GiD 10.0 user manual

PRESENTATION OF GiD

This chapter will introduce the user to the user-interface and graphic environment of GiD.

GiD is a general purpose pre-postprocessor for computer analysis.

All the data, geometry and mesh generation can be performed inside. Also, the visualization of all types of results can be performed....

User interface

Upon opening GiD, the following window appears on the screen:

To change the configuration of toolbars and menus, use the toolbars option, located in Utilities->Tools->Toolbars.

Top menu

The Top Menu offers various types of commands.

It is important to note that these options will differ depending on the whether the user is performing a preprocessing or postprocessing analysis, and that the options needed in each case differ as well.

Two possible configurations of the Top Menu are presented below:

And in the postprocessing phase:...

Files-Pre

Two main types of functions can be controlled in this menu: 1) the handling of files (i.e. create, read, save, etc.) of GiD projects;and, 2) the importing and exporting of files.

View

In the view menu (also available from the mouse menu) there are all the visualization commands. These commands change the way to display the information in the graphical window, but they do not change any definition of the geometry or any other data.

Geometry permits the user to create, delete, edit and model geometry.

Utilities.Pre

In the Utilities menu, GiD allows the user to define preferences or perform operations on both the geometry and the mesh entities.

Data

This menu allows access to the definition of all data related to materials, boundary conditions, etc., which will be necessary for the calculations that follow. The form of this data will depend on the type of the analysis to be performed.

Mesh

Mesh permits the user to generate and edit the mesh, as well as to select mesh creation preferences.

Calculate

This command calculates the problem, according to the type of problem defined. This option requires a previously activated interface between GiD and the corresponding calculation program.

Help

This menu permits the user to obtain different types of help and information about GiD.

Files

GID PostProcess

This Top Menu of the postprocess phase is the same of that as the preprocess phase and has the same name. The user can read and save files, save screen images, return to preprocess phase options and exit the program.

Utilities

In the postprocess phase, the Utilities command permits the user to obtain information about entities.

Do cuts

With the option Do cuts the user can make cuts through entities.

View results

This option permits the user to choose the viewing type in which the results of the postprocess calculation will be presented.

Options permit the user to make choices related to the presentation of results: for example, color changes, number of result subdivisions, etc.

Postprocess windows

Toolbars

Option Utilities->Tools->Toolbars... opens a window where it’s possible to configure the toolbars position or switch them on and off.

Geometry and View operations

(preprocess)

Standard toolbar

...

Mouse menu

The Mouse Menu is the auxiliary menu which appears by clicking on the right mouse button while the cursor is over the GiD screen.

The Mouse Menu permits the user to quickly access various image placement and viewing commands, to facilitate easy management and definition of the project.

Furthermore, the Mouse Menu contains the Contextual menu, which permits the user to access to all options available in previously performed commands. The option Contextual is only available after the user has performed a command from the ...

Command line

The Command Line option allows the user to directly enter all executable GiD commands, without accessing the commands through drop-down menus.

These commands should be written following the order which GiD would use to define them, according to the Right buttons menus.

A side comment in reference to the Command Line...

INITIATION TO GiD

With this example, the user is introduced to the basic tools for the creation of geometric entities and mesh generation.

First steps

Before presenting all the possibilities that GiD offers, we will present a simple example that will introduce and familiarize the user with the GiD program.

The example will develop a finite element problem in one of its principal phases, the preprocess, and will include the consequent data and parameter description of the problem. This example introduces creation, manipulation and meshing of the geometrical entities used in GiD.

First, we will create a line and the mesh corresponding to the line. Next, we will save the project and it will be described in the...

Creation and meshing of a line

We will begin the example creating a line by defining its origin and end points, points 1 and 2 in the following figure, whose coordinates are (0,0,0) and (10,0,0) respectively.

It is important to note that in creating and working with geometric entities, GiD follows the following hierarchical order: point, line, surface, and volume.

To begin working with the program, open GiD, and a new ...

Creation and meshing of a surface

We will now continue with the creation and meshing of a surface.

First, we will create a second line between points 1 and 3.

We will now generate the second line. We will now use again the Coordinates Window to enter the points. (Utilities->ToolsCoordinates-> Window)

Select the line creation tool in the toolbar. Enter point (0,10,0) in the ...

Creation and meshing of a volume

We will now present a study of entities of volume. To illustrate this, a cube and a volume mesh will be generated.

Without leaving the project, save the work done up to now by choosing Files->Save, and return to the geometry last created by choosing Geometry->View geometry.

