Tuesday 3 April 2018 photo 8/49
|
Gambit mesh generator
-----------------------------------------------------------------------------------------------------------------------
=========> gambit mesh generator [>>>>>> Download Link <<<<<<] (http://hovuxik.bytro.ru/21?keyword=gambit-mesh-generator&charset=utf-8)
-----------------------------------------------------------------------------------------------------------------------
=========> gambit mesh generator [>>>>>> Download Here <<<<<<] (http://jdedhw.dlods.ru/21?keyword=gambit-mesh-generator&charset=utf-8)
-----------------------------------------------------------------------------------------------------------------------
Copy the link and open in a new browser window
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
..........................................................................................................
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
dear all, Im a new in CFD. I want to mesh a hemisphere in Gambit. what is the best meshing for hemisphere in gambit. please help me if someone know. Fluent Inc.a single interface for geometry creation and meshing that brings together all of Fluent's preprocessing technologies in one environment. Advanced tools for journaling let you edit and conveniently replay model-building sessions for parametric studies. GAMBIT provides a concise and powerful set of solid. ME469B/2/GI. 2. Geometry Modeling & Grid Generation. • Geometry definition (simple shapes, CAD import). • Grid generation algorithms. • GAMBIT. • Grid quality and improvement. • Automation. Acknowledgements: Fluent Inc. Gambit User Manual. S. Owen: Introduction to unstructured mesh generation. This tutorial illustrates geometry creation and mesh generation for a simple geometry using GAMBIT. In this tutorial you will learn how to: • Start GAMBIT. • Use the Operation toolpad. • Create a brick and an elliptical cylinder. • Unite two volumes. • Manipulate the display of your model. • Mesh a volume. • Examine the quality. Gambit -3d geometry and mesh generation - Download as PDF File (.pdf), Text File (.txt) or read online. Gambit - Generation of Grid for a 2-D Airfoil. Introduction and Instructions: In this document is a procedure that enables students to generate a two-dimensional, unstructured grid around an airfoil, which will be used with the CFD program, Fluent. Readers should already be familiar with the notation used in this module,. GAMBIT Logo. GAMBIT is an end-to-end application developped at UNC-Chapel Hill allowing Group-wise Automatic Mesh-Based analysis of cortIcal Thickness as well as other surface area measurements. This cross-platform tool can be run within 3D Slicer as an external module, or directly as a command line. Download. I would say ANSA (BETA CAE System) for mesh generation. It has got many features to generate mesh. Meshing The integrated Batch Meshing tool leads to controllable and effortless optimal results, for both shell and volume meshing. Following the ver... Take a "FREE" course on ANSYS GAMBIT. Learn concepts like geometry creation, clean up and domain decomposition using ANSYS GAMBIT. Get expert answers to your questions in Gambit, Mesh, FLUENT Gambit and Mesh Processing and more on ResearchGate, the professional network for scientists.. I tried the second strategy, the first generation of mesh (only Tetra) produce about 5 mil. meshes. After converting those to Polyhedral, it reduced into 1.5 mil. of. GAMBIT is geometry and mesh generation software for computational fluid dynamics (CFD) analysis. GAMBIT has a single interface for geometry creation and mesh... Download Gambit for free. A library of tools for doing computation in game theory. Running Gambit. Before performing a calculation using Fluent, a computational domain must be generated to define the geometry of problem as well as grid resolution. Log on and. for which gambit will eventually write the mesh file. Create some.. generation, and will have to go back and regenerate the grid. 3. Look at. supplies meshing. parameters. Analysis Code. supplies meshing. parameters. Computational Modeling Sciences Department. 5. Geometry. Mesh Generation... 144. Unstructured-Hex. http://www.numeca.be/hexpress_home.html. Grid-Based. Gambit, Fluent, Inc. Computational Modeling Sciences Department. 