# Pressure in solidDisplacementFoam

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 March 7, 2016, 15:44 Pressure in solidDisplacementFoam #1 Member   Ruggero Poletto Join Date: Nov 2013 Posts: 33 Rep Power: 5 Is it correct this in the D file: wall_name { type tractionDisplacement; traction uniform ( 0 0 0 ); pressure uniform 600000; value uniform (0 0 0); } Application of the pressure that act of a particular wall?

March 8, 2016, 06:52
#2
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Philip Cardiff
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Quote:
 Originally Posted by rupole1185 Is it correct this in the D file: wall_name { type tractionDisplacement; traction uniform ( 0 0 0 ); pressure uniform 600000; value uniform (0 0 0); } Application of the pressure that act of a particular wall?
Yes, this will apply a surface pressure of 0.6 MPa to the wall.
The surface pressure is: Tn = -n & (n & sigma),
where 'n' is the surface unit normals and 'sigma' is the stress tensor.

Philip

 March 8, 2016, 08:25 #3 Member   Ruggero Poletto Join Date: Nov 2013 Posts: 33 Rep Power: 5 Thanks a lot for your reply! __________________ ___________________________ President of CONSELF, the new CFD company with a great cloud solution. Try for free it here!

October 15, 2016, 15:48
tractionDisplacement | meaning of "value (0 0 0)"?
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Tom Dylan
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Quote:
 Originally Posted by bigphil Yes, this will apply a surface pressure of 0.6 MPa to the wall. The surface pressure is: Tn = -n & (n & sigma), where 'n' is the surface unit normals and 'sigma' is the stress tensor. Philip
Could you kindly explain the third parameter vector "value (0 0 0)"?

Does it have to do something with a pressure gradient?

My problem consists of pressure variations on a vertical (or inclined) wall in response to water level fluctuations. In that case the pressure has a hydrostatic vertical distribution. I am seeking the right boundary condition for such a case.

Any hints warmly appreciated!

Tom

October 15, 2016, 16:22
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Ruggero Poletto
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Quote:
 Originally Posted by tomdylan Could you kindly explain the third parameter vector "value (0 0 0)"? Does it have to do something with a pressure gradient? My problem consists of pressure variations on a vertical (or inclined) wall in response to water level fluctuations. In that case the pressure has a hydrostatic vertical distribution. I am seeking the right boundary condition for such a case. Any hints warmly appreciated! Tom
No the third term is just a common thing in openfoam. It's the variable value on the surface (I.e. the displacement is zero at first iteration)
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October 16, 2016, 17:26
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Philip Cardiff
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Quote:
 Originally Posted by rupole1185 No the third term is just a common thing in openfoam. It's the variable value on the surface (I.e. the displacement is zero at first iteration)
Hi Tom,

To add to the previous comment, I noticed from the other thread that you are interested in poro-elasticity; you should be careful to not to confuse the pore-pressure with the "pressure" in the solidTraction boundary condition, which is the normal component of the effective traction (or total traction depending on your particular implementation).

Philip

 October 26, 2016, 11:49 time varying tractionBC in response to hydrostatic fluctuations #7 New Member     Tom Dylan Join Date: May 2015 Posts: 18 Rep Power: 4 Dear Foamers, first, Philip, let me thank you again for your clarification on the difference between pore-pressure and pressure. to be honest I was at first sight a little bit confused but after a while I got things clear. Allow me to present some pictures to illustrate the analysis I am into right now. I want to apply a representative (in respect to the water level in the chamber) tractionBC on a vertical (or inclined) soil boundary patch. At the present I am not considering the rigid gravity wall structure of the ship lock, since I have not managed to deal with heterogeneity/multiregions. As you can figure out form the pictures the filling and emptying of the chamber (more the 6 m head difference) leads to a time varying hydrostatic pressure distribution along the horizontal sole and the chamber walls. At the bottom the traction BC is straight forward. However I am insecure as to how to represent a time varying traction BC at the vertical (or inclined) boundary patches resulting form a fluctuating hydrostatic pressure in the chamber. Interestingly, our groundwater measurements in a distance from the lock detected a clear and almost in-phase poroelastic response to the filling and emptying of the chamber in a range of up to 10 kN/m2 (yes the ground can react quite elastic). These head fluctuations are solely induced by stress variations in the chamber. I guess that I am not the first to deal with head fluctuations and their effect on solid traction and therefore suppose that a solution exists, but currently I have no clue for this kind of problem. Ana hints warmly appreciated! Tom

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