Ansys user manual free download

As an engineer, you may need to test how a design interacts with fluids. For example, you may need to simulate how air flows over an aircraft wing, how water flows through a filter, or how water seeps under a dam. Carrying out simulations is often a critical step in verifying that a design will be successful.

The goal is to reduce the number of elements that are attached to one vertex by refinement in problem regions. Laplace smoothing This option will solve the Laplace equation, which will generally yield a more uniformly spaced mesh. Note This can sometimes lead to a lower determinant quality of the prisms.

Also, this option works only for the triangular surface mesh. This is enabled by default, and is often very useful in improving the grid quality. Typically, when a mesh is smoothed, the smoother concentrates on improving the worst regions; this option will allow the smoother to continue smoothing beyond the worst regions until the desired quality is obtained.

Surface fitting This option will smooth mesh, keeping the nodes and the new mesh restricted along the surface of the geometry.

Only Hexa models will utilize this option. Ignore PrePoints This option will allow the smoother to attempt to improve the mesh quality without being bound by the initial points of the geometry. This option is similar to the Violate geometry option, but works only for points located on the geometry. This option is available only when there are hexahedral elements in the model. Usually, the best way to improve the quality of grids that cannot be smoothed above a certain level is to concentrate on the surface mesh near the bad elements and edit this surface mesh to improve the quality.

Prism Mesh Tetra meshing is not efficient for capturing shear or boundary layer physics. Prism mesh efficiently captures these effects near the surface while maintaining the ease and automation of Tetra mesh. Prism has always been necessary for CFD customers, but now that the option is more widely available, many other branches of CAE have started using prisms to better resolve the physics perpendicular to the surfaces of their models.

The rate of volume change between cells is also important. Calculations are done between nodes or elements, and Prism mesh gives you more elements perpendicular to the surface. This efficiently allows for better resolution more calculations per unit distance of the solution normal to the surface, without increasing the number of elements along the surface. This gives you a quicker and more accurate solution than a very fine tetra mesh. The height and direction of the prism layer extrusion are calculated on an element by element basis and may vary due to global or local controls, or for improved quality.

You may want to set the initial height, number of layers and growth ratio, and then they limit this with the Prism height limit factor. Or you may prefer to just set the number of layers and growth ratio. This allows Prism to adjust the initial height and locally optimize the volume transition between the prisms and tetras. Prism parameters are set globally, but can then be adjusted on a part by part or entity by entity basis.

Entity settings override global settings and between entities, the smaller size overrides the larger. For instance, 3 layers could be set for a growth rate of 1. On a specific entity within that part or another part, you could set a specific parameter. If you set prism parameters, such as height, on a curve entities, it will interpolate that parameter across the surface between the curves.

You may notice that you can also select volume parts for prism. If no volume parts are selected, it will assume that you want to grow prisms into all volumes bordering the prism surfaces.

If you select spe- cific volume parts, then prism will only be grown into those volumes. After each layer is extruded, smoothing is done according to the global settings. The layers are grown one at a time. This continues until all the requested layers are grown. You can add prisms to exiting layers or you can subdivide and redistribute layers at a later date.

You can save time by growing only a few thicker layers and then subdividing them into many layers. The smoothing is the most time con- suming part, so for simple configurations, it may be best to turn off all smoothing but grow all the layers one at a time. This allows you to take advantage of the variable height feature. This option can create prisms from existing volume or surface mesh. Prism Mesh Process The prism mesh process generates prism elements near boundary surfaces from tetrahedral or tri surface mesh.

This batch process creates prisms by extrusion of the surface mesh, and the resulting prisms are made conformal with any existing tetrahedral volume mesh. The prism mesh can be smoothed to yield the necessary quality. Prism Mesh Preparation When generating prism mesh, preparation is key. It is easier to edit a tetra mesh than a tetra prism mesh. Prism mesh can also be difficult to smooth, so it will save time to start with good quality tetra or tri surface mesh.

Start with the best possible initial hybrid mesh quality Hybrid mesh is generally difficult to smooth. Look for any surface discrepancies or sharp tent-like structures in the mesh.

Look for a few elements of one part scattered among another part. Extruding from a few isolated elements will likely crash the prism mesher.

Modify part assignments of such ele- ments. Decrease the Up to quality value, so that the prism elements are not distorted too much. Hexa Hexa is a 3D object-based, semi-automatic, multi-block structured and unstructured, surface and volume mesher.

The block topology model is generated directly on the underlying CAD geometry. Within an easy-to-use interface, those operations most often performed by experts are readily accessible through automated features.