145. gambitToFoam: reads a GAMBIT.neu neutral file;; ansysToFoam: reads an I-DEAS mesh written in ANSYS.ans format;; cfx4ToFoam: reads a CFX mesh written in .geo. When mesh generation in is completed, remove any extraneous vertices and compress the cells boundary and vertex numbering, assuming that fluid cells. Step 1: Create Geometry in GAMBIT. If you would prefer to skip the mesh generation steps, you can download the mesh from here and go straight to step 4. In an external flow such as the flow past a cylinder, we have to define farfield boundaries and mesh the region between the cylinder geometry and the. A mesh file converter : cmesh. cmesh --from gambit|gmsh|netgen|tetgen|matlab|triangle> --to -i [-o ] [-n ] [--version] [-h]. where:. Gmsh is a free three-dimensional finite element mesh generator with built-in pre- and post-processing facilities. It can be. 2. Check quality of boundary mesh. 3. Improve and repair boundary mesh. 4. Generate volume mesh. 5. Perform further refinement if required. 6. Inspect quality of volume mesh. 7. Remove sliver and degenerate cells. 8. Save volume mesh. Surface mesh for a grid containing only tetrahedra. Mesh generation process. PARALLEL MESH GENERATION. The GAMBIT serial mesh generation tools have historically been used to generate unstructured meshes for SeisSol simu- lations. Given a complex geometric model though, such as. Landers, additional geometric model faces are required to sub- divide the domain and aid GAMBIT mesh. The first parameter defines the input file format: 1) .grd : Elmergrid file format 2) .mesh.* : Elmer input format 3) .ep : Elmer output format 4) .ansys : Ansys input format 5) .inp : Abaqus input format by Ideas 6) .fil : Abaqus output format 7) .FDNEUT : Gambit (Fidap) neutral file 8) .unv : Universal mesh file format. The next step involves the preparation of vertex data and journal files for Gambit and Fluent, and their transfer to the Globus server. The vertex data file for a NACA four digit airfoil is a text file containing the coordinates of the airfoil, which are used by the mesh generation tool Gambit. The journal files for Gambit and Fluent. Import the current glass geometry into a mesh generator and generate a completely new, undistorted mesh. 3. Interpolate the field variables from the old grid to the new grid and restart the calculation. POLYFLOW, together with its pre-processor GAMBIT [4.56], provides all the ingredients (i.e., automatic mesh generation,. Mesh generation is the practice of generating a polygonal or polyhedral mesh that approximates a geometric domain. The term "grid generation" is often used interchangeably. Typical uses are for rendering to a computer screen or for physical simulation such as finite element analysis or computational fluid dynamics. keywords: hexahedra; mesh generation; medial axis; Voronoi diagram; embedded Voronoi graph; decomposi- tion. 1 Introduction. Computer simulation of physical.... suitability for meshing by mapped mesh, submap, sweeping and extended sweeping (like [17]) can be similar to those used in Fluent's Gambit [25] software. re-meshes if required & remaps physical parameters to initiate another case,. moving mesh for free surface flows or solid walls,. supports command line interface and script file for parametric mesh generation,. import mesh in CGNS, IDEAS, GAMBIT, NASTRAN, ANSYS formats,. create Hexahedral, tetrahedral, triangular. Gambit2semtex, a FORTAN-based converter from Fluent Inc's gambit mesh generator format to semtex session file format. Written by Erik Torres and Jörg Stiller from the ILR group at TU-Dresden, has user guides in German and English. With the deletion of gambit from the Ansys code suite, note that the Ansys workbench. ANSYS ICEM CFD is a popular proprietary software package used for CAD and mesh generation. Some open source software includes. in arriving at the meshing stage quickly. Unlike the concept of volume in tools like GAMBIT, ICEM CFD rather treats a collection of surfaces which encompass a closed region as BODY. Next, the vertex file describing the airfoil under consideration is transferred to the remote Globus server, where it will be used by the mesh generation tool Gambit. Meshing and solution is controlled by a pair of user-prepared journal files that define the work to be carried out by Gambit and Fluent. These files are tailored. Numerical method: Which numerical method(s) to employ for defining a suitable solution procedure for the problem. ▻ Mesh generation: How to represent the domain of interest for use in our solution. procedure and mesh generation as two distinct problems... gambit(Fluent, Inc) *.neu format is assumed.
