Gmsh mesh algorithm

Gmsh is an automatic 3D finite element mesh generator with build-in pre- and post-processing facilities. This is the Gmsh Reference Manual for Gmsh 4. Geuzaine and J. Remacle, Gmsh: a three-dimensional finite element mesh generator with built-in pre- and post-processing facilities. Gmsh is not in the public domain; it is copyrighted and there are restrictions on its distribution, but these restrictions are designed to permit everything that a good cooperating citizen would want to do.

What is not allowed is to try to prevent others from further sharing any version of Gmsh that they might get from you. Specifically, we want to make sure that you have the right to give away copies of Gmsh, that you receive source code or else can get it if you want it, that you can change Gmsh or use pieces of Gmsh in new free programs, and that you know you can do these things. To make sure that everyone has such rights, we have to forbid you to deprive anyone else of these rights.

For example, if you distribute copies of Gmsh, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must tell them their rights. Also, for our own protection, we must make certain that everyone finds out that there is no warranty for Gmsh. If Gmsh is modified by someone else and passed on, we want their recipients to know that what they have is not what we distributed, so that any problems introduced by others will not reflect on our reputation.

The precise conditions of the license for Gmsh are found in the General Public License that accompanies the source code see License. Detailed copyright information can be found in Copyright and credits.

If you want to integrate parts of Gmsh into a closed-source software, or want to sell a modified closed-source version of Gmsh, you will need to obtain a different license. Please contact us directly for more information. Next: How to read this manual? Gmsh is a three-dimensional finite element mesh generator with a build-in CAD engine and post-processor.

Its design goal is to provide a fast, light and user-friendly meshing tool with parametric input and advanced visualization capabilities. Gmsh is built around four modules: geometry, mesh, solver and post-processing.

Interactive actions generate language bits in the input files, and vice versa. A brief description of the four modules is given hereafter. A model in Gmsh is defined using its Boundary Representation BRep : a volume is bounded by a set of surfaces, a surface is bounded by a series of curves, and a curve is bounded by two end points.

Model entities are topological entities, i. This BRep is extended by the definition of embedded, or internal, model entities: internal points, edges and surfaces can be embedded in volumes; and internal points and curves can be embedded in surfaces. The geometry of model entities can be provided by different CAD kernels.

Gmsh does not translate the geometrical representation from one kernel to another, or from these kernels to some neutral representation. Instead, Gmsh directly queries the native data for each CAD kernel, which avoids data loss and is crucial for complex models where translations invariably introduce issues linked to slightly different representations. Both methodologies can also be combined. A finite element mesh of a model is a tessellation of its geometry by simple geometrical elements of various shapes in Gmsh: lines, triangles, quadrangles, tetrahedra, prisms, hexahedra and pyramidsarranged in such a way that if two of them intersect, they do so along a face, an edge or a node, and never otherwise.

Gmsh implements several algorithms to generate such meshes automatically. This implies that the mesh elements are completely defined simply by an ordered list of their nodes, and that no predefined ordering relation is assumed between any two elements. In order to guarantee the conformity of the mesh, mesh generation is performed in a bottom-up flow: curves are discretized first; the mesh of the curves is then used to mesh the surfaces; then the mesh of the surfaces is used to mesh the volumes.

In this process, the mesh of an entity is only constrained by the mesh of its boundary, unless entities of lower dimensions are explicitly embedded in entities of higher dimension. For example, in three dimensions, the triangles discretizing a surface will be forced to be faces of tetrahedra in the final 3D mesh only if the surface is part of the boundary of a volume, or if that surface has been explicitly embedded in the volume.

gmsh mesh algorithm

This automatically ensures the conformity of the mesh when, for example, two volumes share a common surface. For each meshing step, all structured mesh directives are executed first, and serve as additional constraints for the unstructured parts.

gmsh mesh algorithm

Contrary to most solver interfaces, the ONELAB server has no a priori knowledge about any specifics input file format, syntax, This is made possible by having any simulation preceded by an analysis phase, during which the clients are asked to upload their parameter set to the server.Released: Apr 9, View statistics for this project via Libraries. Tags mesh, gmsh, mesh generation, mathematics. Gmsh for Python. Gmsh is a powerful mesh generation tool with a scripting language that is notoriously hard to write.

The goal of pygmsh is to combine the power of Gmsh with the versatility of Python and to provide useful abstractions from the Gmsh scripting language so you can create complex geometries more easily. See here for the full documentation. To store the mesh, you can use meshio ; for example. The output file can be visualized with various tools, e. This software is published under the GPLv3 license. Apr 9, Mar 17, Feb 28, Feb 24, Feb 20, Feb 18, Aug 2, Jul 10, Apr 11, Apr 1, Mar 31, Mar 11, Mar 3, Sep 4, Jun 28, Jun 19, Jun 13, Jun 9, May 21, May 14, May 3, By using our site, you acknowledge that you have read and understand our Cookie PolicyPrivacy Policyand our Terms of Service.