In order to create a volume from the existing geometry, firstly we must create a point that will define the height of the cube. This will be point 5 with coordinates (0,0,10), superimposed on point 1. To view the new point, we must rotate the figure by selecting from the ...

2D TOOLS, BASIC 3D TOOLS AND MESHING

IMPLEMENTING A MECHANICAL PART

The objective of this case study is implementing a mechanical part in order to study it through meshing analysis. The development of the model consists of the following steps:

• Creating a profile of the part

• Generating a volume defined by the profile

Working by layers

Defining the layers

A geometric representation is composed of four types of entities, namely points, lines, surfaces, and volumes.

A layer is a grouping of entities. Defining layers in computer-aided design allows us to work collectively with all the entities in one layer.

The creation of a profile of the mechanical part in our case study will be carried out with the help of auxiliary lines. Two layers will be defined in order to prevent these lines from appearing in the final drawing. The lines that define the profile will be assigned to one of the layers, called the "profile" layer, while the auxiliary lines will be assigned to the other layer, called the "aux" layer. When the design of the part has been completed, the entities in the "aux" layer will be erased....

Creating two new layers

Creating a profile

In our case, the profile consists of various teeth. Begin by drawing one of these teeth, which will be copied later to obtain the entire profile.

Creating a size-55 auxiliary line

Dividing the auxiliary line near "point" (coordinates (40, 0) )

Creating a 3.8-radius circle around point (40, 0)

Rotating the circle -3 degrees around a point

Rotating the circle 36 degrees around a point and copying it.

...

Rotating and copying the auxiliary lines

Intersecting lines

Creating an arc tangential to two lines

...

Translating the definitive lines to the "profile" layer

Deleting the "aux" layer

Rotating and obtaining the final profile

Creating a surface

Creating a hole in the part

In the previous sections we drew the profile of the part and we created the surface. In this section we will make a hole, an octagon with a radius of 10 units, in the surface of the part. First we will draw the octagon.

Creating a hole in the surface of the mechanical part

Creating volumes from surfaces

The mechanical part to be constructed is composed of two volumes: the volume of the wheel (defined by the profile), and the volume of the axle, which is a prism with an octagonal base that fits into the hole in the wheel. Creating this prism will be the first step of this stage. It will be created in a new layer that we will name "prism".

Creating the "prism" layer and translating the octagon to this layer

Creating the volume of the prism

Creating the volume of the wheel

Generating the mesh

Now that the part has been drawn and the volumes created, the mesh may be generated. First we will generate a simple mesh by default.

Depending on the form of the entity to be meshed, GiD performs an automatic correction of the element size. This correction option, which by default is activated, may be modified in the Meshing card of the Preferences window, under the option Automatic correct sizes. Automatic correction is sometimes not sufficient. In such cases, it must be indicated where a more precise mesh is needed. Thus, in this example, we will increase the concentration of elements along the profile of the wheel by following two methods: 1) assigning element sizes around points, and 2) assigning element sizes around lines....

Generating the mesh by default

Generating the mesh with assignment of size around points

Generating the mesh with assignment of size around lines

Optimizing the design of the part

The part we have designed can be optimized, thus achieving a more efficient product. Given that the part will rotate clockwise, reshaping the upper part of the teeth could reduce the weight of the part as well as increase its resistance. We could also modify the profile of the hole in order to increase resistance in zones under axle pressure.

To carry out these optimizations, we will use new tools such as NURBS lines. The final steps in this process will be generating a mesh and visualizing the changes made relative to the previous design.

This example begins with a file named "optimizacion.gid"....

Modifying the profile

Modifying the profile of the hole

Creating the volume of the new design

Repeat the same process as in section 4.3:

Generating the mesh for the new design

Generating the mesh for the optimized design is more complex. In this geometry it is especially important to obtain a precise mesh on the surfaces around the hole and on the surfaces of the teeth.

Initially, we will generate a simple mesh by default. Then we will generate a mesh using Chordal Error⁶ to obtain a more accurate result.

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⁶ The Chordal Error is the distance between each element generated by the meshing process and the real profile. ...

Generating a mesh for the new design by default

Generating a mesh using "Chordal Error"

ADVANCED 2D & 3D TECHNIQUES AND MESHING

IMPLEMENTING A COOLING PIPE

This case study shows the modeling of a more complex piece and concludes with a detailed explanation of the corresponding meshing process. The piece is a cooling pipe composed of two sections forming a 60-degree angle.

