public void WriteMesh()
{
if (writeFieldsNext)
{
throw new InvalidOperationException("A mesh has already been written.");
}
// Nodes
writer.WriteLine("DATASET UNSTRUCTURED_GRID");
writer.WriteLine(String.Format("POINTS {0} double", mesh.VtkPoints.Count));
for (int i = 0; i < mesh.VtkPoints.Count; ++i) // Their indices in Model.Nodes are equal to their IDs
{
VtkPoint point = mesh.VtkPoints[i];
writer.Write(String.Format("{0} {1} 0.0\n", point.X, point.Y));
}
// Element connectivity
int elementDataCount = 0;
foreach (VtkCell cell in mesh.VtkCells)
{
elementDataCount += 1 + cell.Vertices.Count;
}
writer.WriteLine(String.Format("\nCELLS {0} {1}", mesh.VtkCells.Count, elementDataCount));
foreach (VtkCell cell in mesh.VtkCells)
{
writer.Write(cell.Vertices.Count);
foreach (VtkPoint point in cell.Vertices)
{
writer.Write(' ');
writer.Write(point.ID);
}
writer.WriteLine();
}
// Element types
writer.WriteLine("\nCELL_TYPES " + mesh.VtkCells.Count);
foreach (VtkCell cell in mesh.VtkCells)
{
writer.WriteLine(cell.Code);
}
}
public void WriteOutputData(IDofOrderer dofOrderer, Vector freeDisplacements, Vector constrainedDisplacements, int step)
{
// TODO: guess initial capacities from previous steps or from the model
var allPoints = new List <VtkPoint>();
var allCells = new List <VtkCell>();
var displacements = new List <double[]>();
var strains = new List <Tensor2D>();
var stresses = new List <Tensor2D>();
int pointCounter = 0;
foreach (XContinuumElement2D element in model.Elements)
{
Vector standardDisplacements = dofOrderer.ExtractDisplacementVectorOfElementFromGlobal(element,
freeDisplacements, constrainedDisplacements);
Vector enrichedDisplacements =
dofOrderer.ExtractEnrichedDisplacementsOfElementFromGlobal(element, freeDisplacements);
bool mustTriangulate = MustBeTriangulated(element, out ISingleCrack intersectingCrack);
if (!mustTriangulate)
{
// Mesh
var cellPoints = new VtkPoint[element.Nodes.Count];
for (int p = 0; p < cellPoints.Length; ++p)
{
cellPoints[p] = new VtkPoint(pointCounter++, element.Nodes[p]);
allPoints.Add(cellPoints[p]);
}
allCells.Add(new VtkCell(element.CellType, cellPoints));
// Displacements
for (int p = 0; p < cellPoints.Length; ++p)
{
displacements.Add(new double[] { standardDisplacements[2 * p], standardDisplacements[2 * p + 1] });
}
// Strains and stresses at Gauss points of element
// WARNING: do not use the quadrature object, since GPs are sorted differently.
IReadOnlyList <GaussPoint> gaussPoints = element.GaussPointExtrapolation.Quadrature.IntegrationPoints;
var strainsAtGPs = new Tensor2D[gaussPoints.Count];
var stressesAtGPs = new Tensor2D[gaussPoints.Count];
for (int gp = 0; gp < gaussPoints.Count; ++gp)
{
EvalInterpolation2D evalInterpol =
element.Interpolation.EvaluateAllAt(element.Nodes, gaussPoints[gp]);
(Tensor2D strain, Tensor2D stress) = ComputeStrainStress(element, gaussPoints[gp],
evalInterpol, standardDisplacements, enrichedDisplacements);
strainsAtGPs[gp] = strain;
stressesAtGPs[gp] = stress;
}
// Extrapolate strains and stresses to element nodes. This is exact, since the element is not enriched
IReadOnlyList <Tensor2D> strainsAtNodes = element.GaussPointExtrapolation.
ExtrapolateTensorFromGaussPointsToNodes(strainsAtGPs, element.Interpolation);
IReadOnlyList <Tensor2D> stressesAtNodes = element.GaussPointExtrapolation.