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Study and Verification of Large-Scale Parallel Mesh Generation Algorithm for Centrifugal Pump

It only takes a minute to sign up. I have a simple question today. I am using GMSH 3. What I am looking to do is to set a different mesh size for different faces in my 2D geometry.

gmsh mesh algorithm

As a test, I am creating 2 squares next to each other. The square on the left will have a mesh size set by the element size factor in the options dialog. I typed my edge list and the face list that I want to restrict the field. However, I am still having difficulty in setting up a custom mesh size.

I am attempting to bound a face to specific mesh size. I am posting my. My question is this: What is the best method that I can do on the GUI in order to bound different faces to different mesh sizes? Please note that currently the Element size factor is set to 1. Also note that I am generating a mesh of only quads. So if you want an element mesh size of 0. If you specify different lc's for different points GMSH will interpolate between them.

Sign up to join this community. The best answers are voted up and rise to the top. Home Questions Tags Users Unanswered. Asked 2 years, 5 months ago. Active 2 years, 5 months ago. Viewed 3k times. In this section, it is stated that: A MathEval field specifies the size of the mesh using an explicit mathematical function. I also ensured that the 2D mesh algorithm is set to Delauney.

CFD Tutorial 10 - Geometry and Mesh Generation Tutorial in Gmsh

Active Oldest Votes. The Overflow Blog. Socializing with co-workers while social distancing. Featured on Meta.MeshKit is an open-source library of mesh generation functionality.

Its design philosophy is two-fold: it provides a collection of meshing algorithms for use in real meshing problems, along with other tools commonly needed to support mesh generation coordination of BREP-based meshing process, mesh smoothing, etc.

MeshKit has general mesh manipulation and generation functions such as Copy, Move, Rotate and Extrude mesh. In addition, new quad mesh and embedded boundary Cartesian mesh algorithm EBMesh are developed to be used. Interfaces to several public-domain tetrahedral meshing algorithms Gmsh, netgen are also offered. This library interacts with mesh data mostly through iMesh including accessing the mesh in parallel. It also can interact with iGeom interface to provide geometry functionality such as importing solid model based geometries.

For some non-existing functions in iMesh such as tree-construction and ray-tracing, MeshKit also interacts with MOAB functions directly. There are several algorithms and software tools built in MeshKit. A detailed list of all algorithms is available on the doxygen page: All MK Algorithms. A few software services offered by MeshKit are highlighted below:.

For general announcements, e. MOAB 5. Release notes are available here. SIGMA 1. The changelists and download instructions are available here. Please update your sources and let us know if you encounter problems. MeshKit Vitruvian Man.

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Search for:. Commits to MOAB. Commits to CGM. Commits to MeshKit. All Rights Reserved.In order to reveal the details of the internal flow in a centrifugal pump, a large-scale mesh is needed. However, the mesh generated by the serial grid algorithm cannot meet the calculation requirements due to the huge amount of time. A large-scale parallel mesh generation algorithm of a centrifugal pump for high-performance computers is presented in this paper. First, a grid point set for the 3D Delaunay triangular mesh on the surface of the centrifugal pump is generated.

Then, the S-H Sutherland—Hodgman algorithm for cropping and segmenting these grid point sets on the surface is employed. A uniform boundary mesh is generated and is divided into different subregions. In addition, in order to ensure the consistency of the interface mesh and to avoid the boundary mesh intersection overlap error, a parallel constrained Delaunay mesh generation algorithm based on region numbering is proposed, which can improve the quality and efficiency of the generated parallel mesh.

Finally, the centrifugal pump is tested for verifying the parallel mesh algorithm in the Tianhe-2 supercomputer. PIV particle image velocimetry internal flow experiment is comparatively analyzed with the numerical simulation of large-scale mesh.

The proposed algorithm not only ensures high grid quality with the serial grid algorithm but also accurately simulates the flow law in the centrifugal pump. The double-vortex structure which is obtained by PIV experiment is captured by the large-scale mesh. Centrifugal pump has strong rotation and large curvature, which usually requires a large-scale mesh of hundreds of millions of scales to reveal the complex turbulent flow.

However, there are serious performance bottlenecks in time and CPU storage to generate such a large-scale complex mesh on a single machine.

gmsh mesh algorithm

In addition, the design and manufacturing technology of high-performance computer hardware in China has been greatly developed, but there are still few software and applications dedicated to high-performance computers.

Therefore, in order to make better use of high-performance computers, developing the high-efficiency parallel mesh generation algorithm is an important way to solve the performance bottleneck in CPU storage and time when generating large-scale grid on a single machine [ 1 ] and enable high-performance computers to be used more effectively.

Parallel generation of mesh is a cross-cutting field of parallel computing and computational geometry. It is a complex technique of tightly coupled computational geometry, data structure, load balancing, and mesh partitioning. The CFD method is an effective and convenient method for numerical simulation, which provides intuition for further experiments. In terms of parallel logic, parallel mesh generation algorithm can be divided into two categories: algorithm parallel and problem parallel [ 3 ].

Algorithm parallelism is used to find out the degree of parallelism from the running process of serial algorithm, which can obtain multiple subtasks that can be executed concurrently. Algorithm parallel is generally fine-grained, and there are usually dependencies between each subtask, or data competition among each other.