The modeling process consists of four steps:

• Modeling the main pipes

• Modeling the elbow between the two main pipes, using a different file...

Working by layers

Various auxiliary lines will be needed in order to draw the part. Since these auxiliary lines must not appear in the final drawing, they will be in a different layer from the one used for the finished model.

Creating two new layers

Creating the auxiliary lines

The auxiliary lines used in this project are those that make it possible to determine the center of rotation and the tangential center, which will be used later to create the model.

Creating the axes

Creating the tangential center

Creating a component part

In this section the entire model, except the T junction, will be created. The model to be created is composed of two pipes forming a 60-degree angle. To start with, the first pipe will be created. This pipe will then be rotated to create the second pipe.

Creating the profile

Creating the volume by revolution

Creating the union of the main pipes

Rotating the main pipe

Creating the end of the pipe

Creating the T junction

Now, an intersection composed of two pipe sections will be created in a separate file and the surfaces will be trimmed. Then this file will be imported to the original model to create the entire piece.

Creating one of the pipe sections

Creating the other pipe section

Creating the lines of intersection

...

Deleting surfaces and lines

...

Closing the volume

...

Importing the T junction to the main file

The two parts of the model have been drawn. Now they must be joined so that the final volume may be created and a mesh of the volume may be generated.

Importing a GiD file

Creating the final volume

Generating the mesh

Now that the model is finished, it is ready to be meshed. The mesh will be generated using Chordal Error in order to achieve greater accuracy in the discretization of the geometry. The chordal error is the distance between the element generated by the meshing process and the real profile of the model. By selecting a sufficiently small chordal error, the elements will be smaller in the zones with greater curvature.

Generating the mesh using Chordal Error

Generating the mesh by assignment of sizes on surfaces

ASSIGNING SIZES TO THE ELEMENTS OF A MESH

The objective of this example is to mesh a mechanical piece using the various options in GiD for assigning sizes to elements, and the different surface meshers available. In this example a mesh is generated for each of the following methods for assigning sizes, using different surface meshers:

• Assigning sizes around points

• Assigning sizes around lines

Introduction

In order to carry out this example, start by opening the project “ToMesh4.gid”. This project contains a geometry that will be meshed using four different methods, each one resulting in a different density of elements in certain zones.

Reading the initial project

• In the Files menu, select Read . Select the project “ToMesh4.gid” and click Open.

• The geometry appears on the screen. It is a set of surfaces.

• Select Render->Flat from the mouse menu¹.

• Select Rotate->Trackball from the mouse menu. (This tool is also available within the GiD Toolbox.) Make several changes in the perspective so as to get a good idea of the geometry of the object.

• Finally, return to the normal visualization, selecting ...

Element-size assignment methods

GiD automatically corrects element sizes according to the shape of the entity to be meshed and its surrounding entities. This default option may be deactivated and reactivated by going to the Mesh menu, selecting Preferences², and then Automatic correct sizes³.

Sometimes, however, this type of correction is not sufficient and it is necessary to indicate where on the mesh greater accuracy is needed. In these cases, GiD offers various options and methods allowing sizes to be assigned to elements....

Assignment using default options

...

Assignment around points

Assignment around lines

Assignment on surfaces

Assignment with Maximum Chordal Error

Rjump mesher

The RJump mesher is a surface mesher that meshes patches of surfaces (in 3D space) and is able to skip the inner lines of these patches when meshing. By default, the RJump mesher skips the contact lines between surfaces that are tangent enough, and points between lines that are tangent enough. By selecting Mesh->Draw->Skip entities (Rjump), the entities that RJump is going to skip and the ones that it is not going to skip are displayed in different colors. In this chapter we will see the properties of this mesher.

RJump default options

Force to mesh some entity

If there is a line or a point that the RJump mesher would usually skip, but that you wish to be meshed, you can specify the entity so that it is not skipped. As an example, we will force Rjump to mesh line number 43, in order to concentrate elements around point number 29, as it was done in chapter 2.2.

METHODS FOR MESH GENERATION

The objective of this example is to mesh a model using the various options available in GiD for controlling the element type in structured, semi-structured and unstructured meshes. It also presents how to concentrate elements and control the distribution of mesh sizes.

The six methods covered are:

• Generating a mesh using tetrahedral

• Generating a volume mesh using spheres

• Generate a mesh using circles

• Generating a volume mesh using points

• Generating a mesh using quadrilaterals

• Generating a structured mesh on surfaces and volumes ...

