[GeoMechanicsApplication] Nodal extrapolation for interface elements by avdg81 · Pull Request #14061 · KratosMultiphysics/Kratos

avdg81 · 2025-12-11T15:56:41Z

📝 Description
Extended the nodal extrapolator such that it also supports interface elements (line and surface ones).

🆕 Changelog

The interface geometry can now return its mid-geometry through the member functions pGetGeometryPart and GetGeometryPart (the provided part index is not being used).
Since pGetGeometryPart returns a shared pointer to the underlying mid-geometry, the data member that keeps the mid-geometry also had to be changed to a shared pointer.
Added overrides for members GetGeometryFamily and GetGeometryOrderType for class template InterfaceGeometry, which forward the request to the underlying mid-geometry.
Any interface element can now return a list of its integration points (regardless of the adopted integration scheme).
Any interface element can now return its mid-geometry.
When calculating the linear extrapolation matrix, we now only need to provide it with the element itself rather than the element's geometry and integration method. This change enables us to define a unified API that works for all elements (recall that the integration method could not be easily extended towards ones that are commonly used by interface elements).
Added a utility function that returns the integration points of any element, including interface elements.
Added a utility function that calculates the determinants of the Jacobian matrices of any element, including interface elements.
Extended the nodal linear extrapolator such that it also supports any interface element.
Made a utility function that generates nodes public.
Added element setup functions that create linear and quadratic quadrilateral elements.
Extended several existing unit tests to cover the newly added overrides for interface geometry (i.e. getting the geometry's family as well as its order).
Added new unit tests to cover the proper construction of the mid-geometry of any interface geometry.
The unit tests of the linear nodal extrapolator have been updated such that they work with elements rather than geometries.
Added a helper function that checks whether two given lists of points are equal to within a provided tolerance on a pair-by-pair basis.
Reuse the UBlas utility functions to create expected matrices and vectors.

…nt rather than geometry, integration method and element ID

Also added utility functions for creating 2D 4-noded elements and 2D 8-noded elements. In addition, fixed the position of one node of the 20-noded hexahedron.

This way also works for interface elements.

…bian matrices at the integration points

Also removed a redundant template parameter.

Use the element family type as basis to decide which geometry to produce.

It returns the geometry family of the underlying mid-geometry.

It returns the order of the underlying mid-geometry.

The corresponding unit test covers a line interface element.

…-extrapolation-for-interface-elements and fixed merge conflicts

…i.s.o. streaming in results.

…-extrapolation-for-interface-elements and resolved merge conflicts

…tion-for-interface-elements

- Use `auto` when the type can be induced. - Made more variables `const`. - Moved some variables closer to their first usage. - Added a comment to explain why the extrapolation matrix of an interface element needs to expanded after calculating it from the mid-geometry. - Reformatted a few lines that are (deliberately) skipped by clang-format. - Renamed a variable to comply with the Kratos Style guide. - Eliminated a few intermediate variables. - Removed a redundant blank line.

…tion-for-interface-elements

…eometry Also added a helper function that checks whether to collections of points are equal within a given absolute tolerance.

…eometry

…e geometry

avdg81 · 2025-12-11T16:01:49Z

    }

-    std::unique_ptr<BaseType> mMidGeometry;
+    std::shared_ptr<BaseType> mMidGeometry;


Had to change this to std::shared_ptr since it is handed out now by pGetGeometryPart, which has this return type.

After changing the smart pointer type of `mMidGeometry`, I had forgotten to update the construction of the data member. Fixed that now.

rfaasse

Thank you for implementing well-tested and clear extrapolation functionality we need for visualizing results in the interfaces!

Also resolved an undesired dependency of the GeoMechanicsApplication core code on testing code. In addition, several Kratos expect macros have been replaced by GTest macros.

markelov208

Hi Anne, thank you very much for the changes. Now the tests looks like one. I have no blocking comments.

