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Usage of the Finite Element Method embedded in NDSolve and details on the implementation of the fem in mathematica.

6 votes
1 answer
239 views

How can I create higher order triangle elements when using NDSolve`FEM?

I'm using the Finite Element Method to solve an elasticity problem and i need to use a more precise element such as a nine node triangle. For my surprise when I run the code : Needs["NDSolve`FEM`"] m …
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  • 2,964
5 votes
2 answers
1k views

How to get the node id in a specific coordinate in a finite element mesh?

The following code generates a finite element mesh. Needs["NDSolve`FEM`"] order = 2; mesh = ToElementMesh[ImplicitRegion[300 < Sqrt[x x + y y], {x, y}], {{0, 1000}, {0, 1000}}, MaxCellMeasure -> 2000 …
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  • 2,964
4 votes
1 answer
189 views

Refinement problems

I have a hole in an infinite plate and a code that generates a finite element mesh of it. I need more elements concentrated near the hole, because the solution varies more at this region. The issue he …
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  • 2,964
3 votes
5 answers
335 views

Adapt a 9-node element routine to a 8-node

The function GenerateGridMesh[a_, b_, nx_, ny_] creates a grid of 9-node finite elements mesh. I need some help to adapt this routine to create 8 node element mesh. This function has as input data the …
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  • 2,964
4 votes
1 answer
548 views

Finite Elements 3D

Does anyone knows how to solve the Laplace equation in a Sphere domain and with the following boundary conditions: Consider alpha=0. I have tryed the following code, but i don't belive the boundary …
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  • 2,964
8 votes
3 answers
603 views

How to find ids in a curved line in a finite element mesh?

Previous discussion about this problem has already occurred in this link: How to get the node id in a specific coordinate in a finite element mesh? I have the following code that generates a finite …
Stratus's user avatar
  • 2,964
5 votes
1 answer
176 views

How to generate a GraphicsComplex using a quadratic approximation function?

The code below illustrates a finite element mesh composed by quadratic 9-node elemets. I'm using the GraphicsComplex and Polygon to plot the mesh, and I get a linear interpolation (see the figure). Ho …
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  • 2,964
4 votes
2 answers
289 views

Refine a quadrilateral mesh

I have created the following mesh for a slope stability problem: << NDSolve`FEM` coordinates = {{0., 0.}, {75, 0}, {75, 30}, {45, 30}, {35, 40}, {0, 40}, {14, 14}, {60, 14}, {26, 26}, {47 …
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  • 2,964
33 votes
7 answers
5k views

How to generate a mesh with quadrilateral elements?

I have the following code that generates a finite element mesh: Needs["NDSolve`FEM`"] order = 2; mesh = ToElementMesh[ DiscretizeGraphics[ GraphicsComplex[{{0, 4}, {5, 4}, {5, 0}, {8, 0}, {8, 8 …
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  • 2,964
8 votes
1 answer
257 views

Performance improvement: Finite Element Mesh graphics

I have created a Finite Elements mesh on GID (quadrilateral 9 nodes elements). I exported the nodes and the elements topology and i'm reading it from the following two text files: https://www.dropbox …
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  • 2,964
9 votes
1 answer
665 views

Help to create a 2D mesh generator (FEM)

I'm working in a finite element mesh generator. I built this function which generates an 8 node mesh (polynomials of order 2) without any interior node: (*Generate Grid Mesh of dimensions axb with …
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  • 2,964
1 vote
1 answer
135 views

Transient darcy flow equation

I can solve the following stationary Darcy problem: $div(\nabla u)=1$ with $ u = 0 \in \Gamma_d$ << NDSolve`FEM` x0 = 40; y0 = 30; r = 30; p = Polygon[{{0, 0}, {75, 0}, {75, 30}, {45, 30}, {35, 40}, …
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  • 2,964
2 votes
2 answers
144 views

How to interpolate and visualize a finite element integration point solution

I can intepolate the nodal solution using the function ufun = ElementMeshInterpolation[{mesh}, nodalsol] and visualize the nodal solution with the function SliceContourPlot3D[ufun[x, y, z], MeshRegion …
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  • 2,964
4 votes
2 answers
210 views

Solve Richards equation for unsaturated soils with FEM (`NDSolveValue`)

I am attempting to solve the nonlinear Richards equation for the dependent variable $\Psi(t,x,y)$. The equation is as follows: $\frac{\partial\theta(\Psi)}{\partial t}=\nabla. (k(\Psi)\nabla(\Psi + y) …
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  • 2,964