Questions tagged [mesh]

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52 views

How to determine the orientation of convex/concave hexahedra?

I am writing a code that checks the orientation of a list of vertices (along with face connectivity) describing both convex and concave hexahedra. The face connectivity table stores the list of vertex ...
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2answers
309 views

Is mesh orthogonality important for FEM?

While studying mesh quality metrics in literature and software documentation, I've seen discussions about mesh orthogonality in Finite Volume Method (FVM) contexts, but not for Finite Element Method (...
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1answer
81 views

Renumbering the nodes for quadratic basis functions for a 2D domain

I have a simple triangulation for a 2D domain, described by the connectivity matrix $T$ and by the point matrix $P$. For didactic purposes, I assembled the stiffness matrix for $-\Delta u = f$ by ...
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1answer
88 views

Visualize a mesh from list of 3D point and faces

I have a list of vertices and faces. Now, I want to create a mesh using the given points and faces list and visualize it. Also, I want to play with the mesh by adding an extra point on the faces. Can ...
5
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1answer
142 views

Solving PDEs in parallel

I have read different approaches on how to solve pdes in parallel which are discretized using finite element method. For example: Non-overlapping domain decomposition approach as mentioned in https://...
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0answers
119 views

Open-source Hexahedral meshing tools

I'm looking for an open-source automatic meshing tool or library able to generate full or dominant hexahedral mesh starting from a provided arbitrary model i.e. a surface triangular mesh stored in STL ...
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2answers
106 views

Software to build a mesh of a surface from points on the surface

I have a set of points $(x_i,y_i,u(x_i,y_i))\in\mathbb{R}^3$, $i=1,\dots N$, over a surface $S$ (from experimental data). I need to calculate the integral of a function $F$ over that surface. If the ...
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0answers
25 views

Abaqus approach to simulate many flexible elements

I would premise that i am not an expert on the domain (i am a programmer that usally work with DB and data, not structural problem), but i have just see the work of a friend of mine and i am curious ...
4
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2answers
235 views

Meshing surface of a sphere with a subdomain

I am trying to build a triangle mesh of the surface of a sphere which also includes a subdomain defined by a 'polygon'. Here is a successful example (subdomain defined by the red dots): Note that the ...
2
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2answers
70 views

How to refine the tetrahedron if exist two longest length edge?

In some algorithms to refine tetrahedron, we need to calculate the longest edge. background If exist a tetrahedron with node ABCD, it has edges ...
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1answer
147 views

How to compute gradient of a cell having a boundary face?

In many situations in unstructured mesh solvers, one needs to compute gradient of arbitrary variable $\phi$ such as temperature or velocity at face centers (one of such situations is correction for ...
2
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1answer
99 views

Going From Blender Structure defined by triangles to full 3D mesh (Using GMSH?)

I currently have created a model airplane in Blender by drawing a closed volume with triangular planes. I want to do a FEM calculation on this object, meaning I need a fine 3D tetrahedral mesh of this ...
2
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1answer
541 views

How to calculate skewness for a mesh?

I am writing a code to calculate mesh quality stats such as: cell volume, face areas and non-orthogonality between faces (basically something like OpenFOAM's ...
2
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2answers
216 views

What are the best ways to interpolate a vector field inside (convex) polygons?

I want to interpolate a vector field inside convex polygons in a polygonal mesh. For triangular meshes the scheme uses a piecewise constant interpolation in the triangle, discretized at the center of ...
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0answers
64 views

FEM Meshing artifact at nodes with fewer neighbors

I wrote a 2D-FEM solver to solve some diffusion process and wanted to verify my code with a test problem. The input was $f(x,y) = x^2+y^2$ and I applied the stiffness matrix on it to get $\Delta f = 4$...
3
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1answer
146 views

FEM with elastic inhomogeneous properties leads to mesh-induced anisotropy

I'm solving an elastic homogenization problem and I'm having problems with mesh artifacts. I would like to first give a brief summary of what I do: I have a system with inhomogeneous (but isotropic) ...
2
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2answers
282 views

Visualization of Quad/Octree data Structures

I have a simple C++ quadtree implementation. The implementation subdivides node into four children as if there is more than one point in that particular node. At the moment I want to visualize how ...
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0answers
19 views

Volumetric Mesh Cutting Algorithms For Simulating Sculpture

I am interested in whether there an available algorithms to give me insights on how to cut a volumetric mesh?
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0answers
51 views

Finding isocontour lines, populating points on said lines (in MATLAB)

I'm trying to extract data from a potential field. I have an example code of a potential field, using meshgrid in MATLAB. I've pasted the code below. What I'd like to do next is 'convert' this field ...
2
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1answer
90 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 ...
0
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1answer
67 views

Parallel mesh partitioning

When a mesh partitioning takes place and every process works on a part of the mesh is any way to rename the global numbering of nodes(on each process) into a local numbering?Is there any software that ...
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0answers
143 views

Compute mass matrix in vibrations problem by using finite element method

I have to compute the mass matrix of a Hexahedral mesh. There are 3 methods to compute mass matrix. I'm interested in one method which consists of dividing the mass of the element by the number of ...
2
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2answers
1k views

How to determine the Jacobian Ratio for triangle element?