What is GAMBIT? A single, integrated preprocessor for CFD analysis: Geometry construction and import. Using ACIS solid modeling capabilities; Using STEP, Parasolid, IGES, etc. import. Cleanup and modification of imported data. Mesh generation for all Fluent solvers (including FIDAP and POLYFLOW). Structured and. 41.2 with the boundary conditions used in the CFD simulation. The numerical analysis is carried out using finite volume scheme via commercial software FLUENTÒ 6 and the mesh is generated using GAMBIT mesh generator software. A uniform fine quad map mesh is used with refined mesh near the wall. A grid refinement. A three-dimensional finite element mesh generator with built-in pre- and post-processing facilities. Christophe Geuzaine and Jean-François Remacle. Download | Documentation | Licensing | Screenshots | Links | References | facebook | twitter. Gmsh is a free 3D finite element mesh generator with a built-in CAD engine and. Geometry. Modifications. Meshing. Solver. Meshing Methods. Hybrid Mesh: Tet,. Prisms, Pyramids. Hexa Dominant,. Sweep meshing. Global Mesh. Settings. Local Mesh. ICEM CFD, TGRID (Fluent Meshing), CFX-Mesh, Gambit. •. Able to adapt and create Meshes.. Generation of wedges. & hex elements. unnecessarily constrain the mesh generation process. Using the “merge faces" command,. GAMBIT allows you to easily combine these surfaces prior to meshing. You can then have GAMBIT automatically create a triangular mesh on the car body. Since the imported geometry consists only of the car body, you need to create. Gambit - Generation of Grid for a 2-D Airfoil. Overall description of the problem and grid: We will model flow over a 2-D airfoil at some arbitrary angle of attack with respect to the freestream flow. The computational domain is bounded on the inside by an airfoil shaped closed path, and by a rectangular box on the outside,. Mesh Generation. GAMBIT offers state-of-the-art mesh generation technology in a powerful, yet easy-to-use interface. Extensive automation dramatically reduces meshing time for many applications. Edge Meshing for Precise Control. • Defined interactively with real-time, graphical feedback. • Multiple grading schemes. Computational analysis is done with Fluent 6.3.26 with Gambit 2.4.6 mesh generation using Cooper meshing facility. Eulerian–Lagrangian approach is adopted in the simulation with air as a working fluid and assumed to have continuous properties (Continuum). The collection efficiency of single and double inlet separator. Generating meshes for computational fluid dynamics is neither easy nor fun. But mesh generation is where you have the most direct influence on how fast, how converged and how accurate your CFD solutions is. 2. Check quality of boundary mesh. 3. Improve and repair boundary mesh. 4. Generate volume mesh. 5. Perform further refinement if required. 6. Inspect quality of volume mesh. 7. Remove sliver and degenerate cells. 8. Save volume mesh. Surface mesh for a grid containing only tetrahedra. Mesh generation process. The grid will be scaled back to original dimensions in. FLUENT. 2. Correct order of grid generation a. Put nodes on all the EDGES b. Mesh the FACE c. Mesh VOLUME. 3. If any of the above steps are omitted i.e. you go directly to meshing FACE without meshing the EDGE,. GAMBIT puts a mesh of default size on the lower. Complex Geometries & Meshes. ○ Various and mixed meshes. – Structured, unstructured, & mixed. ○ Sliding meshes. ○ Mixing-plane model. – Time averaged mesh boundaries. ○ Dynamic (deforming) meshes. ○ Free surfaces. ○ GAMBIT: mesh generation. ○ T-GRID: merge meshes. The mesh information is stored to be used for multiple simulations: for these mesh files we used the ASCII-based GAMBIT format, so far.. retain the flexibility regarding mesh generator and partitioning software for individual users, we decided not to integrate the mesh generator into SeisSol, as for example proposed in [3]. Fluent's new pre-processor, GAMBIT 1.0, provides users with the latest technology for geometry modelling and mesh generation. A broad spectrum of companies worldwide use CFD-based virtual prototyping in order to reduce design times and improve performance. The software enables the engineer to build a computer. Generating a good mesh is a large part of the CFD problem. Solid regions like tank baffles can be generated by blanking those mesh points. – A free PowerPoint PPT presentation (displayed as a Flash slide show) on PowerShow.com - id: 137c07-ODQzN. TG New Methods: Algorithms, Grid Generation, Code Library. 18th - 20th July 2005. Munich, Germany. Two- and three-dimensional unstructured, high quality mesh generation using ICEM and GAMBIT. Martin Käser, Josep de la Puente. DICA, University of Trento. Dep. of Earth and Environmental Sciences, LMU Munich. The boundary layer mesh generator described in the previous chapter has been tested against a wide range of complex models for generation of multi-million meshes for fluid flow simulations. The mesh generator has been used for various applications such as capturing thermal boundary layers for complex automobile. Import the airfoil coordinates by going to File/Import/Vertex Data/ and pickup the file naca0016.dat file from the computer. The file should be a simple ascii file having 3 columns of x, y, z coordinates. Step 2. Creating the geometric domain: 1. Gambit is a single precision grid generator, so when we are having a boundary. Results 1 - 20 of 492. More on the projects using. envelopes, Minkowski sums), mesh generation (2D Delaunay mesh generation and 3D surface and volume mesh. generation, skin surfaces), geometry processing.. Referenced in 20 articles [sw06529]; GAMBIT is Fluent's geometry and mesh generation software. Gambit and Fluent, and their transfer to the Globus server. The vertex data. file for a NACA four digit airfoil is a text file containing the coordinates of the airfoil, which are used by the mesh generation tool Gambit. The journal. files for Gambit and Fluent are tailored according to various input parame- ters entered by the user.
