This website uses cookies to function and to improve your experience. By continuing to use our site, you agree to our use of cookies. When setting up your simulation, you can use selections to represent different parts of your geometry. This can be helpful in many instances, such as when you are specifying materials, applying boundary conditions, customizing the mesh, and more.

All of the following 2014 gmc yukon xl types use previously defined selections as input. Difference selections — create selections of entities that are in one selection, but not another. If you want to create selections of geometric entities that are touching other selections, use adjacent selections. You also have the option to select exterior or interior entities with this selection type.

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Overview Transcript Application Files Share:. Boolean selections include: Complement selections — create selections that are the inverse of one or more selections Difference selections — create selections of entities that are in one selection, but not another Union selections — combine two or more selections into a single one Intersection selections — create selections of entities contained in all input selections If you want to create selections of geometric entities that are touching other selections, use adjacent selections.

Related Videos. Deep Excavation Simulation Tutorial. Log Out.One such tool, Partition Operations, enables you to separate out any part of your model's geometry.

This is useful for splitting geometric entities such as objects, domains, boundaries, and edges and for removing parts of your model's geometry, either to clean it up or to simplify the model. In addition, this functionality is helpful for when you want to improve a model's mesh as well as when you are working with a geometry that is complex or has parts exhibiting a high aspect ratio. In this video, we discuss how to partition a geometry with work planes using two examples.

First, using a helix primitive object, we show you how to divide and conquer the meshing for a relatively complex geometry by splitting it into smaller, simpler domains. Next, using the geometry from the shell-and-tube heat exchanger tutorial modelwe demonstrate exploiting the symmetry of an object to simplify a simulation. This is done by splitting and then removing one half of the geometry using the Partition Objects and Delete Entities operations, respectively.

As a result, you can significantly reduce the computational time and memory required to solve the model. Learn more about how partitioning can help you mesh and simplify your model by reading the following blog posts:.

### Creating a Model Geometry in COMSOL Multiphysics®

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Overview Transcript Application Files Share:. Learn more about how partitioning can help you mesh and simplify your model by reading the following blog posts: Improving Your Meshing with Partitioning Improving Your Meshing with Swept Meshes.

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### Geometry Modeling in Simulation Apps

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I'm attempting to model Joule heating in a metallic object immersed in a saline slurry. I've created the slurry object and assigned material properties to it. I've also imported a CAD model of the metallic object an hip prosthesis. I'm assuming that I must do some kind of Boolean difference of the object and the liquid slurry before proceeding.

Hi when you leave the geoemtry node, COMSOL does "ana analyse" of the geoemtry and transform the "objects" what I call volumes faces, lines and points" and into "entities" Dmains, boundaries, edges, points If you work in "union mode" finish node then COMSOl will make two domains, your metallic part and the surrounding volume difference of overlapping volumes In "assembly" mode nothing to do with a CAD assembly be aware ; the volumes will overlap, then you must do the union, difference etc yourself before leaving the Geomtry node This is very important concept and methodology steps of COMSOL to understand, as COMSOl differs from other "older" FEM tools here.

Thank you for the prompts response! To be clear, when you speak of working in "Union mode", what exactly does that mean? Do I performa boolean union of the part and the slurry? Hi check the doc aboit the "geoemtry". Thank you again. I discovered this after posting my question to you yesterday and was able to make more progress in the modeling.

I'm now dealing with meshing issues in the hip implant model imported from another CAD program, but this is another problem altogether! Cheers, David. Log Out.This website uses cookies to function and to improve your experience. By continuing to use our site, you agree to our use of cookies. A COMSOL application allows easy access to not only parameterized models but also completely different geometry configurations, such as a mixer with a variable number of impeller blades or a variable number of impellers.

To make this easy for the application developer, we have made available cumulative selections and geometry parts. See how these tools work. Instead, we need tools that automatically update these operations behind the scenes.

Cumulative selections will help us with this — they are used to group geometric entities such as domains, boundaries, edges, and points. For example, when a parameter value is changed, the geometry model may change in such a way that splits a boundary. What was once a single boundary may now be split in two or more parts.

If the boundary condition is tied to a cumulative selection, then this tells the application what new boundary condition to apply to the newly created boundaries. Cumulative selections are also used to update material properties, other physics settings e. For example, different domains created in different geometry operations can be gathered in the geometry sequence according to the material of the domains.

