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Questions tagged [mesh]

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3
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0answers
49 views

Gmsh for 3D volume with inclusions

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 ...
4
votes
2answers
460 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? ...
4
votes
1answer
74 views

Convergence rate Jacobi/Gauss-Seidel with mesh resolution

In the book A Multigrid Tutorial - Briggs, Henson. McCormick in the beginning of Chapter 3, it is mentioned that ...because the convergence factor behaves as 1-$O(h^{2})$, the coarse grid ...
0
votes
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 ...
0
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1answer
54 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
1answer
163 views

Expanding Winding Number algorithm to arcs

I have a problem that I have been attempting to solve for a few days now. I was wondering if I would be able to get some assistance from the community. In order to detect if a point is in a polygon, ...
3
votes
1answer
91 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 ...
1
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0answers
73 views

Mesh error quantification using error norm for a sharp logistic function [closed]

Consider the following logistic function in 1D for the domain $0$ to $1$. $$ f(x) = \frac{1}{1 + \exp(-50(x-0.5))} $$ Let's say I resolve this on two meshes: first with 11 equispaced points (0.0, 0....
3
votes
1answer
91 views

Discontinuous Galerkin FEM : Control points are mid-points of edges instead of nodes

I am thinking to use discontinuous galerkin FEM (DGFEM) method to estimate discontinuous displacement field $u: \Omega \rightarrow \mathbb{R}^2$ at the crack surface of a material. The domain is ...
1
vote
1answer
313 views

Convert Unstructured Mesh to Structured

I have solved a simple problem on Openfoam, which is a 3D rectangular parallelopiped, filled with rectangular hexahedrons as mesh elements. The structured, mapped mesh was made in ICEM and solved in ...
1
vote
1answer
110 views

Barycentric interpolation equivalent for irregular hexahedra

I have a mesh with irregular hexaedra and I need a fast way to interpolate values at points inside these cells. I know that trilinear interpolation does not work well for large skews. Barycentric ...
1
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0answers
80 views

How to choose seed in flood/fill algorithm

I was able to draw to the outer airtight boundary of hole. Now I would like to implement interior flood/fill algorithm. To get an internal seed, only one method comes to my mind which is testing ...
1
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1answer
506 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?
1
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2answers
121 views

Sign of integer determinant 4 by 4

I'm in the context of this publication: http://www.gilbertbernstein.com/resources/booleans2009.pdf I applied quantization to my point coordinates: All coordinates are integer lying in [0, 2 power 20]....
1
vote
1answer
920 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 ...
1
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0answers
30 views

2D Test cases for overset meshes

I developed a parallel 2D overset mesh (chimera) assembler and I would like to test a large scale problem. I don't want to make up a test case myself but rather want something standard. Would you ...
9
votes
2answers
185 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 ...
1
vote
1answer
126 views

How to handle 2D and 3D models efficiently

My coworkers and I have developed a c++ library implementing a "3D Geological Model" class. Goal of this library is to provide a data structure that is used in computational codes (such as Finite ...
8
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2answers
337 views

Mesh ordering algorithms used by COMSOL Multiphysics

Ordering of elements in an unstructured mesh is undoubtedly very important for the performance of computations. For example, it determines the structure of sparse matrices arising from PDE ...
2
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2answers
377 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 ...
2
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0answers
75 views

Literature on numerical solving based on multiple meshes?

Consider solving a differential equation system for 1D, 2D, or 3D. It involves various input and output "field" variables, which, more often than not, correspond to various physical quantities ...
1
vote
1answer
3k views

Calculate Jacobian of triangular element given coordinates of vertices and displacements?

I am trying to determine quality of my mesh elements using the Jacobian determinant as the measure. My algorithm takes vertices of nodes in triangular mesh and moves them around so as to form ...
1
vote
2answers
200 views

Getting adjacent cells map for an unstructured polyhedral mesh

I am doing a little project on solving the heat equation using finite-volume method on a solid cube, I converted the polyhedral mesh of the cube to an OpenFOAM mesh. I have a Python code where I ...
1
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0answers
63 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 ...
2
votes
1answer
155 views

Coupling Boundary Condition of one PDE with source term of another PDE

We have a system of equations, wherein the BC of one PDE is coupled with the source term of another PDE. We have a regular 2D unit grid in x and y. There are two PDEs to be solved The first PDE (...
4
votes
4answers
324 views

How to “smoothen” (not just refine) a 2D/3D polygonal mesh

Suppose I have a complicated structure given in 2 or 3 dimensions as a polygon mesh. For example, this could represent a "cave" or an assembly of irreguar shaped particles or a tree, whatever. Now I'd ...
0
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0answers
69 views

FEM asynchronous assembly

I would like to implement nonlinear preconditioner along with nonlinear additive schwarz. I wonder if there is any scientific FEM package, which allows for asynchronous assembly? (I need assembly ...
4
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0answers
184 views

Once and for all: Which FEM plattform should I use for a very large multiphysics simulation?