There is access to two types of entities during the mesh generation process in Hexa: block topology and geometry. After interactively creating a 3-D block topology model equivalent to the geometry, the block topology may be further refined through the splitting of edges, faces and blocks. In addition, there are tools for moving the block vertices -- individually or in groups -- onto associated curves or CAD surfaces.

You may also associate specific block edges with important CAD curves to capture im- portant geometric features in the mesh.

Moreover, for models where you can take advantage of symmetry conditions, topology transformations such as translate, rotate, mirror and scaling are available. The simplified block topology concept allows rapid generation and manipulation of the block structure and, ultimately, rapid generation of the hexahedral meshes. Hexa provides a projection-based mesh generation environment where, by default, all block faces between different materials are projected to the closest CAD surfaces.

Block faces within the same material may also be associated to specific CAD surfaces to allow for definition of internal walls. In general, there is no need to perform any individual face associations to underlying CAD geometry, which further reduces the difficulty of mesh generation. Edge-Meshing Parameters: Hexa's edge-meshing parameters offer unlimited flexibility in applying user specified bunching requirements.

Time Saving Methods: Hexa provides time saving surface smoothing and volume relaxation algorithms on the generated mesh. Mesh Quality Checking: With a set of tools for mesh quality checking, elements with undesirable skewness or angles may be displayed to highlight the block topology region where the individual blocks need to be adjusted.

Replay Option: Replay file functionality enables parametric block topology generation linked to para- metric changes in geometry. Symmetry: As necessary in analyzing rotating machinery applications, for example, Hexa allows you to take advantage of symmetry in meshing a section of the rotating machinery thereby minimizing the model size.

Link Shape: This allows you to link the edge shape to existing deforming edge. This gives better control over the grid specifically in the case of parametric studies. Adjustability: Options to generate 3D surface meshes from the 3D volume mesh and 2D to 3D block topology transformation. Check the Mesh quality to ensure that specified mesh quality criteria are met. If necessary, you may always return to previous steps to manipulate the blocking if the mesh quality does not meet the specified threshold or if the mesh does not capture certain geometry features.

The blocking may be saved at any time, thus allowing you to return to previous block topologies. Unstructured and Multi-block Structured Meshes Additionally, at any point in this process, you can generate the mesh with various projection schemes such as full face projection, edge projection, point projection or no projection at all. Note In the case of no projection, the mesh will be generated on the faces of the block model and may be used to quickly determine if the current blocking strategy is adequate or if it must be modified.

The Hexa Database The Hexa database contains both geometry and block topology data, each containing several sub-en- tities. The geometry is selected in the CAD system and tagged with information made intelligent for grid generation such as boundary conditions and grid sizes and this intelligent geometry information is saved with the master geometry. In Hexa, by updating all entities with the update projection function, blocking vertices projected to prescribed points in the geometry are automatically adapted to the parametric change and one can recalculate the mesh immediately.

Additionally, with the use of its Replay functionality, Hexa provides complete access to previous operations. Unstructured and Multi-block Structured Meshes The mesh output of Hexa can be either unstructured or multi-block structured and need not be determ- ined until after you have finished the whole meshing process when the output option is selected.

Unstructured Mesh Output The unstructured mesh output option will produce a single mesh output file where all common nodes on the block interfaces are merged, independent of the number of blocks in the model. For example, if the block model has 55 blocks, there will be 55 output files created in the output directory. Additionally, without merging any of the nodes at the block interfaces, the Output Block option allows you to minimize the number of output files generated with the multi-block structured approach.

Blocking Strategy With Hexa, the basic steps necessary to generate a hexahedral model are the same, regardless of model complexity. The blocking topology, once initialized, can then be modified by splitting and merging the blocks, as well as through the use of an operation called O-grid Refer to the next section.

While these operations are performed directly on the blocks, the blocks may also go through indirect modific- ation by altering the sub-entities of the blocks i. Upon initialization, Hexa creates one block that encompasses the entire geometry. The subsequent operations under the Blocking menu of developing the block model, referred to as "blocking the geo- metry," may be performed on a single block or across several blocks. Note Note : The topologic entities in Hexa are color-coded based on their properties.

The edge and the associated vertices will be projected to the closest CAD surface between these material volumes.

The vertices of these edges can only move on the surfaces. Blue Edges and Vertices These edges are in the volume. The vertices of these edges, also blue, can be moved by selecting the edge just before it and can be dragged on that edge. Green Edges and Vertices These edges and the associated vertices are being projected to curves. The vertices can only be moved on the curves to which it is being projected. Red Vertices These vertices are projected to prescribed points. Hexa Block Types When blocking a model, it is important to note that the block type affects many operations within Hexa and the entire approach to mesh generation.