That way, all domains with the same material are available in a single cumulative selection. The assignment of a material to such a selection can be updated automatically when domains are added or removed in the geometry sequence during a parameterization. These include the creation of a block or spheres, Boolean unions, intersections, or more high-level operations, such as fillet and loft.

This sequence of operations is referred to as the geometry sequence. Cumulative selections can also be used within the geometry sequence for pure geometry modeling tasks. For instance, a cumulative selection can gather objects to be added or subtracted in a Boolean difference operation, see the figure below. The difference operation is then automatically updated even in the case where the number of objects to be subtracted changes.

Geometry parts can be viewed as custom composite geometry objects. They can be used in a geometry sequence in the same way as primitive objects like blocks and spheres. Geometry parts are defined globally for a model and can be added to the geometry sequence of any model component as part instances. A geometry part can receive model parameters as input. The output is one or several geometry objects and one or several selections that can be used as input selections by geometry operations and the material, physics, mesh, and results settings.

Geometry parts can use cumulative selections internally within the geometry sequence that builds the part, but they can also contribute with their output selections to cumulative selections in the main geometry sequence when a part instance is added. Cumulative selections and geometry parts are important concepts in the ability to create applications that use parameterized geometries.

In fact, the geometry parts and the cumulative selections were both built with the Application Builder and the creation of apps in mind. The geometry sequence, represented in the geometry branch in the model tree, is based on primitive objects — such as cylinders and blocks — and composite objects — such as objects that are a result of a Boolean operation or a sweep of a cross-sectional profile.

Operations that create composite objects may require selections as input. For example, the difference operation between two groups of objects requires that the two object groups in question are specified in a selection list. In the figure below, the Tank selection includes one object created by part instance 1 pi1. In this case, we want to subtract the impeller shaft and the different impellers from the tank to create the remaining object that corresponds to the fluid domain in the tank.

Three impellers imp1 to imp3 and one shaft pi2 are the objects in the Impeller input selection. Also, selections and cumulative selections may be used as input to populate the list of objects.

Cumulative selections make it possible to organize this process and to automatically update geometry operations that require input selections created in previous operations. We can exemplify the use of cumulative selections in the geometry sequence that creates a Rushton impeller. A Rushton impeller consists of a number of impeller blades attached to a disk with an impeller hub that can be attached to the impeller shaft.This website uses cookies to function and to improve your experience.

By continuing to use our site, you agree to our use of cookies. Creating the geometry for your model is one of the first steps of setting up a simulation. These include geometric primitives; Boolean, partition, and transformation operations; work plane operations; and other CAD tools. Here, we highlight all of this functionality and, near the end, link to a video tutorial series that shows how to use them while building your model geometry.

Each of these means of geometry creation provides different opportunities and advantages. Sometimes, it can be more efficient to create geometry primitives in lower dimensions using work planes and then extend them into the dimension that was not initially considered.

Work planes can also be used to define cross sections from a higher dimensional entity to a lower dimensional workspace. One option is to choose an object from the selection of built-in geometric shapes in the software, select and add the primitive object to your geometry sequence, and then edit the template provided through the Settings window. This enables you to specify the exact position, angle, and dimensions of the object as well as to quickly make changes to any of those settings, if needed.

Once in the sequence, the object can then be combined and manipulated with other primitive objects to form your final geometry. The types of objects available for you to choose from depend on the spatial dimension of your component.

This includes geometric primitives for conventional shapes as well as other less traditional shapes. For 3D models, you can add objects like blocks or spheres as well as torus or helix objects.

Another option for generating objects in your geometry sequence, available for 2D and 1D models, is to sketch geometric primitive objects with the mouse. Immediately afterward, the object you have outlined appears and is added to your geometry sequence. For 3D models, although you cannot sketch a geometry primitive with the mouse, you can draw a cross section of it in a work plane, which can then be expanded into a 3D object. We demonstrate both options mentioned above in dedicated chapters within the building 2D geometries part of the video series.

Additionally, we discuss the advantages of using parameters during this process and demonstrate how they aid in streamlining your geometry setup.

## COMSOL Learning Center

After generating a few objects in your geometry sequence, you can start to combine them in meaningful ways using geometry operations.