ExtrapolateTensorFromGaussPointsToNodes(stressesAtGPs, element.Interpolation);
for (int p = 0; p < cellPoints.Length; ++p)
{
strains.Add(strainsAtNodes[p]);
stresses.Add(stressesAtNodes[p]);
}
}
else
{
// Triangulate and then operate on each triangle
SortedSet <CartesianPoint> triangleVertices = intersectingCrack.FindTriangleVertices(element);
IReadOnlyList <Triangle2D <CartesianPoint> > triangles = triangulator.CreateMesh(triangleVertices);
foreach (Triangle2D <CartesianPoint> triangle in triangles)
{
// Mesh
int numTriangleNodes = 3;
var cellPoints = new VtkPoint[numTriangleNodes];
for (int p = 0; p < numTriangleNodes; ++p)
{
CartesianPoint point = triangle.Vertices[p];
cellPoints[p] = new VtkPoint(pointCounter++, point.X, point.Y, point.Z);
allPoints.Add(cellPoints[p]);
}
allCells.Add(new VtkCell(CellType.Tri3, cellPoints));
// Displacements, strains and stresses are not defined on the crack, thus they must be evaluated at GPs
// and extrapolated to each point of interest. However how should I choose the Gauss points? Here I take
// the Gauss points of the subtriangles.
IGaussPointExtrapolation2D extrapolation = ExtrapolationGaussTriangular3Points.UniqueInstance;
IIsoparametricInterpolation2D interpolation = InterpolationTri3.UniqueInstance;
// Find the Gauss points of the triangle in the natural system of the element
IInverseInterpolation2D inverseMapping = element.Interpolation.CreateInverseMappingFor(element.Nodes);
var triangleNodesNatural = new NaturalPoint[numTriangleNodes];
for (int p = 0; p < numTriangleNodes; ++p)
{
triangleNodesNatural[p] = inverseMapping.TransformPointCartesianToNatural(cellPoints[p]);
}
NaturalPoint[] triangleGPsNatural =
FindTriangleGPsNatural(triangleNodesNatural, extrapolation.Quadrature.IntegrationPoints);
// Find the field values at the Gauss points of the triangle (their coordinates are in the natural
// system of the element)
var displacementsAtGPs = new double[triangleGPsNatural.Length][];
var strainsAtGPs = new Tensor2D[triangleGPsNatural.Length];
var stressesAtGPs = new Tensor2D[triangleGPsNatural.Length];
for (int gp = 0; gp < triangleGPsNatural.Length; ++gp)
{
EvalInterpolation2D evalInterpol =
element.Interpolation.EvaluateAllAt(element.Nodes, triangleGPsNatural[gp]);
displacementsAtGPs[gp] = element.CalculateDisplacementField(triangleGPsNatural[gp],
evalInterpol, standardDisplacements, enrichedDisplacements).CopyToArray();
(Tensor2D strain, Tensor2D stress) = ComputeStrainStress(element, triangleGPsNatural[gp],
evalInterpol, standardDisplacements, enrichedDisplacements);
strainsAtGPs[gp] = strain;
stressesAtGPs[gp] = stress;
}
// Extrapolate the field values to the triangle nodes. We need their coordinates in the auxiliary
// system of the triangle. We could use the inverse interpolation of the triangle to map the natural
// (element local) coordinates of the nodes to the auxiliary system of the triangle. Fortunately they
// can be accessed by the extrapolation object directly.
IReadOnlyList <double[]> displacementsAtTriangleNodes =
extrapolation.ExtrapolateVectorFromGaussPointsToNodes(displacementsAtGPs, interpolation);
IReadOnlyList <Tensor2D> strainsAtTriangleNodes =
extrapolation.ExtrapolateTensorFromGaussPointsToNodes(strainsAtGPs, interpolation);
IReadOnlyList <Tensor2D> stressesAtTriangleNodes =
extrapolation.ExtrapolateTensorFromGaussPointsToNodes(stressesAtGPs, interpolation);
for (int p = 0; p < numTriangleNodes; ++p)
{
displacements.Add(displacementsAtTriangleNodes[p]);
strains.Add(strainsAtTriangleNodes[p]);
stresses.Add(stressesAtTriangleNodes[p]);
}
}
}
}
using (var writer = new VtkFileWriter($"{pathNoExtension}_{step}.vtk"))
{
writer.WriteMesh(allPoints, allCells);
writer.WriteVector2DField("displacement", displacements);
writer.WriteTensor2DField("strain", strains);
writer.WriteTensor2DField("stress", stresses);
}
}