For example, if you split a model with mapped blocks, the split will propagate through faces that have a mapped relationship on the opposite side.

For free blocks, a split will terminate at the free face. Similarly, if you set edge parameters on a mapped face edge, opposite edges will have a similar number of nodes.

If however, that edge is attached to a free face, the number of nodes on the opposite side will not be adjusted. Using the Automatic O-grid The ability to convert blocks from free to mapped or vice versa imposes constraints on the blocking and resulting mesh.

By imposing more constraints, you can enforce a greater number of hexa elements, while reducing the constraints can sometimes improve mesh transitioning. Figure: Hexa Block Types Split The Split function, which divides the selected block interactively, may be applied across the entire block or to an individual face or edge of a block by using the Split face or Split edge options, respectively.

Blocks may be isolated using the Index control. Merge The Merge function works similar to split blocks; one can either merge the whole block or merge only a face or an edge of the block. While some models require a high degree of blocking skill to generate the block topology, the block topology tools in Hexa allow you to quickly become proficient in generating a complex block model.

Using the Automatic O-grid The O-grid creation capability is simply the modification of a single block or blocks to a 5 sub-block topology as shown below. There are several variations of the basic O-grid generation technique and the O-grid shown below is created entirely inside the selected block. In Figure , the Add Face option was used on the right most block to add the bottom face on the block prior to generating the O-grid.

Another important feature of the automatic O-grid is the ability to re-scale the O-grid after generation. The Re scale O grid option allows you to re-scale the previously generated O-grid. The blocks may also be modified by moving the vertices of the blocks and by defining specific relation- ships between the faces, edges and vertices to the geometry.

Most Important Features of Hexa Hexa has emerged as the quickest and most comprehensive software for generating large, highly accurate, 3D-geometry based hexahedral meshes.

Now, in the latest version of Hexa, it is also possible to generate 3D surface meshes with the same speed and flexibility. This process would not have been possible without the presence of O-grids. The O-grid technique is utilized to model geometry when the you desire a circular or "O"-type mesh either around a localized geometric feature or globally around an object. The O-grid is then generated either inside or outside the selected blocks.

The O-grid may be fully contained within its selected region, or it may pass through any of the selected block faces. If a value that is less than 1 is assigned, the resulting O-grid will be smaller than the original. If, however, a value is larger than 1, the resulting O-grid will be larger. Edge Meshing Parameters The edge meshing parameter task has been greatly automated by providing you with unlimited flexib- ility in specifying bunching requirements.

Assigning the edge meshing parameters occurs after the de- velopment of the block topology model. Additional tools such as Linked Bunching and the multiple Copy buttons provide you with the ability to quickly apply the specified edge bunching parameters to the entire model. The block topology may be smoothed to improve the block shape prior to mesh generation.

This reduces the time required for development of the block topology model. The geometry and its associative faces, edges, and points are all constraints when smoothing the block topology model.

Once the block topology smoothing has been performed, you may smooth the mesh after specifying the proper edge bunching parameters. Refinement The refinement capability is used for solvers that accept non-conformal node matching at the block boundaries. The refinement capability is used to minimize the model size, while achieving proper mesh definition in critical areas of high gradients. Entering a scale factor greater than 1 will result in refinement. Coarsening In areas of the model where the flow characteristics are such that a coarser mesh definition is adequate, coarsening of the mesh may be appropriate to contain model size.

Entering a scale factor less than 1 will result in coarsening. Changes in length, width and height of specific geometry features are categorized as parametric changes. These changes do not, however, affect the block topology. Therefore, the Replay function is capable of automatically generating a topologically similar block model that can be used for the parametric changes in geometry. You can also use variables in the replay script to parametrize edge parameters.

Generating a Replay File The first step in generating a Replay file is to activate the recording of the commands needed to gen- erate the initial block topology model.

All of the steps in the mesh development process are recorded, including blocking, mesh size, edge meshing, boundary condition definition, and final mesh generation. The next step in the process is to make the parametric change in the geometry and then replay the recorded file on the changed geometry.

All steps in the mesh generation process are automated from this point. Advantage of the Replay Function With the Replay option, you may analyze more geometry variations, thus obtaining more information on the critical design parameters. This can yield optimal design recommendations within the project time limits. Additionally, he has interested in Product Design, Animation, and Project design.

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