Introduction

In order to carry out this example, start from the project "ToMesh3.gid". This project contains a geometry that will be meshed using different types of elements.

Reading the initial project

Types of mesh

Using GiD the mesh may be generated in different ways, depending on the needs of each project. The two basic types of meshes are the structured² mesh and the unstructured mesh. For volumes only there is one additional type, the semi-structured³ mesh.

For all these types of mesh a variety of elements may be used (linear ones, triangles, quadrilaterals, circles,tetrahedra, hexahedra, prisms, spheres or points). In this tutorial you will become familiarized with the mesh-generating combinations available in GiD.

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Generating the mesh by default

Generating the mesh using circles and spheres

Generating the mesh using points

Generating the mesh using quadrilaterals

Generating a structured mesh (surfaces)

Generating structured meshes (volumes)

Generating semi-structured meshes (volumes)

Concentrating elements and assigning sizes

Generating the mesh using quadratic elements

Select Zoom->In from the mouse menu (this option may also be found in the GiD Toolbox or in the View menu). Enlarge one area of the mesh (e.g. the zone near point number 3).

POSTPROCESSING

The objective of this tutorial is to do a postprocess analysis of an already calculated fluid simulations, no preprocess option is used.

Not only the model is already meshed and the constraints are assigned, but also the results have been calculated. For more information about the preprocess part of GiD, please check the preprocess tutorials.

In this tutorial, the model Cylinder.bin has been used. The problem type used to do this simulations is Tdyn, particularly the Ransol model. Tdyn is a fluid dynamic (CFD) simulation environment based on the stabilized Finite Element Method.

...

Loading the model

There are two ways to load the results simulation information into GiD:

• If the model has been calculated inside GiD, and so the results are inside a GiD project, then just loading the GiD project and the changing to postprocess mode is enough. This can be achieved clicking on this icon:

, or selecting the Files->Postprocess menu entry.

• If only a mesh and results file(s) is present then GiD should be started, and switched to postprocess mode (...

Changing mesh styles

Through the 'Select & Display style' window several options can be specified for volumes, surfaces and cuts. Among these options volumes, surfaces and cuts can be switched on and off, their colour properties can be changed, and their transparency too.

Other interesting options which can be changed are the style of the set and the width of the edges.

From this window, volumes, surfaces or cuts can be deleted or their names can be modified.

To access this windows select Windows->View Style or Utilities->View style...

Viewing the results

Several results had been calculated for several time steps. You can check these results through the Results menu or opening the View Results window.

Menu:View Results

Window->View Results...

Menu: View results->Iso Surfaces

With this result visualization a surface, or line, is drawn passing through all the points which have the same result's value inside a volume mesh, or surface mesh. To create isosurfaces there are several options.

. Select View results->Iso Surfaces->Automatic Width->Velocity(m/s)->|V|throught the menu bar or clicking on

After choosing the result, you are asked for a width. This width is used to create as many isosurfaces as are needed between the Minimum and Maximum defined values (these are included). ...

Menu:Window->Animate...

This window allows the user to animate the current visualized results.

If only one step is present, then the Static analysis animation profile button is enabled so that a custom animation profile can be step to animate that one step.

If one result has several steps you can visualize them in an animation. In this case we will use the iso surfaces result.

Result surface

Another result visualization of interest is this one:

To get this visualization follow these steps:

Contour fill

Menu: View results->Contour Fill

. Please select View results->Contour Fill->Pressure (Pa)through the menu bar, or clicking on or using the Window->View results......

Combined results

An interesting postprocess options is to combine several result visualizations, like this one:

To get this view follow these steps:

. Clear all results visualizations with View Results->No results or the icon ...

Menu: View->Advanced options...

If you have an anaglyphic glasses you can try this option. The model can be set as an anaglyphic image in order to provide a stereoscopic 3D effect, when viewed with 2 color glasses (each lens a chromatically opposite color, usually red and cyan).

Anaglyphic images are made up of two color layers, superimposed. Since the glasses act as red and cyan filters we should be careful with the model's colors. To avoid problmes we will change the contour fill color scale....

Menu: View results->Show Min Max

With this option you can see the minimum and maximum value of the chosen result in the chosen analysis step. In our case we will choose the Vy component of velocity result for the first analysis step.

. Select View results->Default Analysis/Step->RANSOL->91.5 throught the menu bar or clicking on

Menu: View results->Stream Lines

With this option you can display a stream line, or in fluid dynamics, a particle tracing, in a vector field.

. Select View results->Stream Lines->Velocity (m/s) throught the menu bar or clicking on ...

