[GeoMechanicsApplication] Integrate the functionality for UPw interfaces by markelov208 · Pull Request #14266 · KratosMultiphysics/Kratos

markelov208 · 2026-03-09T14:06:22Z

📝 Description
A brief description of the PR.

Created integration tests that perform computations for:

column with a horizontal_interface
column with a vertical_interface
column with a horizontal_interface using diff_order_elements

The obtained solutions (displacement and pressure values) are compared with solutions obtained for

column
column using diff order elements.

Tests are Quasi-static and displacement, pressure and fluid flux are compared for all time steps.

Added PUCoupling , Permeability and FluidBodyFlow to UPwInterfaceElementContributions .

This requires allows to get proper values of pressure and fluid fluxes for these tests but it breaks two tests:

building_pit
test_interface_prestress
They have been fixed by adding "IGNORE_UNDRAINED" : true for interface material properties.

A hydraulic discharge flow field is disconnected at the horizontal interface because UPwInterfaceElement does not calculate the discharge now. Therefore a new issue [GeoMechanicsApplication] Add hydraulic discharge calculation in UPw interface element is created.

Fixed error with fluid_flux calculation in SmallStrainUPwDiffOrderElement::CalculateOnIntegrationPoints. A unit test is added.

markelov208 · 2026-03-10T12:20:01Z

Hi @WPK4FEM , @rfaasse and @avdg81 , I've added Permeability to UPwInterfaceElementContributions then building_pit and test_interface_presstress failed. Adding TRANSVERSAL_PERMEABILITY and DYNAMIC_VISCOSITY to MaterialParameters solves them. Is it acceptable?

WPK4FEM · 2026-03-10T13:06:17Z

Hi @WPK4FEM , @rfaasse and @avdg81 , I've added Permeability to UPwInterfaceElementContributions then building_pit and test_interface_presstress failed. Adding TRANSVERSAL_PERMEABILITY and DYNAMIC_VISCOSITY to MaterialParameters solves them. Is it acceptable?

Hi @markelov208, Yes I think that that is acceptable. Its what the water part of the U-Pw interface element needs.

rfaasse · 2026-03-10T14:26:47Z

Hi @WPK4FEM , @rfaasse and @avdg81 , I've added Permeability to UPwInterfaceElementContributions then building_pit and test_interface_presstress failed. Adding TRANSVERSAL_PERMEABILITY and DYNAMIC_VISCOSITY to MaterialParameters solves them. Is it acceptable?

In principle no problem for me. However, since we use IGNORE_UNDRAINED in most of the model, I would not expect this to be necessary. I think if you'd add IGNORE_UNDRAINED: true to the material parameters of the interface (instead of the transversal permeability and dynamic viscosity), it'll also work (and that might be a bit more intuitive, since the rest of the materials also have IGNORE_UNDRAINED set to true.

rfaasse · 2026-03-10T14:28:01Z

applications/GeoMechanicsApplication/tests/building_pit/linear_elastic/MaterialParameters.json

+                "MINIMUM_RELATIVE_PERMEABILITY" : 0.0001,
+                "TRANSVERSAL_PERMEABILITY"      : 5.0e-4,
+                "DYNAMIC_VISCOSITY"             : 1.0e-3


As mentioned in the other comment, I think this would also work:

Suggested change

"MINIMUM_RELATIVE_PERMEABILITY" : 0.0001,

"TRANSVERSAL_PERMEABILITY" : 5.0e-4,

"DYNAMIC_VISCOSITY" : 1.0e-3

"IGNORE_UNDRAINED" : true,

Because in that case, the contributions for permeability would be ignored by the interface element

Thank you for the suggestion! It works.

rfaasse

Hi Gennady, thank you for adding the integration tests for the interface! As mentioned the PR will likely change due to the fluid body flow etc, but these are my intermediate comments!

rfaasse · 2026-03-11T14:59:45Z

applications/GeoMechanicsApplication/tests/test_upw_interface.py

+            "WATER_PRESSURE", no_pressure_time, no_pressure_output, [5]
+        )[0]
+
+        self.assertGreater(baseline_top_pressure - no_pressure_top_pressure, 900.0)


What is the reason we use an assertGreater instead of assertAlmostEqual here?

