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userfunctions:coulomb [2015/11/26 15:44] gag [General Description] |
userfunctions:coulomb [2015/12/02 12:24] (current) gag [General Description] |
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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. Here, at 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'' exists, it 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. |