- The linear nodal extrapolator now only knows about geometry, and no longer about elements. The extrapolation utilities offer the entry point for calculating the extrapolation matrix for any kind of element, including interface elements. - Simplified expanding the extrapolation matrix for interface elements. - Defined the nodal positions in the test cases themselves to ease checking the expected values. - Added an offset to the positions of the nodes at the second side, to check whether the mid-side nodes are properly positioned between both sides. - Added a few clarifying comments.

- Renamed a data member to comply with the Kratos Style Guide.

…tion-for-interface-elements and fixed merge conflicts Also renamed a function parameter for consistency reasons.

…ints To avoid (too) many member functions for the interface elements, I have introduced a getter for the integration scheme. In turn, the integration scheme gives access to the number of integration points as well as the integration points themselves.

avdg81 · 2025-12-14T10:16:53Z

 #include "check_utilities.h"
 #include "geo_mechanics_application_variables.h"
 #include "includes/exception.h"
-#include "tests/cpp_tests/test_utilities.h"


This dependency of the GeoMechanicsApplication core code on the test code should never have been there. It has been removed now.

avdg81 · 2025-12-14T10:20:22Z

-Matrix ExtrapolationUtilities::CalculateExtrapolationMatrix(const Geometry<Node>& rGeometry,
-                                                            GeometryData::IntegrationMethod IntegrationMethod,
-                                                            size_t ElementId)
+Matrix ExtrapolationUtilities::CalculateExtrapolationMatrix(const Element& rElement)


This should now be the main entry point when we need to calculate the extrapolation matrix of an element (any element, including interface elements).

Also removed a few unused forward declarations.

markelov208

Hi Anne, thank you very much for processing the comments. From my view-point, the PR is ready to be merged. Lets wait for Richard's decision.

rfaasse

Thanks for processing the comments (the suggestion/discussion about restructuring took some work to implement)! In my opinion this is ready to go!

rfaasse · 2025-12-15T08:31:27Z

                CacheExtrapolationMatrixFor(
-                    rElement, mpExtrapolator->CalculateElementExtrapolationMatrix(
-                                  rElement.GetGeometry(), rElement.GetIntegrationMethod()));
+                    rElement, ExtrapolationUtilities::CalculateExtrapolationMatrix(rElement));


Looking at the code, I think it's indeed nice that we now put the responsibility of casting to an interface element in the utils. The only downside I see is that if we'd like to swap out the linear extrapolator to something else in the future, that's slightly more difficult (but still very easy to change, so in my opinion this is the best option now)

avdg81 and others added 30 commits November 28, 2025 15:00

ExtrapolationUtilities::CalculateNodalVectors now receives an eleme…

5aacd7c

…nt rather than geometry, integration method and element ID

Generating nodes has been made public

69f25f1

Let the unit test use elements rather than geometries

79d7dd8

Also added utility functions for creating 2D 4-noded elements and 2D 8-noded elements. In addition, fixed the position of one node of the 20-noded hexahedron.

When calculating the extrapolation matrix we now only require an element

8d06b40

Added a utility function to get the integration points of an element

a12021d

Use a more generic way of evaluating the shape function values

2a2f5c6

This way also works for interface elements.

Added a new utility function to evaluate the determinants of the Jaco…

a610c54

…bian matrices at the integration points

Removed a redundant function parameter

555ee76

Moved a declaration closer to its first usage

90067b8

Also removed a redundant template parameter.

Refactored creating the lower order geometry

ea362f7

Use the element family type as basis to decide which geometry to produce.

Implemented GetGeometryFamily for interface geometries

12e46f1

It returns the geometry family of the underlying mid-geometry.

Added a unit test for 4+4 noded interface geometry

6b1fb4b

Added a unit test for 8+8 noded interface geometry

109d2cf

Added creating lower order geometry of lines

738d5ee

Implemented GetGeometryOrderType for interface geometry

1c5cd8c

It returns the order of the underlying mid-geometry.

Removed unused variable

c9ac9d7

Can now calculate the extrapolation matrix of an interface element

5fb9886

The corresponding unit test covers a line interface element.