The test has been generated by AI and I kept it just in case. Right now I removed it because it checks the imposed pressure. It should be somewhere for the tables/boundaries.

rfaasse · 2026-03-12T07:51:43Z

applications/GeoMechanicsApplication/tests/UPw_interface/README.md

+Displacement and water pressure values obtained with and without the interface are compared for all nodes. The following pairs are used:
+
+- `column_horizontal_interface` and `column`,
+- `column_vertical_interface` and `column`,
+- `column_horizontal_interface_diff_order_elements` and `column_diff_order_elements`.


If I understand correctly, this means we check that adding the interface does not have an effect on the results. That probably means we have high stiffnesses, such that the interfaces stay closed (correct me if I'm wrong).

I'm not sure, just asking, but would there be a benefit in having at least 1 test which does have an open interface (i.e. would it increase the covered paths within the element)?

You are right these tests show that the solution is the same with/without an interface and the interface stays rather thin. If stiffness values are lower then the interface gets thicker and a solution changes. It is not clear what to check in this case.

rfaasse · 2026-03-12T07:57:15Z

applications/GeoMechanicsApplication/tests/UPw_interface/column/column.mdpa

+Begin Table 1 X LINE_LOAD_Y
+    0.0000000000 -2000000.0000000000 
+    1.0000000000 -2000000.0000000000 
+End Table


I might be mistaken, but I don't see where this table is used in the parameters

Correct, one of many attempts to affect a solution. Removed.

rfaasse · 2026-03-12T07:59:50Z

applications/GeoMechanicsApplication/tests/UPw_interface/README.md

+
+Both same-order and diff-order element families are included. The figure below shows the column and constraints. The dashed line shows the position of the horizontal interface case.
+
+![Setup](setup.svg)


In the picture, it seems there is a line load at the top of the model. However, I don't see any line loads in the project params (only gravity loading). Is the picture correct?

The picture is corrected. Now there is a single arrow with P.

rfaasse · 2026-03-12T08:00:36Z

applications/GeoMechanicsApplication/geo_mechanics_application.h


 static const auto UPwInterfaceElementContributions =
-    std::vector{CalculationContribution::Stiffness, CalculationContribution::UPCoupling};
+    std::vector{CalculationContribution::Stiffness, CalculationContribution::UPCoupling,


I think Wijtze Pieter already mentioned this, but the FluidBodyFlow is still missing here.

Yes, FluidBodyFlow is added now and permeability and pressure acting on the top have been increased to have non-zero fluxes. the python script compares fluxes now.

rfaasse · 2026-03-12T09:31:29Z

applications/GeoMechanicsApplication/tests/UPw_interface/common/TwoMaterialParameters.json

+              "TRANSVERSAL_PERMEABILITY"   :  5.0e-4,
+              "DYNAMIC_VISCOSITY"          :  1.0e-3


Next to these two parameters, I think we also need info on the retention law, for example:

Suggested change

"TRANSVERSAL_PERMEABILITY" : 5.0e-4,

"DYNAMIC_VISCOSITY" : 1.0e-3

"TRANSVERSAL_PERMEABILITY" : 5.0e-4,

"DYNAMIC_VISCOSITY" : 1.0e-3

"RETENTION_LAW" : "SaturatedBelowPhreaticLevelLaw",

"SATURATED_SATURATION" : 1.0,

"RESIDUAL_SATURATION" : 1e-10,

"MINIMUM_RELATIVE_PERMEABILITY" : 0.0001,

See for example the building pit model: https://github.com/KratosMultiphysics/Kratos/blob/master/applications/GeoMechanicsApplication/tests/building_pit/linear_elastic/MaterialParameters.json#L268-L277

adding these parameters affects the solutions. I think by default all tests use SaturatedLaw retention law.

rfaasse · 2026-03-12T09:33:45Z

...ications/GeoMechanicsApplication/tests/UPw_interface/column_horizontal_interface/column.mdpa

+Begin Table 2 TIME WATER_PRESSURE
+    0.0000000000 0.0000000000
+    1.0000000000 1000.0000000000
+End Table


Since the water pressure is time dependent, does it make sense to add asserts for more time steps than just the latest ones?