In the video chapters on building 2D geometries and 3D geometries in our series, we build a rectangular plate containing slots and a grille, respectively. This was done by using a combination of several Boolean and transformation operations. The Boolean operations used to create the geometries pictured above include the UnionIntersectionand Difference operations, which enable you to combine objects, create a new object from the intersection of other objects, and subtract objects from one another, respectively.

Likewise, the transformation operations used include the MoveCopyMirrorand Array operations, which enable you to change the position of objects; create duplicate objects; reflect objects over a plane, line, or point; and create an arrangement of duplicates of another object. Aside from some of the more conventional geometry features used above, there are also specialized geometry tools used to help create certain types of geometries.

Partition operations enable you to split geometric entities such as objects, domains, boundaries, and edges so that you can separate, remove, or simplify the geometry in your model. When we discuss using partition operations for geometries in the video, we demonstrate how to perform this on a helix object as well as the geometry for the shell and tube heat exchanger tutorial model.

A helix geometry split down the middle, from our video chapter on partitioning geometries. Changing the size of one object in the geometry may require other objects to be resized to accommodate that change. For these and other reasons, we encourage the use of parameters in the geometry operations you use in your sequence. We discuss the reasons for this and demonstrate how with a few of the example geometries built throughout the video series.

COMSOL Multiphysics contains several tools known as work plane operations, which can be used to convert a 2D geometry in a work plane into a 3D object. In the video series, we show and demonstrate the ExtrudeRevolveand Sweep operations.

The Extrude operation enables you to extrude objects from a work plane or planar face to create 3D objects. The Extrude operation, converting a rectangular plate with holes into a 3D block containing slots.

The blue arrow in the center represents the direction in which the shape is extended, which is perpendicular to the work plane.This website uses cookies to function and to improve your experience.

By continuing to use our site, you agree to our use of cookies. The information provided may be out of date.

Discussion Closed This discussion was created more than 6 months ago and has been closed. To start a new discussion with a link back to this one, click here. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' or the latest version listed if standards is not an option. North America. Log Out Log In Contact. OK Learn More. Discussion Forum. Forum Home. New Discussion. What's the difference between Form a union and Form an assembly?

Send Private Message Flag post as spam. Please login with a confirmed email address before reporting spam. Send a report to the moderators. What's the meanings of Form a union and Form an assembly? Is it like this? For example, when I creat two circles, and there is no intersection between them, if I choose Form a union, the two circles will become into a single geometry, and if I choose Form an assembly, the two circles will represent two different geometries, i.

Hi read arefully the documentation on Entities and Objects in V4, it's too lon to write it all here. Mostly you use "union" assembly is for contact and specific user physics, but there are far more behind. Take the time its really worth it to understand what Entities are for, and how they are created from the geoemtry -- Good luck Ivar.

Take the time its really worth it to understand what Entities are for, and how they are created from the geoemtry -- Good luck Ivar Thanks Ivar, I'm sorry I cannot find the documentation on Entities and Objects.

Which documentation?This website uses cookies to function and to improve your experience. By continuing to use our site, you agree to our use of cookies. You have reached the end of the Learning Center. Review the topics in the table of contentsor browse Webinars for more great material. We will continuously update the Learning Center with new topics and materials, so be sure to check back often!

One of the first steps to building a model is creating the geometry. This includes a number of built-in objects for commonly used shapes as well as parameters that enable you to define and position objects. You can also create complicated geometries using the Boolean, transformation, and partitioning geometric operations. We demonstrate how to use these tools to help you build your own 3D geometries in this video. Please feel free to follow along with us on your own computer as we add cylinders and blocks; use union and difference Boolean operations; and perform move, array, and mirror transformation operations.

**COMSOL: Construction of 3D Geometry L-6**

We also share best practices and tips that you can use when building your own geometry. You can fix this by pressing 'F12' on your keyboard, Selecting 'Document Mode' and choosing 'standards' or the latest version listed if standards is not an option. North America. Log Out Log In Contact.

OK Learn More. Repeat Create 3D Geometry. Play Partition Geometry. Duration: One of the first steps to building a model is creating the geometry. Create 2D Geometry Use the software's tools to build 2D geometries. Create 3D Geometry Construct 3D objects using the software's tools. Partition Geometry Split geometry to simplify model and improve mesh. Explore Learning Center. Log Out.

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