For example, in the engineering design domain a mesh generation service has a geometry file as its input, which is linked to a geometry generation service, and a mesh file as its output, which leads to the code analysis service. The mesh generation service itself uses the Gambit meshing tool as its process model. FIDAP Structure. FI-GEN: Mesh generation module (This is now replaced by gambit); FICONV: Convert Gambit Mesh data to FIDAP mesh; FIPREP: Problem data specification. type of problems and equations, solution procedure,; fluid / material properties,; initial and boundary conditions. FISOLV: Computational simulations 2.1 Conversion; 2.2 Generation; 2.3 Manipulation; 2.4 Other tools. 3 Surface mesh; 4 Miscellaneous; 5 Parallel processing; 6 Post-processing. 6.1 Data converters; 6.2 Graphics; 6.3 Lagrangian simulation; 6.4 Patch data; 6.5 Scalar fields; 6.6 Sampling; 6.7 Stress fields; 6.8 Turbulence; 6.9 Velocity field. Image-based mesh generation in the field of cardiology. Bernhard Quatember. University. by a section focusing on a semi-automatic mesh generation method which allows us to generate a high-quality mesh. commercial mesh generator. GAMBIT and a new meshing approach to attain a high-quality mesh (for details we. Fluent: a product of Fluent, Inc.; one of the standards, world wide, in CFD codes; part of a large suite of CFD software, including compressible flow simulation capability and the extremely capable, but somewhat difficult-to-master, grid generator GAMBIT. http://www.fluent.com. 4. STAR-CD: also a world-wide CFD standard. Who we are. Computational Simulation Software, LLC (csimsoft) is a privately held software developer of high-quality engineering simulation software. We specialize in geometry preparation and mesh generation software for the Finite Element Analysis and Computational Fluid Dynamics communities worldwide. If a coarse grid is used to simulate, the accurate results cannot be obtained. However, using a finer grid need to spend much more time. In this paper, near-wall boundary layer mesh and various grid spacing of working face and gob are constructed with Gambit and respectively with Fluent simulation near-wall boundary. This guide contains step-by-step examples that teach you how to use GAMBIT to create and mesh various geometries. Each example illustrates at least one new concept with respect to GAMBIT geometry creation and mesh generation. Tutorial 1 includes explicit instructions for all steps in the geometry creation, mesh gen-. Find Gambit Mesh Generators related suppliers, manufacturers, products and specifications on GlobalSpec - a trusted source of Gambit Mesh Generators information.. RF generators and high frequency power supplies provide the power required for plasma generation, induction heating, and radar or communications. Also built into these interfaces are automatic mesh generation routines to create the required computational meshes. The geometry/mesh preprocessor for FLUENT is called GAMBIT*. In the second example shown below GAMBIT was used to generate 3D geometry and create an unstructured grid. Application To Air Quality. Grid generation is often quoted as the most important and most time consuming part of CFD analysis. The quality of the grid plays a direct role on the quality of the analysis, regardless of the flow solver used. Additionally, the solver will be more robust and efficient when using a well constructed mesh. 7. UGM 2002. Confidential. Why G/Turbo? ◇ Automated tool for turbomachinery blade rows. ◇ Important application for Fluent customers. ◇ Greatly reduces setup time for geometry and mesh generation. ◇ Expect more tools like this in future. More generally - http://www.flow3d.com/Cfd-101/cfd101.htm. GAMBIT: Geometry and Mesh Generation GAMBIT is Fluent's geometry and mesh generation software. GAMBIT's single interface for geometry creation and meshing brings together most of Fluent's preprocessing technologies in one