Correct, now tests check parameters for all times steps.

rfaasse · 2026-03-12T09:34:48Z

applications/GeoMechanicsApplication/tests/UPw_interface/common/ProjectParameters_stage2.json

+        "max_line_search_iterations": 5,
+        "first_alpha_value": 0.5,
+        "second_alpha_value": 1.0,
+        "min_alpha": 0.1,
+        "max_alpha": 2.0,
+        "line_search_tolerance": 0.5,


I don't think these params are needed, since we don't use line search

Suggested change

"max_line_search_iterations": 5,

"first_alpha_value": 0.5,

"second_alpha_value": 1.0,

"min_alpha": 0.1,

"max_alpha": 2.0,

"line_search_tolerance": 0.5,

rfaasse · 2026-03-12T09:36:40Z

...s/GeoMechanicsApplication/tests/UPw_interface/common/ProjectParameters_interface_stage1.json

+                "kratos_module": "KratosMultiphysics.GeoMechanicsApplication",
+                "process_name": "ApplyK0ProcedureProcess",
+                "Parameters": {
+                    "model_part_name": "PorousDomain.settlement_computational_model_part"


Just to validate my understanding, this means it's the intention that K0 is done for the interfaces as well, right?

removed. Initially, the test was falling with Soil. Tried to find the reason.

rfaasse · 2026-03-12T09:37:54Z

applications/GeoMechanicsApplication/tests/UPw_interface/column_vertical_interface/column.mdpa

+
+Begin SubModelPart Top
+  Begin SubModelPartTables
+     1


Is the line load actually used? I don't see it in the project params, but I might have missed it

no, removed

markelov208

Hi Richard, many thanks for the review. It helped me to improve these tests and to learn better integration tests in general.

markelov208 · 2026-03-12T15:24:25Z

applications/GeoMechanicsApplication/tests/UPw_interface/column/column.mdpa

+Begin Table 1 X LINE_LOAD_Y
+    0.0000000000 -2000000.0000000000 
+    1.0000000000 -2000000.0000000000 
+End Table


Correct, one of many attempts to affect a solution. Removed.

markelov208 · 2026-03-12T15:24:51Z

applications/GeoMechanicsApplication/tests/test_upw_interface.py

+            "WATER_PRESSURE", no_pressure_time, no_pressure_output, [5]
+        )[0]
+
+        self.assertGreater(baseline_top_pressure - no_pressure_top_pressure, 900.0)


The test has been generated by AI and I kept it just in case. Right now I removed it because it checks the imposed pressure. It should be somewhere for the tables/boundaries.

markelov208 · 2026-03-12T15:37:06Z

applications/GeoMechanicsApplication/tests/UPw_interface/README.md

+
+Both same-order and diff-order element families are included. The figure below shows the column and constraints. The dashed line shows the position of the horizontal interface case.
+
+![Setup](setup.svg)


The picture is corrected. Now there is a single arrow with P.

markelov208 · 2026-03-12T15:40:14Z

applications/GeoMechanicsApplication/geo_mechanics_application.h


 static const auto UPwInterfaceElementContributions =
-    std::vector{CalculationContribution::Stiffness, CalculationContribution::UPCoupling};
+    std::vector{CalculationContribution::Stiffness, CalculationContribution::UPCoupling,


Yes, FluidBodyFlow is added now and permeability and pressure acting on the top have been increased to have non-zero fluxes. the python script compares fluxes now.

markelov208 · 2026-03-12T15:41:09Z

applications/GeoMechanicsApplication/tests/test_upw_interface.py

+        project_parameters_filenames = (
+            project_parameters_filenames or self.project_parameters_filenames
+        )
+        status = run_geo_settlement.run_stages(case_path, project_parameters_filenames)


Frankly speaking, I just grabbed something that I met first.

markelov208 · 2026-03-12T16:31:06Z

...s/GeoMechanicsApplication/tests/UPw_interface/common/ProjectParameters_interface_stage1.json

+                "kratos_module": "KratosMultiphysics.GeoMechanicsApplication",
+                "process_name": "ApplyK0ProcedureProcess",
+                "Parameters": {
+                    "model_part_name": "PorousDomain.settlement_computational_model_part"


removed. Initially, the test was falling with Soil. Tried to find the reason.

