velocity).
The parameters to be given are:
Weertman Friction Coefficient
→ Weertman Exponent
→ Weertman Linear Velocity
→ The required keywords in the SIF file for this user function are:
!!! Bedrock Boundary Condition Boundary Condition 1 Target Boundaries = 1 Normal-Tangential Velocity = Logical True Flow Force BC = Logical True Velocity 1 = Real 0.0 Slip Coefficient 2 = Variable Coordinate 1 Real Procedure "ElmerIceUSF" "Sliding_Weertman" Slip Coefficient 3 = Variable Coordinate 1 Real Procedure "ElmerIceUSF" "Sliding_Weertman" Weertman Friction Coefficient = Real 2.412579e-2 Weertman Exponent = Real $1.0/3.0 Weertman Linear Velocity = Real 0.00001 End
The Weertman friction law is used in the tests [ELMER_TRUNK]/elmerice/Tests/GL_MISMIP
and [ELMER_TRUNK]/elmerice/Tests/Contact
and especially tested in [ELMER_TRUNK]/elmerice/Tests/Friction_Weertman
.