environment. GAMBIT: A geometric modeling and grid generation tool often shipped with FLUENT technology. GAMBIT software allows users to create their own geometry or import geometry from most CAD packages. It can automatically mesh surfaces and volumes while allowing the user to control the mesh through the use of sizing. High quality mesh is one of the main criteria for the successful CFD analysis. Our experienced team are able to do variety of meshing job in specified time. Using ANSYS ICEM CFD & GAMBIT, mech-well offers a complete grid generation to our clients who are mostly interested in end product analysis rather than to involve in. GAMBIT offers state-of-the-art mesh generation technology in a powerful, yet easy-to-use interface. Extensive automation dramatically reduces meshing time for many applications. Edge Meshing for Precise Control. ♢ Defined interactively with real-time, graphical feedback. ♢ Multiple grading schemes include geometric ratio. and adaptive mesh refinement strategies. Mark Merrifield is a.. Grid generation. Unstructured grid generation has proven to be a complex task because a triangulation in which the. GAMBIT (Fluent, Inc, 2001) unstructured grid generating package, which will hopefully resolve these issues. Figure 2. The New Release of This State-of-the-Art Computational Fluid Dynamics (CFD) Software for Modeling and Meshing Tightens the Link Between CAD and Flow... mesh geometry in GAMBIT, specify boundary types in GAMBIT, set up problem in FLUENT, solve the problem and analyze the results.. Keywords: Fluid Flow, Aerodynamics, Airfoil and Vortex Generator.. without spoiler and with spoiler at different angle is drawn in GAMBIT 2D simulation. The problem. 4. DESIGN PROCESS. 19. 4. 1. Introduction. 19. 4.2. Gambit. 20. 4.2.1. Geometry. 20. 4.2.2. Mesh. 23. 4.2.3. Boundary conditions. 25. 4.3. Analysis in Fluent. 27.. In these turbines the generator is located at the bottom of the tower and so it can be.. from here to the electrical generator, that provide the electricity to the grid. THE MESH. The mesh has been generated with Gambit 2.04. Geometry generation. In order to control all the parameters of the mesh, it is necessary to use a tip in order to create the geometry. Indeed, for our case it is impossible to create a mesh with regular cells with Gambit. Hereafter is the algorithm in order to create the. “Components", Hypermesh stores them in “Collectors" and GAMBIT stores them in “Zones". The sizing control in all preprocessors have the following precedence: Global Size Point: Equivalent to "Mesh Density" option in ICEM & Keypoint Sizing in Ansys. CREATING AND MESHING BASIC GEOMETRY. This tutorial illustrates geometry creation and mesh generation for a simple geometry using GAMBIT. In this tutorial you will learn how to: • Start GAMBIT. • Use the Operation toolpad. • Create a brick and an elliptical cylinder. • Unite two volumes. • Manipulate the display of. 1.2 Program Structure. Your FLUENT package includes the following products: FLUENT, the solver. prePDF, the preprocessor for modeling non-premixed combustion in FLUENT. GAMBIT, the preprocessor for geometry modeling and mesh generation. TGrid, an additional preprocessor that can generate volume meshes. Hope this helps, > > > > - Josh > > -----Original Message----- > > From: nek5000-users at lists.mcs.anl.gov > > Date: Fri, 21 May 2010 18:39:51 > > To: users at lists.mcs.anl.gov> > > Subject: [Nek5000-users] NEKTON and Gambit > > > > Hello all, > > > > I notice that Fluent's grid generator Gambit. Overview. Funding from this grant has been used to buy a license for GAMBIT, the mesh generator software needed by. SUNTANS, an advanced hydrodynamic model developed by Stanford University that is being implemented by. ICIT for the Pentland Firth. Benefits of this award. The mesh or grid of a numerical simulation. TABLE OF CONTENTS. 1 Introduction 1.1 Background 1.2 Literature Review 1.2.1 History 1.2.2 Present Research and Development 1.3 Objectives 1.4 Research Methodology. 