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Questions tagged [mesh-generation]

The generation of a set of interconnected geometric objects that approximate a desired domain or region in euclidean space.

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Connectivity matrix in Finite Element Method in Triangular elements

Imagine a simple triangular base mesh in finite element method with an unknown number of elements (varying by the user). How can connectivity matrix be coded to be generated automatically?
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42 views

TetGen: Hole # in a facet does not have any coordinate

I am using a .poly file to generate a volume mesh using TetGen. My surface mesh has one hole and I have defined that in the .poly file. Every time I run TetGen it is giving me the following error "...
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48 views

Using gmsh python api for meshing a model with grouping elements by their volumes and surfaces

I am trying to use GMSH python api for creating 2d meshes of cad formats. I managed to write a script that can generate mesh successfully. However I need to know how elements are separated across ...
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2answers
452 views

3D contour mesh computation

I have the value of a function in three dimensions, $f(x, y, z)$, which varies smoothly. I would like to compute a 3D mesh where $f(x, y, z)$ has a particular value. Are there algorithms to do this? ...
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43 views

Efficient initial identification of solid or liquid domains for a block structured Cartesian grid generation system

INTRO Within the last 5 days I was able to generate a block structured Cartesian grid generation system with a combination of Fortran,C++ and Python. I am running intersection tests of the ...
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2answers
180 views

Unstructured mesh vs hybrid structured/unstructured for numerical simulations

While answering one of the questions on meshing process, I encountered a lack of understanding on my end for the comparison of the mesh quality. First, consider an unstructured mesh created in GMSH ...
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1answer
179 views

Creating a proper quad-mesh in GMSH for an “I”-shaped geometry

I'm trying to make a 2-D quad-only mesh of an "I"-shaped cross-section, with elements of size 5. So far I've managed to make it quad only, but some elements are very distorted when they shouldn't be. ...
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1answer
90 views

A difference running Gmsh in command line and in GUI for 3-D mesh generation [closed]

In Gmsh, I have a test.geo file. The question is: if I run gmsh -3 test.geo in the command line, I get the below error. ...
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1answer
73 views

Structural mechanics simulation using FLUENT compared to analytical solution

This is a continuation of my previous post, 1D analytical solution vs FEM solution for a bar under compression. For some reason, I cannot comment in it. The analytical solution to the 1-D static ...
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1answer
51 views

Gmsh exporting wrong mesh DATA [closed]

so hopefully I'll be using gmsh to make meshes out of 2-D cross sections with o thickness. I tried to make a structured mesh with quad elements of a rectangular ...
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2answers
107 views

Numerically solving a PDE on an unit tangent bundle

Let $M$ be a manifold and $UT(M)$ its unit tangent bundle. I have a PDE which looks something like $$ \frac{\partial f}{\partial t}(x,v) = (v\cdot \nabla_x) f(x,v) + \Delta f(x,v) $$ where $x\in M$, $...
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1answer
75 views

Compute mesh of the projection of a 3D surface triangulation

Given a triangulated surface in $\Bbb{R}^3$ we can simply project it on a plane. This will result in a family of triangles which do not form a mesh of the projection for the following reasons: each ...
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47 views

surface triangulation to boundary representation

Are there any open source tools available which can take a surface triangulation of mesh volumes and convert them to a boundary representation? I am interested in refining multiple region tetrahedral ...
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1answer
202 views

Resources on mesh generation for finite element methods

I know that this is not really apart of the rules as this is a recommendation question and these don't really have an answer per say. But, like this forum posting: https://stackoverflow.com/questions/...
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1answer
593 views

Custom Mesh Sizes in GMSH [closed]

I have a simple question today. I am new to GMSH and I am currently learning how to use the software program. I am using GMSH 3.0.4. What I am looking to do is to set a different mesh size for ...
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1answer
138 views

Create mesh for complicated 3D object for finite element analysis

I see images of steel connections, concrete dams, and other complicated 3D objects in papers which finite element analysis has been performed on them. My questions are: How these objects are created ...
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1answer
481 views

