Adding buckling eigenvalue solver (#213)

* Adding geometric stiffness to shell elements

* Adding TACSBuckling API to cython wrapper

* Adding BucklingProblem class

* Adding buckling integration test

* clang format fixes

* loosening up shell test tol

* Adding buckling solver to mphys wrapper

* Minor mphys refactor

* Clang format fixes

* Reducing mesh size for mphys buckling test

* Increasing testflo CI timelimit

* Updating sigma value in eigenvalue test

* Adding rtol setting to ModalProblem setup

* Adding buckling example and benchmark

* Reducing N_PROCS to 1 for mphys buckling test

.github/workflows/unit_tests.yml

@@ -133,7 +133,7 @@ jobs:
           if [[ ${{ matrix.NAME }} == 'Real' ]]; then
             source ${TACS_DIR}/extern/ESP122/ESPenv.sh
           fi
-          testflo --timeout 120 .;
+          testflo --timeout 240 .;
       - name: Build docs
         run: |
           cd $TACS_DIR/docs;

docs/source/pytacs/buckling.rst

@@ -0,0 +1,19 @@
+BucklingProblem
+------------
+.. automodule:: tacs.problems.buckling
+
+Options
+^^^^^^^
+Options can be set for :class:`~tacs.problems.BucklingProblem` at time of creation for the class in the
+:meth:`pyTACS.createBucklingProblem <tacs.pytacs.pyTACS.createBucklingProblem>` method or using the
+:meth:`BucklingProblem.setOption <tacs.problems.BucklingProblem.setOption>` method. Current option values for a class
+instance can be printed out using the :meth:`BucklingProblem.printOption <tacs.problems.BucklingProblem.printOptions>` method.
+The following options, their default values and descriptions are listed below:
+
+.. program-output:: python -c "from tacs.problems import BucklingProblem; BucklingProblem.printDefaultOptions()"
+
+API Reference
+^^^^^^^^^^^^^
+.. autoclass:: tacs.problems.BucklingProblem
+  :members:
+  :inherited-members:

docs/source/pytacs/problems.rst

@@ -6,4 +6,5 @@ Problem classes
 
   static
   transient
-  modal
+  modal
+  buckling

examples/plate/benchmark/benchmark_buckle.py

@@ -0,0 +1,44 @@
+"""
+This script is used to regression test the example against historical values.
+"""
+
+import numpy as np
+import unittest
+import sys
+import os
+
+# Set the path to the example script we're testing
+example_path = os.path.join(os.path.dirname(__file__), "..")
+sys.path.append(example_path)
+
+# Reference values for eval functions
+FUNC_REF = {
+    "buckle_eigsb.0": 20.082400947865022,
+    "buckle_eigsb.1": 43.01440496545738,
+    "buckle_eigsb.2": 80.31233170890538,
+    "buckle_eigsb.3": 84.69751385025641,
+    "buckle_eigsb.4": 86.82024838978569,
+}
+
+
+class ExampleBenchmark(unittest.TestCase):
+    N_PROCS = 8  # this is how many MPI processes to use for this TestCase.
+
+    def setUp(self):
+        # Import the example to automatically run the script
+        import plate_buckle
+
+        self.example = plate_buckle
+
+    def benchmark_funcs(self):
+        """
+        Test the example eval functions against reference values
+        """
+        func_dict = self.example.funcs
+
+        # Test functions values against historical values
+        for func_name in func_dict:
+            with self.subTest(function=func_name):
+                np.testing.assert_allclose(
+                    func_dict[func_name], FUNC_REF[func_name], rtol=1e-6, atol=1e-6
+                )

examples/plate/plate_buckle.py

@@ -0,0 +1,50 @@
+"""
+This problem performs a buckling analysis on a 4m x 3m flat plate.
+The perimeter of the plate is pinned and loaded in compression (20kN/m) on its horizontal edges.
+We use TACS buckling eigenvalue solver through the pyTACS BucklingProblem interface.
+"""
+# ==============================================================================
+# Standard Python modules
+# ==============================================================================
+from __future__ import print_function
+import os
+
+# ==============================================================================
+# External Python modules
+# ==============================================================================
+from pprint import pprint
+
+import numpy as np
+from mpi4py import MPI
+
+# ==============================================================================
+# Extension modules
+# ==============================================================================
+from tacs import pyTACS
+
+comm = MPI.COMM_WORLD
+
+# Instantiate FEAAssembler
+bdfFile = os.path.join(os.path.dirname(__file__), "ss_plate_buckle.bdf")
+FEAAssembler = pyTACS(bdfFile, comm=comm)
+# Set up constitutive objects and elements
+FEAAssembler.initialize()
+
+# Setup static problem
+bucklingProb = FEAAssembler.createBucklingProblem(name="buckle", sigma=10.0, numEigs=5)
+bucklingProb.setOption("printLevel", 2)
+# Add Loads
+bucklingProb.addLoadFromBDF(loadID=1)
+
+# solve and evaluate functions/sensitivities
+funcs = {}
+funcsSens = {}
+bucklingProb.solve()
+bucklingProb.evalFunctions(funcs)
+bucklingProb.evalFunctionsSens(funcsSens)
+bucklingProb.writeSolution(outputDir=os.path.dirname(__file__))
+
+
+if comm.rank == 0:
+    pprint(funcs)
+    pprint(funcsSens)