markelov208 · 2026-03-13T11:45:37Z

applications/GeoMechanicsApplication/tests/test_upw_interface.py

+    def test_horizontal_interface(self):
+        file_path = test_helper.get_file_path(os.path.join("UPw_interface", "column"))
+        output_data = self._run_two_stage_soil_case(file_path)
+        self.assertTrue(output_data.get("results"))
+
+    def test_horizontal_interface_diff_order(self):
+        file_path = test_helper.get_file_path(
+            os.path.join("UPw_interface", "column_diff_order_elements")
+        )
+        output_data = self._run_two_stage_soil_case(file_path)
+        self.assertTrue(output_data.get("results"))
+
+    def test_vertical_interface(self):
+        file_path = test_helper.get_file_path(
+            os.path.join("UPw_interface", "column_vertical_interface")
+        )
+        output_data = self._run_two_stage_interface_case(file_path)
+        self.assertTrue(output_data.get("results"))


Yes, these tests just run. Now removed them because these computations are also done in other tests.

markelov208 · 2026-03-13T11:54:22Z

applications/GeoMechanicsApplication/tests/test_upw_interface.py

+                    if pair not in seen_pairs:
+                        seen_pairs.add(pair)
+                        node_id_pairs.append(pair)
+
+        return node_id_pairs


a vertical interface consists of two elements and repeated pairs of nodes exist.

markelov208 · 2026-03-13T12:03:12Z

applications/GeoMechanicsApplication/tests/test_upw_interface.py

+            )
+        )
+
+        interface_nodes = self._read_mdpa_nodes(interface_mdpa_file_path)


corrected as well nodes_of_soil_model

markelov208 · 2026-03-13T12:06:11Z

...ications/GeoMechanicsApplication/tests/UPw_interface/column_horizontal_interface/column.mdpa

+Begin Table 2 TIME WATER_PRESSURE
+    0.0000000000 0.0000000000
+    1.0000000000 1000.0000000000
+End Table


Correct, now tests check parameters for all times steps.

added integration tests

2a8afc8

markelov208 self-assigned this Mar 9, 2026

markelov208 requested a review from a team as a code owner March 9, 2026 14:06

formatted with black

ea33682

markelov208 linked an issue Mar 9, 2026 that may be closed by this pull request

[GeoMechanicsApplication] Integrate the functionality for UPw interfaces #14042

Open

markelov208 added 6 commits March 9, 2026 17:07

Merge branch 'master' into geo/14042-integration-tests-for-UPw-interface

0c236f3

use small letters for test_UPw_interface.py

d1234f1

renamed class calls

cac24a3

added extra Material parameters

27e74d4

removed code smells

38a8548

added interface material parameters to building_pit

06a2f1b

markelov208 requested review from WPK4FEM, avdg81 and rfaasse March 10, 2026 12:17

rfaasse reviewed Mar 10, 2026

View reviewed changes

markelov208 added 2 commits March 10, 2026 21:15

used IGNORE_UNDRAINED true

3f0891a

Merge branch 'master' into geo/14042-integration-tests-for-UPw-interface

36c8284

rfaasse reviewed Mar 12, 2026

View reviewed changes

processed review comments

6cfc88b

markelov208 commented Mar 13, 2026

View reviewed changes

markelov208 requested a review from rfaasse March 13, 2026 12:57

markelov208 added 6 commits March 13, 2026 14:32

Merge branch 'master' into geo/14042-integration-tests-for-UPw-interface

905d1b1

fixed error with fluid_flux and added unit test

f8422f3

fixed code smells

5ee658d

added IGNORE_UNDRAINED true

98684ee

added checks

c9d9ef6

minor change

103bc92

markelov208 added 3 commits March 14, 2026 00:37

reverted checks

d7179d3

clang-format

ac5b9ec

reverted test_U_Pw_interface_element.cpp

c6669aa


		Both same-order and diff-order element families are included. The figure below shows the column and constraints. The dashed line shows the position of the horizontal interface case.

		![Setup](setup.svg)

		"TRANSVERSAL_PERMEABILITY" : 5.0e-4,
		"DYNAMIC_VISCOSITY" : 1.0e-3

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markelov208 commented Mar 9, 2026 •

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rfaasse commented Mar 10, 2026 •

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