Algorithm to find boundary faces of mesh

I am given the data about nodes and elements of a tetrahedral mesh. What algorithm do I use to find the boundary faces of the mesh?
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1answer
799 views

Determinant of jacobian matrix

I am using an FEM code written in Fortran which I did not design. For a particular problem, the program complains that the determinant of the Jacobian matrix is inferior to zero. I vaguely ...
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0answers
50 views

adaptive / smart grid choice for dynamic programming

I've a read a paper about investing where they used a dynamic programming approach to solve a finite horizon problem, i.e. $$\max_{x_t} E[u(W_T)] $$ where $u$ is a utility function and $W_T$ ...
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2answers
183 views

Commonly-used metrics to quantify the irregularity of a triangular mesh

Say you have a triangular mesh on a flat plane. This has been drawn to eventually solve some problem in mechanics, for example. A mesh of equilateral triangles is the best inasmuch as the distances ...
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0answers
81 views

How to generate a tet10 mesh from a tet4 mesh

I am writing a FEN solver on tet10 elements. I right now have a CFD grid gen tool (Pointwise) which generates tet4 meshes. From this I have the element connectivity list and the node list. How do I go ...
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0answers
81 views

scalable parallel mesh/amr on unstructured grid

I am trying to code a scalable parallel AMR for unstructured grid. There seems to be three approaches for this a) Store some global grid info on each processor and partition with parmetis (The ...
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1answer
101 views

From edge-vertex connectivty to face-vertex connectivity?

I am working on mesh generation and optimization and encountered this problem. For example, in the figure below, we have the edge-vertex connectivity: 0-1 1-4 4-5 2-5 3-2 0-3 1-2 1-6 7-6 4-7 ...
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1answer
235 views

Global numbering of the vertices in a triangulation consisting of quadratic Lagrange elements

I've asked this question on Computational Science SE too. Consider the following triangulation of a rectangle $(0,a)\times(0,b)$: We have two types of triangles: I enumerate the rectangles(...
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2answers
341 views

Combined translational and rotational meshing in gmsh

For a flow simulation I am trying to reproduce a specific screw element design for an intermeshing co-rotating twin-screw extruder. I am using gmsh (v2.16) where the element is made from a 2D surface ...
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0answers
75 views

Generate discrete set of points in a feasible region

I have two vectors which specify the bounds $x_{min}$ and $x_{max}$ of the sample space. Also, it has to satisfy the linear constraint $Ax \leq b$. How to generate an evenly spaced set of points, ...
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2answers
418 views

2D mesh generator with geometric primitives

The question is exactly as the title: Which 2D (triangular) mesh generator software can be used which has a set of geometric primitives, controlled mesh size and standard output (.vtk or something ...
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1answer
214 views

Relationship between number of nodes, elements and sides in a triangular 2D mesh

Say that N is the number of nodes, E the number of elements and S the number of sides in a triangular 2D mesh. Is there a relationship that links these quantities, possibly taking into account that ...
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1answer
118 views

Meshing software: connectivity between elements and boundary

I am implementing an algorithm which produces a 4d mesh for a cylinder with a given 3d base. This means, I have a 3d mesh and I want to generate a 4d mesh for the corresponding space-time cylinder. ...
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1answer
266 views

Library for generating Discontinuous Galerkin FEM mesh

There are a number of packages available for generating Continuous Galerkin (CG) FEM meshes (gmsh, tetgen, netgen, etc.), but I have been unable to find one that generates Discontinuous Galerkin (DG) ...
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0answers
61 views

Mesh partitioner with user-defined overlap

I am looking for a mesh partitioner, where I can specify overlap, for example h = 3. I have looked into metis, but I wasn't able to find such a functionality. Is there any other package which ...
3
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1answer
425 views

Library for polygon processing in 3D

I need to process some polygons in 3D. They are typically loaded from an OFF or STL file. Then I need to do some transformations (rotation, move, resize), I'd like to check whether points are inside ...
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1answer
355 views

Two-dimensional mesh in fem: generating P1, P2, P3,… mesh from a P1 mesh

I have a two-dimensional mesh generated by triangle (the mesh generator software is not relevant). This software generates a perfect mesh for approximate the solution by piecewice linear functions (P1 ...
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27 views

Size of the support

I am working on moving least square approximation. To well-define of this method, the following matrix of size $n \times m$ must be of rank $m$. For $m=3$ $${\bf A }=\begin{pmatrix} 1&x_1&y_1\\...
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0answers
89 views

Finding boundary intersection points with Cartesian grid?

