Questions tagged [mesh-generation]
The generation of a set of interconnected geometric objects that approximate a desired domain or region in euclidean space.
114
questions
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38 views
Surface mesh from labeled 3D points
I'm trying to figure out how to create a surface mesh from a set of labeled 3D points. The 3D object could be something like part of a cave system or asteroid where there would be parts of the surface ...
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1answer
93 views
Partial differential equation FEM application
I have a PDE which looks like Helmholtz wave equation on one dimensional domain.
$$\dfrac{d^2u(x)}{dx^2}+\pi^2u(x)=f(x)$$
where $-\infty <x<\infty $
Also, $f(x)= 1$ for $-0.25<x<0.25$, I ...
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0answers
28 views
Determining the voxels between two boundary surfaces
I am working on human brain tACS simulations where I have the models of the skin, skull, csf, brain and ventricles in STL format. The shape does not matter and there are no intersections. I want to ...
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0answers
18 views
Adding a boundary surface on a STL model in Gmsh
Background info
I want to run brain simulations with models from the PHM repository (not relevant to the problem but suits the narrative) which are shipped in STL format. The meshes of the STL have ...
2
votes
1answer
61 views
Mesh partition quality
I am working on static FE mesh partitioning and in order to achieve a good quality partitioning I want to know how to drecrease interprocessor communication by increasing the connectivity of elements ...
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1answer
43 views
Why addCylinder function not respecting the given coordinates?
I tried to generate 3 very simple cylinders, each other connected to it end, however the cylinder get connected to an unexistent point in space as the image shows:
It was supposed to each segment be ...
0
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1answer
105 views
Gmsh for .inp file
How do I get an .inp file from Gmsh? I need to create a simple geometry and mesh it and define the boundary conditions in Gmsh and export it as an ...
0
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1answer
61 views
Creating a mesh around an 1-D line to form a 2-D object
Given the following code, how can I perform a mesh generation around the line, to make a 2D form in GMSH API? Extrude or Mirror ...
3
votes
2answers
182 views
Minimum number of elements (mesh size) for electromagnetic simulation
Does someone have a reference for the minimum number of elements (or maximum mesh size) for electromagnetic simulations where a mathematical or numerical explanation is given?
I have found several ...
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2answers
80 views
What are the alternatives for ABAQUS in generating an *.inp file from a CAD model
ABAQUS gives a .inp file (in pre-processing stage) where the information with regard to the preprocessed model is defined, information such as geometry, mesh type, number of elements, boundary ...
3
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2answers
165 views
Why FVM can handle unstructured meshes while FDM cannot?
How come Finite Volume Method(FVM) handle the unstructured meshes and Finite difference Method cannot, whereas in FVM to approximate the fluxes at the boundary we use the central differencing?
My ...
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2answers
84 views
How to find out the difference between a structured and unstructured mesh using the file containing the mesh information?
I have two different mesh files (both are .inp files obtained from Abaqus) that represent the exact same geometries with the same boundary conditions, etc. The only difference is that one of them is ...
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1answer
46 views
Filling a volume with generalised polyhedra
Given a volume (say, some polyhedron), I need to fill it with smaller polyhedra, such that the space is filled as much as possible. The constraints and relaxations are:
(0) For a computation ...
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1answer
44 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 ...
2
votes
1answer
80 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 ...
3
votes
1answer
481 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 ...
2
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0answers
39 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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0answers
100 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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1answer
161 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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0answers
69 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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2answers
2k 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 ...
4
votes
1answer
61 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
909 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 ...
0
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1answer
189 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 ...
1
vote
1answer
220 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 $y$ ...
3
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0answers
472 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
votes
1answer
250 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 ...
0
votes
1answer
589 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?
4
votes
2answers
536 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? ...
1
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0answers
57 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 ...
5
votes
2answers
481 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 ...
2
votes
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
710 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 ...
0
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1answer
99 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 ...
4
votes
2answers
113 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 $x\in M$, $...
3
votes
1answer
239 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
64 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 ...
9
votes
1answer
261 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/...
3
votes
1answer
3k 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 ...
1
vote
3answers
720 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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vote
1answer
907 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
58 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 $W_T$ ...
9
votes
2answers
301 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
170 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
119 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 ...
0
votes
1answer
128 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
411 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(...
2
votes
2answers
589 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 ...