2 Mesh Generation in GAMBIT 2.1 Mesh Design - 2D 2.1.1 Known Parameters 2.1.2 Inlet Velocity Calculation 2.1.3 Boundary Layer Calculation In this tutorial, we provide guidelines for Cutcell Mesh Generation for a manifold in ANSYS Fluent.This technique can be used for a variety of applications. A brief survey of some of the fundamental algorithms in unstructured mesh generation is presented. Included is. mesh generation, I have limited this survey to include what I consider the more fundamental aspects of the field. Since I.... 45 Fluent, Gambit web site: http://www.fluent.com/software/gambit/gambit.htm. 46 S.H.. http://www.nitrc.org/projects/gambit/. An end-to-end application allowing Group-wise Automatic Mesh-Based analysis of cortIcal Thickness as well as other surface area measurements.. analyze, c++, linux, mesh generation, modeling, magnetic resonance, nrrd, posix/unix-like, surface analysis, thickness, workflow. The author of this book, is basically considered "the father of grid generation", because he came up with the Elliptic mesh for mesh generation. Unstructured meshes. Also, there have been some codes which can convert a cartesian mesh to a unstructured Delaunay mesh and vice-versa (e.g. Gambit). I don't think these. Mesh Generation. ➢ blockMesh. – For simple geometries, there is blockMesh, a multi-block mesh generator that generates meshes of hexahedra from a text configuration file. – Look at the OpenFOAM distribution. Converts a GAMBIT mesh to OPENFOAM® format. gmshToFoam. Reads .msh file as written. Gambit - Generation of Grid for a Cylinder or Sphere Introduction and Instructions : In this document is a procedure that enables students to generate a two-dimensional, structured grid around a half circle, which will be used with the CFD program, Fluent to solve for flow around a circular cylinder (two-dimensional) or around. Choose a project name, e.g. cyl and start Gambit with gambit -id cyl. The Gambit mesh generator will start. Create nodes, faces, node density, generate mesh and name faces. Save the finished mesh with the menu File>Export>General file>*.neu. Exit gambit, rename the mesh file to meshfile.neu and logout. learning gambit/fluent cfd - physics forums - Learning Gambit/Fluent CFD Page 1 of 2 1 2 Next > and if there is a manual that explain different lines of Gambit output file that shows the points coordination. 2d mesh generation (gambit) - page 2 - Computational Fluid Dynamics (CFD) - 2D Mesh Generation. Mesh generation. Unstructured mesh is used in the present study to discretize the computational domain into a finite number of control volumes by using the finite–volume scheme. The model was meshed by GAMBIT software [7]. The refinement and generation of mesh system are very crucial to predict the heat transfer in. High order grid generation. Application. Conclusion. Generating the curved mesh commercial mesher: ANSA, ICEM, (Gambit) linear hybrid mesh curved boundary faces surface normal(s) on corner nodes extract exact normals from CAD. ICEM build-in. “spectral elements". ANSA build-in. “subdivision". Chebychev-Lobatto. Assemble the system of algebraic equations and solve the system to get approximate solutions Numerical Methods: ul>Discretization methods Solvers and numerical parameters Grid generation and. An overview of Gambit. Download gambit mesh. Instant download and detailed guides on installation for all nude skins. Learn more about ANSYS AIM Student and. Gambit, you can build, analyze, and explore game models. Latest Version and Single Link for. Geometry Modeling Grid Generation. DEAS and CFX mesh. GAMBIT, Iceboard, Icechip, Icemax, Icepak, Icepro, Icewave, MixSim, POLYFLOW, TGrid, and any and all ANSYS, Inc. brand,.. Reading GAMBIT and GeoMesh Mesh Files . . . . . . . . . . . . 4-9. 4.2.4. Reading.... 12.13.2 Including Turbulence Generation Due to Buoyancy . . . . . . . . 12-27. 12.13.3 Vorticity- and.
Annons