Made a member function private

b8b1dbf

Merge remote-tracking branch 'origin/master' into geo/experiment-with…

d4ea091

…-extrapolation-for-interface-elements and fixed merge conflicts

Added a comment that explains the use of an override

8559d0b

Added triangular and quadrilateral interface extrapolation test.

97912f2

Used ublasUtilities::CreateMatrix to setup expected result matrices, …

3e17ecc

…i.s.o. streaming in results.

Merge remote-tracking branch 'origin/master' into geo/experiment-with…

8511360

…-extrapolation-for-interface-elements and resolved merge conflicts

Merge remote-tracking branch 'origin/master' into geo/nodal-extrapola…

2234ade

…tion-for-interface-elements

Merge remote-tracking branch 'origin/master' into geo/nodal-extrapola…

a555d8b

…tion-for-interface-elements

Added a unit test to check the mid-geometry of a 2+2 line interface g…

ef20903

…eometry Also added a helper function that checks whether to collections of points are equal within a given absolute tolerance.

Added a unit test to check the mid-geometry of a 3+3 line interface g…

a3ec2a5

…eometry

Added a unit test to check the mid-geometry of a 3+3 surface interfac…

315e2ac

…e geometry

Added a unit test to check the mid-geometry of a 6+6 surface interfac…

7d256b1

…e geometry

avdg81 requested a review from a team as a code owner December 11, 2025 15:56

avdg81 added this to GeoMechanicsApplication (Deltares) Dec 11, 2025

avdg81 added the GeoMechanics Issues related to the GeoMechanicsApplication label Dec 11, 2025

avdg81 linked an issue Dec 11, 2025 that may be closed by this pull request

[GeoMechanicsApplication] Add support for line and interface elements when extrapolating results to nodes #14037

Closed

github-project-automation Bot moved this to In progress in GeoMechanicsApplication (Deltares) Dec 11, 2025

avdg81 commented Dec 11, 2025

View reviewed changes

rfaasse self-requested a review December 11, 2025 16:02

avdg81 commented Dec 11, 2025

View reviewed changes

Comment thread applications/GeoMechanicsApplication/tests/cpp_tests/test_utilities.h

Forgot to change std::make_unique to std::make_shared

6034e4a

After changing the smart pointer type of `mMidGeometry`, I had forgotten to update the construction of the data member. Fixed that now.

rfaasse reviewed Dec 12, 2025

View reviewed changes

Added a missing include

199fb0c

Also resolved an undesired dependency of the GeoMechanicsApplication core code on testing code. In addition, several Kratos expect macros have been replaced by GTest macros.

markelov208 reviewed Dec 12, 2025

View reviewed changes

avdg81 added 5 commits December 13, 2025 17:59

Processed Gennady's review suggestions

90281a5

- Renamed a data member to comply with the Kratos Style Guide.

Merge remote-tracking branch 'origin/master' into geo/nodal-extrapola…

f35637f

…tion-for-interface-elements and fixed merge conflicts Also renamed a function parameter for consistency reasons.

Renamed another data member to comply with the Kratos Style Guide

9383ba6

avdg81 commented Dec 14, 2025

View reviewed changes

avdg81 added 3 commits December 14, 2025 11:55

Updated some #include lists

3d74866

Also removed a few unused forward declarations.

Cleaned up another #include list

0793346

Cleaned up yet another #include list

1164b5c

avdg81 requested review from markelov208 and rfaasse December 14, 2025 11:17

markelov208 approved these changes Dec 15, 2025

View reviewed changes

github-project-automation Bot moved this from In progress to Reviewer approved in GeoMechanicsApplication (Deltares) Dec 15, 2025

rfaasse approved these changes Dec 15, 2025

View reviewed changes

avdg81 merged commit 06d5fdb into master Dec 15, 2025
9 of 10 checks passed

avdg81 deleted the geo/nodal-extrapolation-for-interface-elements branch December 15, 2025 09:01

github-project-automation Bot moved this from Reviewer approved to Done in GeoMechanicsApplication (Deltares) Dec 15, 2025

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