I would like to find the intersection points e.g. $M_x$ and $M_y$ as in the attached figure. The boundary (solid line) is defined by the Lagrangian points. I am working in C++ (basic - medium ...
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1answer
239 views

Mesh Generation in 1-D

I am using the method by Brandt in the FAS Multigrid algorithm to estimate the truncation error in a 1-D flow problem and then use that as the basis for generating a mesh(r-adaptation) in 1-D. The ...
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1answer
215 views

Does some form of documentation of GMSH exist?

I am looking to implement GMSh into a simualtor that I am going to create. I am looking to integrate the geo, mesh, and post processor modules. However, looking online, it appears the documentation ...
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492 views

Meshing two parts together [closed]

I have two parts, which need to be meshed. One part is located inside another. To simplify the problem, imagine two cubes: one inside another. Geometries are stored in STL files. From CAD point of ...
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1answer
3k views

What is a “hanging node” in the finite element meshing?

When reading literatures about finite element method, the term "hanging nodes" can often be encountered. Could anyone tell me what indeed is a hanging node?
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618 views

Quadtree type Grid

I would like to code for a quadtree type meshing but don't know how to do. If anyone can help or can share any starting code?
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1answer
654 views

Meshing options to generate number of the sides of and element (tetgen-triangle)

I wrote a finite element code in fortran 90. This code is really fast, except the meshing process. I used triangle and tetgen for meshing in 2D and 3D, respectively, so this process is fast, of ...
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1answer
949 views

Using Gmsh to create a mesh with zero thickness (quad) interface elements

I acknowledge the following post where a similar question is posed and a very nice answer has been provided: Is there a mesh generator that will generate zero thickness elements for interfaces? ...
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262 views

Adaptive Finite Element Method - Laplace

I'm currently attempting to turn my code for solving the laplace equation using finite element approximations into an adaptive one using the dual weighted residual as my error estimator: i.e. my ...
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2answers
408 views

structured to unstructured grid - calculating volume of cell

I have a 3-D structured grid that I am trying to convert over to an unstructured grid. Here is a picture of the 2-D structured grid with the nodes shown. It is axisymmetric about the x axis (y = 0). ...
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0answers
137 views

matplotlib contourplot for $\log z$ in the Complex Plane $\mathbb{C}$

I tried using Python's matplotlib on the logarithm and here is what I got, a kind of starburst pattern. Since the angle jumps between $\theta = 0$ and $\theta = 2\pi$, contour assumes there is a ...
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2answers
506 views

How to calculate efficiently mesh edges midpoints?

I have a 2D mesh of triangles used in Finite Element method to discretize the domain. I want to calculate the midpoints of all the edges because I want to use $\mathbb{P}^2$ elements. I am using ...
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0answers
379 views

Large meshing with tetgen

So I have a point cloud that I am creating a 3D flat rectangular surface from. I'm then turning it into a hollow box and connecting the corners by just dropping this surface mesh down. I need it to ...
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1answer
2k views

Triangular mesh of a 3D surface

I have an irregular grid of points describing this surface (a large subduction fault in South America). The color is depth. Anyway I have 3D coordinates (lon,lat,depth) at irregular intervals. I'm ...
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1answer
749 views

Tetrahedral Mesh file format in TETGEN

Ply file formats is used to represent mesh structures in the TETGEN freeware package. All the examples I've seen of 'ply' meshes were used for triangular meshes. ...
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4answers
2k views

Need a simple mesh format (for FEA) and a tool to generate the mesh

I want to write a 2D FEA code for my course project and I need to import a mesh (2d, simple quad/tri) on a simple geometry such as a L shaped plate or with a square/circular hole in it, something like ...