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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3answers
515 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
2k views

Minimal surface solution in Python

Note: this question was also posted in StackOverflow and math.stackexchange. I have a set of 3D points defining a 3D contour, as shown below. The points in this contour lie in their best-fit plane ...
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1answer
39 views

stretch elliptic mesh to fit a circle

I've generated a 2D O-mesh around an airfoil. Unfortunately, the mesh O shape is not a perfect circle as you can see in the figure below (in the figure I plotted only the mesh nodes in blue). The red ...
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1answer
46 views

Gmsh meshes flat faces incorrectly for cylindrical faces

I have some C++ code that generates meshes from step files and then analyses these meshes for visibility of the faces from different viewing directions. I currently use CGAL but I would like to switch ...
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1answer
135 views

Is it possible to remesh with gmsh?

I am currently working on remeshers for my simulations (academic purpose) and I try to find a method to remesh previous meshes using Gmsh. The first mesh (normalMesh.msh) was created using a .geo file ...
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1answer
120 views

Single nodes after mpmetis partitioning

I was checking partitioning capabilities of Metis (mpmetis) when I noticed, that it leaves two single nodes. I have marked them in red Have you seen something similar or maybe it is my mistake? The ...
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0answers
44 views

Duplicate Surface Meshes in different Gmsh files

My objective is to get a conformal surface mesh between two geometries meshed independently in different files. By example, I can start with a simple cube in one .geo file and mesh this geometry. ...
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0answers
38 views

Isosurface extraction when you know the derivatives

I have a complicated equation that defines a shape in 3D, and I would like to generate a surface mesh. The shape is defined by an isosurface, i.e. the function is positive inside the shape and ...
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1answer
79 views

Comparing the following mesh grids for a star-shaped plate

Between these four different meshes for the same shape, compare them whilst considering the different results for displacement and stress. Moreover, the difference in computational cost and accuracy ...
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2answers
199 views

How many cells/elements do I need?

I'm relatively new in the CFD modelling and I'm making a VOF model of a rectangular box ($l \times w \times h = 120\times 80 \times8$ m) with an inlet ($w\times h = 10\times 8$) at the long side. ...
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1answer
2k 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
91 views

Is there any fundamental difference between meshing for FEM, FVM and FDM?

I am a novice to the field of computational science and have just started studying the FDM and FEM (haven't started on FVM yet). While trying the understand the subject I got this question and trying ...
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2answers
722 views

Creating 3D Mesh from stl files with gmsh

After long hours of searching for an answer I thought it might be better to ask the community. The problem I have is that I need to convert STL files to mesh files. I know that I therefore need to ...
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0answers
43 views

Metis: how to use and tutorial recommendation

I am new to METIS and trying to use it in my fortran code. I read the manual online. But still, I am not sure about how to implement it my code. I tried the test cases in the graphs directory. For ...
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1answer
49 views

Definition of Lagrange nodes in Gmsh

When gmsh uses higher-order tetrahedral elements, there is an underlying Lagrange basis used to specify the map from reference space to the element. I'm trying to load a gmsh mesh of 3rd degree ...
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1answer
349 views

Can TETGEN generate triangulation of a 2D point set?

I would like to link my Fortran 90 application to a library which would give me Delaunay triangulation (for a 2D set of points) and tetrahedralization (for a 3D set of points). As suggested in Fastest ...
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1answer
511 views

How can I coarsen a mesh in Gmsh when 'Mesh options' include 'Refine by splitting' but nothing about coarsening?

I am new to Gmsh and I am having trouble creating a circle with a coarse mesh. I use Geometry->Elementary entities->Add->Circle to create the geometry ...
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1answer
118 views

Load the mesh file with boundary marks

I'm want to load a mesh from a file, generated by triangle, and I want to use the boundary marks of its nodes (boundary marks of the file). It is possible? Also, I can change the mesh generator (or ...
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1answer
113 views

How to generate a face list from vertices?

I have a little background in writing toy finite volume CFD codes. In 2D Cartesian scenarios, I typically take $x_{\min}$, $x_{\max}$, $y_{\min}$, $y_{\max}$, and the number of points in $x$ and $y$ ...
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0answers
268 views

Gmsh for 3D volume with inclusions [closed]

In an attempt to create three-dimensional volumes with inclusions in Gmsh I stumble upon a problem which was non-existent in the two-dimensional case. I'm using the OpenCASCADE geometry kernel ...
3
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1answer
178 views

Is there any open-source code for a hybrid 2D mesh (triangles and quadrilaterals)?

The question is pretty much the title. Note that I have lots of experience using open-source meshing tool, e.g. Gmsh and OpenFoam blockMesh & snappyHexMesh. Nevertheless, I have no idea on how to ...
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2answers
395 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
258 views

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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7answers
927 views

Scripted Mesh Generation Software

I'm looking for a mesh generation software that is free and open source, provides a sane scripting interface for domain specification, works for complex geometries, can generate 2D and 3D meshes, ...
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2answers
508 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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1answer
193 views

Mesh generation with mostly the same elements (type/size..)

I'm searching for a way to generate a mesh that consists mostly of the same elements and i mean not only the same type, but the exact same size to ease the FEM-calculation. Is there a particular ...
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0answers
56 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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1answer
508 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
77 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
80 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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1answer
257 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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2answers
112 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
239 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
197 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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0answers
61 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
2k 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
775 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
2k 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
55 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
235 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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1answer
356 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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0answers
142 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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1answer
121 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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0answers
114 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 ...
2
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2answers
529 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 ...
11
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1answer
4k 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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2answers
797 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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0answers
94 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, ...
4
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1answer
340 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
144 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. ...