Menu: View results->Graphs

From this menu several graphs types can be created, we will try some of them. Graphs are supported for results defined over nodes.

The Point evolution graph displays a graph of the evolution of the selected result along all the steps, of the default analysis, for the selected nodes.

Menu:Files->Page and capture settings...

Finally we will take some snapshots of our model. You can save images in several formats. The properties of the image (resolution, size, etc.) can be assigned in Page and capture settings option.

IMPORTING FILES

IMPORTING FILES

The objective of this case study is to see how GiD imports files created with other programs. The imported geometry may contain imperfections that must be corrected before generating the mesh.

For this study an IGES formatted geometry representing a stamping die is imported. These steps are followed:

• Importing an IGES-formatted file to GiD

• Correcting errors in the imported geometry and generating the mesh

• Generating a conformal mesh and a non-conformal mesh

...

Importing on GiD

GiD is designed to import a variety of file formats. Among them are standard formats such as IGES, DXF, or VDA, which are generated by most CAD programs. GiD can also import meshes generated by other programs, e.g. in NASTRAN or STL formats.

The file importing process is not always error-free. Sometimes the original file has incompatibilities with the format required by GiD. These incompatibilities must be overcome manually. This example deals with various solutions to the difficulties that may arise during the importing process....

Importing an IGES file

Correcting errors in the imported geometry

The great diversity of versions, formats, and programs frequently results in differences (errors) between the original and the imported geometry. With GiD these differences might give rise to imperfect meshes or prevent meshing altogether. In this section we will see how to detect errors in the imported geometry and how to correct them.

Importing the same file with different versions of GiD might produce slight variations in the results. For this tutorial it's necessary load the project "imported48.gid", which contains the original IGES file translated into GiD format.

Meshing by default

A window comes up in which to enter the maximum element size for the mesh to be generated. Leave the default value provided by GiD unaltered and click OK.

When the GiD finishes the meshing process, an error message appears (see Figure 6). This error is due to a defect in the imported geometry. As the window shows, there have been errors meshing surface number 149.

...

Correcting surfaces

The conformal mesh and the non-conformal mesh

In the previous section, after correcting some errors, we were able to mesh the imported geometry, thus obtaining a non-conformal mesh. A conformal mesh is one in which the elements share nodes and sides. To achieve this condition, contiguous surfaces (of the piece) must share lines and points of the mesh. Most calculating modules require conformal meshes; however, some modules accept non-conformal meshes. A non-conformal mesh normally requires less computation time since it generates fewer elements.

Global collapse of the model

Correcting surfaces and creating a conformal mesh

Select View->Mode->Geometry to visualize the geometry of the piece.

...

NOTE: Non-conformal meshes may be used with some calculating modules, i.e. stamping a plate. Using non-conformal meshes significantly reduces the number of elements in the mesh. This cuts down on computation time.

NOTE: By using Chordal Error, the geometry may be discretized with great precision. The chordal error is the distance between the elements generated by the meshing program and the profile of the real object. Entering a sufficiently small chordal error results in small elements in zones where there is greater curvature. Accordingly, the approximation of the mesh may be improved in zones with greater curvature by using the option "Chordal Error."

"Chordal Error" generates an increased number of elements in zones where there is curvature. One way of obtaining accurate meshes with few elements is using structured elements in zones where there is curvature. The option ...

DEFINING A PROBLEM TYPE

This tutorial takes you through the steps involved in defining a problem type using GiD. A problem type is a set of files configured by a solver developer so that the program can prepare data to be analyzed.

A simple example has been chosen which takes us through all the associated configuration files while using few lines of code. Particular emphasis is given to the calculation of the centers of mass for two-dimensional surfaces  a simple formulation both conceptually and numerically.

The tutorial is composed of the following steps:

Starting the ‘problemtype’...

Introduction

Our aim is to solve a problem that involves calculating the center of gravity (center of mass) of a 2D object. To do this, we need to develop a calculating module that can interact with GiD.

The problem: calculate the center of mass.

The center of mass (X_CM,Y_CM) of a two-dimensional body is defined as

Interaction of GiD with the calculating module

GiD Preprocess makes a discretization of the object under study and generates a mesh of elements, each one of which is assigned a material and some conditions. This preprocessing information in GiD (mesh, materials, and conditions) enables the calculating module to generate results. For the present example, the calculating module will find the distance of each element relative to the center of mass of the object.

Finally, the results generated by the calculating module will be read and visualized in GiD Post-process.

