Questions tagged [mesh]

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21 views

Help in agglomerating a mesh with Metis?

I have got a mesh of triangles (for a finite element code) that I'd like to partition into polygons, much better if convex. I tried metis and it is very complicated but powerful if one knows about ...
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1answer
104 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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31 views

Gmsh undesired behaviour 3D mesh

I would like to generate a 3D hexahedral mesh starting from a STL file using Gmsh 4.8.0. I followed these steps: Opened a STL file: file->open Added a volume: Modules -> Geometry -> ...
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48 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
96 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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22 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 ...
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2answers
130 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 ...
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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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0answers
39 views

Show deformed mesh in Comsol

I am using COMSOL Multiphysics 5.2a in order to do thermal, mechanical and thermo-mechanical simulations. Due to a boundary load, my components get deformed which I can simulate very well. However, ...
2
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1answer
106 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
64 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
186 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 ...
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2answers
144 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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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 $\Delta f = 4$...
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1answer
131 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) ...
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2answers
137 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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18 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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99 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 ...
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0answers
27 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
73 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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23 views

RANS equations in the ALE formulation

I am simulating an incompressible flow of a newtonian fluid over an oscillating plate using OpenFOAM . As far As I know, in this case, OpenFOAM uses the Arbitrary Lagrangian Eulerian formulation. ...
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81 views

Import stl file into Gmsh and create a 3d mesh for CFD

I am trying to develop a case study for teaching CFD. To this end, I am using OpenVSP, Gmsh and SU2. I have created a wing in OpenVSP, exported the CFD mesh as .stl file. Opened the .stl file in Gmsh ...
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1answer
63 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
85 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 ...
3
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2answers
516 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(...
4
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2answers
138 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
165 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
39 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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85 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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23 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 $\...
2
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1answer
54 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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51 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 ...
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2answers
118 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 ...
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0answers
106 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
91 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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90 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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54 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
4k 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
72 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 ...
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1answer
205 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 ...
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1answer
1k 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
154 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 ...
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0answers
594 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
546 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
182 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 ...
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1answer
127 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
395 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
276 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
108 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....