So, the parallel algorithm produces a lot of communication and synchronization costs, which reduces the parallel efficiency of the algorithm.

The problem parallel algorithm is the application of parallel algorithm design through the divide-and-conquer strategy. Compared with algorithm parallel, it is usually a coarse-grained hierarchy. The generation process of a single clipped surface mesh is regarded as an inseparable parallel subtask in the problem parallel. The problem parallel algorithm includes data decomposition and data mapping, which decompose the problem into subproblems and assign subproblems to different processors [ 4 ], respectively.

The problem parallel algorithm only considers the perspective of data and does not need to be familiar with and master all aspects of the serialization algorithm [ 5 ]. The problem parallel algorithm can also reuse and inherit the serial algorithm very well compared with the algorithm parallel.

Gmsh 4.5.6

The problem parallel algorithm does not require more complicated expansion and design.In this example, we will tell GMSH to generate a boundary layer containing only one layer of prismatic elements. This is not always guaranteed to work, but is a good workaround for some cases. The geometry definition for this case is contained in the file SDRectangular. The contents of the GMSH configuration file are copied below.

The first thing the file does is set the far-field length to 10 and the surface length to 0. We've found that the BAMG algorithm does a good job at refining the mesh appropriately in areas of high curvature, as is the case at the wing tip near the trailing edge.

The default Delauney algorithm will be used for 3D meshing. It should be noted that these 'ghost' lines must have a physical ID of 0. For 3D meshes that completely contain a a geometry, as is the case in this example, the STEP file should consist of two closed or watertight surfaces, and each one will have an associated volume.

This means that the volume of the outer boundary will be a cube with the normal pointing outward. The volume for the wing will just include the volume contained in the wing, with the normal pointing out of the wing.

We will then need to define two surface loops, from which we will create our new volume using the SurfaceLoop command. Again, we generate a physical volume so GMSH will actually write out the volume elements.

The Box fields are not very important. There are so many because this case comes from an actual computational mesh for unsteady flow where it was necessary to refine around flow features. We choose AttractorAnisoCurve in order to refine around the leading edge, composed of two lines with geometric IDs 14 and Note that since we are not using an anisotropic algorithm for 3D meshing, the mesh will not be anisotropic near the leading edge.

However, we find that AttractorAnisoCurve is more general, and allows for anisotropic meshes to be generated by simply changing the 3D meshing algorithm. Why don't we use a 3D anisotropic algorithm for this case, you ask? Now, let's take a look at the BoundaryLayer field.

We want to generate a boundary layer with just a single layer, which MeshOpt will make high order and finally subdivide. We've found this process to be much easier than subdividing the boundary layer first and then trying to untangle the elements.

We indicate that we would like to generate a BL on all the wing surfaces with a thickness of 0. In reality, we actually want the boundary layer thickness to be 0. We then set the background field as before.

The contents of MeshOpt. The primary difference between this configuration file and that of the previous examples is that we use the boundary layer generated by GMSH instead of our own. We can now generate the high order mesh with MeshOpt. Again, we see that the surface is not plotted smoothly, since GMSH assumes we generated the mesh with equispaced points.

If we make another mesh, this time with equispaced node locations, we will see a nice smooth surface:. Skip to content.Gmsh is an open source 3D finite element mesh generator with a built-in CAD engine and post-processor. Its design goal is to provide a fast, light and user-friendly meshing tool with parametric input and advanced visualization capabilities.

Gmsh is built around four modules: geometry, mesh, solver and post-processing. The specification of any input to these modules is done either interactively using the graphical user interface, in ASCII text files using Gmsh's own scripting language. The source code repository contains many examples written using both the built-in script language and the API see e. Make sure to read the tutorials before sending questions or bug reports. If you use Gmsh please cite the following reference in your work books, articles, reports, etc.

Geuzaine and J. Gmsh: a three-dimensional finite element mesh generator with built-in pre- and post-processing facilities. International Journal for Numerical Methods in Engineering 79 11pp.

You can also cite additional references for specific features and algorithms. To help fund Gmsh development, you can make a donation. Gmsh is copyright C by C. In short, this means that everyone is free to use Gmsh and to redistribute it on a free basis. Gmsh is not in the public domain; it is copyrighted and there are restrictions on its distribution see the license and the related frequently asked questions. For example, you cannot integrate this version of Gmsh in full or in parts in any closed-source software you plan to distribute commercially or not.

If you want to integrate parts of Gmsh into a closed-source software, or want to sell a modified closed-source version of Gmsh, you will need to obtain a different license. Please contact us directly for more information.

These are two screenshots of the Gmsh user interface, with either the light or dark user interface theme. Current stable release version 4. Gmsh C. Remacle, C. Geuzaine, G. High-quality surface remeshing using harmonic maps. International Journal for Numerical Methods in Engineering 83 4pp. Marchandise, C. Carton de Wiart, W. Vos, C. High quality surface remeshing using harmonic maps. Part II: surfaces with high genus and of large aspect ratio. International Journal for Numerical Methods in Engineering 86 11pp.

Marchandise, J.


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