...

Implementation

Creating the Subdirectory for the Problem Type

Create the subdirectory "cmas2d.gid". This subdirectory has a .gid extension and will contain all the configuration files and calculating module files (.prb, .mat, .cnd, .bas, .bat, .exe).

NOTE: If you want the problem type to appear in the GiD Data→Problem type menu, create the subdirectory within "problemtypes", located in the GiD folder  for instance, C:GiDProblemtypescmas2d.gid

Creating the Materials File

Create the materials file "cmas2d.mat". This file stores the physical properties of the material under study for the problem type. In this case, defining the density will be enough.

Enter the materials in the "cmas2d.mat" file using the following format:

MATERIAL: Name of the material (without spaces)

QUESTION: Property of the material. For this example, we are interested in the density of the material.

VALUE: Value of the property...

Creating the General File

Create the "cmas2d.prb" file. This file contains general information for the calculating module, such as the units system for the problem, or the type of resolution algorithm chosen.

Enter the parameters of the general conditions in "cmas2d.prb" using the following format:

PROBLEM DATA

QUESTION: Name of the parameter. If the name is followed by the #CB# instruction, the parameter is displayed as a combo box. The options in the menu must then be entered between parentheses and separated by commas....

Creating the Conditions File

Create the "cmas2d.cnd" file, which specifies the boundary and/or load conditions of the problem type in question. In the present case, this file is where the concentrated weights on specific points of the geometry are indicated.

Enter the boundary conditions using the following format:

CONDITION: Name of the condition

CONDTYPE: Type of entity which the condition is to be applied to. This includes the parameters "over points", "over lines", "over surfaces", “over volumes” or "over layers". In this example the condition is applied "over points”....

Creating the Data Format File (Template file)

Create the "cmas2d.bas" file. This file will define the format of the .dat text file created by GiD. It will store the geometric and physical data of the problem. The .dat file will be the input to the calculating module.

NOTE: It is not necessary to have all the information registered in only one .bas file. Each .bas file has a corresponding .dat file.

Write the "cmas2d.bas" file as follows:

The format of the .bas file is based on commands. Text not preceded by an asterisk is reproduced exactly the same in the .dat file created by GiD. A text preceded by an asterisk is interpreted as a command....

Creating the Execution file of the Calculating Module

Create the file "cmas2d.c". This file contains the code for the execution program of the calculating module. This execution program reads the problem data provided by GiD, calculates the coordinates of the center of mass of the object and the distance between each element and this point. These results are saved in a text file with the extension .post.res.

Compile and link the "cmas2d.c" file in order to obtain the executable cmas2d.exe file.

The calculating module (cmas2d.exe) reads and generates the files described below.

Creating the Execution File for the Problem Type

Create the "cmas2d.win.bat" file. This file connects the data file(s) (.dat) to the calculating module (the cmas2d.exe program). When the GiD Calculate option is selected, it executes the .bat file for the problem type selected.

When GiD executes the .bat file, it transfers three parameters in the following way:

(parameter 3) / *.bat (parameter 2) / (parameter 1)

parameter 1: project name

parameter 2: project directory

Using the problemtype with an example

In order to understand the way the calculating module works, simple problems with limited practical use have been chosen. Although these problems do not exemplify the full potential of the GiD program, the user may intuit their answers and, therefore, compare the predicted results with those obtained in the simulations.

Create a surface, for example from the menu Geometry->Create->Object->Polygon

Create a polygon with 5 sides, centered in the (0,0,0) and located in the XY plane (normal = 0,0,1) and whit radius=1.0

Executing the calculation with a concentrated weight

Executing the calculation for an object of heterogeneous material and subject to external point-weight

Choose the Files→preprocess option (to go back to preprocess).

Choose the Data→Conditions option. A window is opened in which the conditions of the problem should be entered.

Since the condition to be entered acts over points, select over points from the Type menu in the Conditions window.

NOTE: In this example, a code for the program will be developed in C. Nevertheless, any programming language may be used.

The code of the program that calculates the center of mass (cmas2d.c) is as follows:

The cmas2d.c file

The main program

The main program is called from the cmas2d.win.bat file and has as parameter the name of the project. This name is stored in the variable projname.

The main program calls the input (), calculate () and output () functions.

The input function reads the .dat file generated by GiD. The .dat file contains information about the mesh. The calculate function read and processes the data and generates the results. The output function creates the results file.

void input () {

char filename[1024], fileerr[1024], sau1[1024], sau2[1024];...