I'm fooling around with the decision on how to build a multiphysics simulation for too long now (also several questions in this forum). First, I thought it would be possible/necessary to write most of ...
1
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4answers
272 views

Meshing: Handle an internal boundary

I ask this question because I do not see (m)any examples and I'd like to avoid to spend hours or days to work into a mesher only to see that it is impossible: Consider the sketch below. As you see, I ...
14
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6answers
3k views

What is a common file/data format for a mesh (for FEM)?

I'm developing an FEM simulation. For early testing, I will use simple self-written mesher and visualisation of the mesh graph. But I want to prepare my program to use data generated by an existing ...
1
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1answer
73 views

Common nodes in two FEM grids

There are two independent tetrahedral FEM grids. Second grid is subset of the first. By subset, I mean: nodes from the second grid are exactly in the same positions as some nodes from the first grid. ...
0
votes
1answer
621 views

what is the meaning of mesh smoothing steps in Gmsh?

In Gmsh mesh option list ,there is a smoothing concept, what does this mean and what is the effect of its number to the mesh quality?
0
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1answer
65 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 of ...
2
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1answer
107 views

How to project a 0 genus mesh model on a sphere?

I have a mesh which represents a 0-genus model. My goal is to construct a homeomorphism from that mesh to its bounding sphere. I'm trying to understand a paragraph in http://citeseerx.ist.psu.edu/...
2
votes
2answers
131 views

Find triangle which contains point on the sphere

Suppose I have a mesh of the sphere (points on the sphere and a triangulation). What is a good and efficient way to find the triangle which contains a point on the sphere (the point does not need ...
5
votes
1answer
165 views

Flux at coarse-fine mesh grid interface?

I am trying to solve one dimensional inviscid Burger's equation using adaptive mesh refinement. This is the PDE: $$\frac{\delta U}{\delta t} + \frac{\delta F}{\delta x} = 0$$ where the flux F of the ...
7
votes
1answer
2k views

Shrink wrapping algorithms to make a mesh watertight for 3d printing

I'm investigating algorithms to make a mesh watertight for 3d printing. I'd be very excited to implement such algorithms. The initial input is a mesh which is not watertight and I want to understand ...
4
votes
2answers
672 views

How to discretize Burger's equation?

I am trying to solve the very simple one dimensional burgers equation which is: $$\frac{\delta U}{\delta t} + \frac{\delta F}{\delta x} = 0$$ where the flux F of some variable U is defined as$$ F= \...
1
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0answers
96 views

Conservation at grid interface in adaptive mesh refinement

I am using adaptive mesh refinement to solve one dimensional inviscid Burgers equation. However I am facing some difficulty to handle grid interfaces which are not uniform (coarse-fine grid interface)....
0
votes
1answer
238 views

Adaptive mesh refinement basic conceptual problem

I am a beginner in adaptive mesh refinement (AMR). After I am done with the first two papers by Dr. Marsha Berger, I was trying to write my own code for a problem which has a parabolic partial ...
1
vote
1answer
96 views

alternatives to moving mesh technique

If one has to simulate oscillating plate/solid wall ( sinusoidal function of time) in a domain (a simple piston movement in 'y' direction), the obvious way would be scenario 1. For brevity, assume ...
2
votes
1answer
86 views

optimize vertices using a cost function on triangles

I want to optimize the vertex positions in a mesh, with a given cost function on the associated triangles. The paper gives a cost function, which evaluates to an real number by using a sum over the ...
3
votes
0answers
105 views

Creating FEM mesh for image region — what is the most suitable shape function?

I wish to create a FEM mesh to solve an inverse elasticity problem, for an irregular domain. This domain is given by a medical image, so it is discretised and each square on the grid has one scalar ...
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0answers
418 views

Equilateral triangle based mesh generation by intersection

In work I am currently working on I need to mesh some structure with equilateral triangles to study it using a kind of discrete element method known as spring networks or Lattice model. To mesh the ...
0
votes
2answers
293 views

Faster methods for projecting a mesh onto a hierachally unrelated mesh?

I have a set of independent meshes whose results I would like to project onto another non-hierachally related mesh. Until now, I've been accomplishing this by finding the nearest-distance node in the ...
0
votes
3answers
131 views

Meshing of polygons

I need to generate a sequence of increasingly denser high-quality triangular meshes for some pentagons in MATLAB. I want to supply as my input The coordinates of the 5 vertices of the pentagon ...
1
vote
1answer
765 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. ...
0
votes
1answer
940 views

What is Mesh Independence Report?

I am performing analysis on chassis (Static Structural) and for optimization purpose i am asked to generate MESH-INDEPENDENCE REPORT,of which i have no idea. I have tried going through research papers ...
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1answer
196 views

Conceptual question about fitting of scattered data

What are the problems that arise when fitting (2D or 3D) a set of scattered data? (non uniformly distributed) I had some data I had to fit and I solved the problem using the ...
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0answers
63 views

Data format for Cartesian mesh with cut cells

Is there a mesh data format which is particularly well suited for Cartesian meshes with Dey-Mittra style cut-cells? Ideally, one which does not require converting the cut-cells into a more general ...