I am trying to implement an algorithm to find the Jacobian ratio for each triangle in mesh as a part of mesh quality check. Let's say that I have vertices of the triangle: $P_1(x_1, y_1, z_1)$, $P_2(...
5
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2answers
166 views

Effect of mesh size on solution curves for a 1D problem

I'm interested in studying the effect of mesh size on the behavior of the solution curves of 1D convection-diffusion problem. $$\frac{\partial C}{\partial t} = D\frac{\partial ^2 C}{\partial x^2} - ...
2
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1answer
172 views

mesh dependence of numerical adjoint solution

I am solving the steady, two-dimensional adjoint Euler equations, $$A_x^T \partial_x \Psi + A_y^T \partial_y \Psi = 0$$, where $A_x = \partial F_x/\partial U$ and $A_y= \partial F_y/\partial U$ are ...
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1answer
40 views

Produce vertex displacements from volumetric shrinkage data on unstructured meshes

I was wondering what would be an efficient way to produce compatible displacements for mesh nodes/vertices if the computed data is volume shrinkage of each element/cell in the unstructured mesh? ...
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0answers
100 views

FEniCS, refinement not 'respecting' domain boundary

Short question: how to ensure that extra points are not included as 'boundary' points after calling the refine function. More details. I am working with a hexahedral mesh in $3$d. Let $X$ be the set ...
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0answers
25 views

Direct and Inverse efficient mapping of 3D cartesian positions in a 1D array

I saved a sample of $N$ Cartesian locations $\{x_i, y_j, z_k\}$ inside a one-dimensional array $\mathbf{a} = \{a_l\}_{l = 1}^N$. How can I access back (efficiently) the $l$-location of the array $\...
1
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1answer
63 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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0answers
54 views

Determining the indices of a VTK mesh

I am trying to assign fixed constraint at specific indices of VTK mesh, however, I only can view STL file in a blender as follows: Upon assigning the favored indices in my scene at the SOFA physics ...
3
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2answers
135 views

Find shortest path around a cylinder represented by 3d triangular mesh

Suppose I have a 3d triangular mesh with the topology of a finite cylinder. Let $C$ be a vertex on that mesh. How can I find the shortest path from $C$ to itself that goes around the cylinder? By ...
3
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0answers
132 views

Is it possible to retain sets (physical tags) after remeshing the model in Gmsh?

I am currently working on a remeshing algorithm for Abaqus using Gmsh as part of my Bachelors thesis and I seem to be stuck at some point. I am able to remesh .geo and .msh files using the script ...
2
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1answer
184 views

Sorting Triangle vertices based on indices for alpha blending (back to front) C++, OpenGL

I have implemented in OpenGL alpha blending for a triangle mesh. I render this mesh using a vector of indices that indicate which vertex from a vertices vector should be drawn. The problem is to ...
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0answers
112 views

How to read data from simply formatted text file (c++)?

Mesh information like points, faces and cells is to be stored into separate files: e.g. for points file: # points data: x y z N_Points 100 x1 y1 z1 x2 y2 z2 ... cell file: # cells data: ...
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0answers
60 views

Stokes Equation fails to converge for an ellipse

This might be because of the mesh, but the following code blows up for all values of b not 1. Does anybody have any experience working with the ellipse mesh in Fenics? ...
4
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2answers
6k 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 ...
3
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1answer
76 views

Smoothness regularisation of a 2D field on a triangular mesh?

I'm working on an inverse problem where the solution is the values of a 2D scalar field at the vertices of a 2D triangular mesh, such that the field can be defined continuously inside the mesh via ...
0
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1answer
293 views

Node re-numbering in 1D mesh GMSH

I'm working with Gmsh to generate 1D meshes of polygon edges. I have noticed that drawing a polygon by "vertices and lines" the program always assigns to the first N nodes of the mesh the coordinates ...
1
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1answer
2k 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 ...
1
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1answer
187 views

Node renumbering in a 2D mesh

I have a 2D domain which is discretized using Q4 elements. I have the nodal positions and the element connectivity matrix. I would now like to renumber the nodes in such a way that all the interior ...
4
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0answers
785 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 ...
4
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2answers
571 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
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1answer
190 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 ...
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1answer
80 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
175 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
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1answer
445 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
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1answer
341 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
114 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
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1answer
154 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 ...
2
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1answer
586 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 ...