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userfunctions:coulomb [2014/01/07 08:44]
gag [SIF contents]
userfunctions:coulomb [2015/12/02 12:24] (current)
gag [General Description]
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   * **USF Fortran File:** ''​USF_Sliding.f90''​   * **USF Fortran File:** ''​USF_Sliding.f90''​
   * **USF Name:** ''​Friction_Coulomb''​   * **USF Name:** ''​Friction_Coulomb''​
-  * **Required Input Variable(s):​** A ''​Flow Solution''​ in ''​Flow Solution Name'',​ ''​Normal Vector'',​ ''​Stress''​+  * **Required Input Variable(s):​** A ''​Flow Solution''​ in ''​Flow Solution Name'',​ ''​Normal Vector'',​ ''​Stress'' ​or the ''​Effective Pressure''​ variable.
  
  
 ==== General Description ==== ==== General Description ====
-The file ''​USF_Sliding.f90''​ contains ​two user functions to apply non-linear friction at the base of glacier.  ​+The file ''​USF_Sliding.f90''​ contains ​three 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 [[:​userfunctions:​weertman|here]]. 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 in this page.+The first user function (''​Sliding_Weertman''​) is a non-linear Weertman-type friction law and is described [[:​userfunctions:​weertman|here]]. 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 in this page. The third user function (''​Sliding_Budd''​) is described [[:​userfunctions:​budd|here]] and is from Budd et al 1984 (Annals of Glaciology 5, page 29-36)
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   * ''​Friction Law Linear Velocity''​ -> <​m>​u_{t0}</​m>  ​   * ''​Friction Law Linear Velocity''​ -> <​m>​u_{t0}</​m>  ​
  
-The effective pressure is defined as <m>N = -sigma_{nn} -p_w</​m>, ​ where <​m>​sigma_{nn}</​m>​ is the normal Cauchy stress and <​m>​p_w</​m>​ the water pressure. ​Hereat time t+dt, the normal Cauchy stress is estimated from the stress computed at time t. The water pressure is prescribed as an ''​External Pressure''​ (Negative - Compressive convention, and therefore ​the water pressure is the opposite of the '​External Pressure'​). ​+The effective pressure is defined as <m>N = -sigma_{nn} -p_w</​m>, ​ where <​m>​sigma_{nn}</​m>​ is the normal Cauchy stress and <​m>​p_w</​m>​ the water pressure. ​If a variable ''​Effective Pressure''​ existsit is used to evaluate directly <​m>​N</​m>​. Else, the normal Cauchy stress is estimated from the stress computed at previous timestep. The water pressure is prescribed as an ''​External Pressure''​ (Negative - Compressive convention, and therefore '​External Pressure' ​should be equal to the opposite of the water pressure in the sif). 
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 ==== Examples ==== ==== Examples ====
-An example of the usage of the user function ​//​Friction_Coulomb// ​TODO +The Coulomb friction law is tested in ''​[ELMER_TRUNK]/elmerice/​Tests/​Friction_Coulomb''​ with a direct input of the effective pressure and ''​[ELMER_TRUNK]/elmerice/Tests/​Friction_Coulomb_Pw''​ with the effective pressure computed from the stress and a prescribed water pressure.  ​
  
  
userfunctions/coulomb.1389084247.txt.gz ยท Last modified: 2014/01/07 08:44 by gag
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