# Mesh

Source: https://help.sim-flow.com/documentation/panels/mesh
Last updated: 2026-10-14

## Introduction

![img 595423d93c422](https://help.sim-flow.com/documentation/panels/images/mesh/img_595423d93c422.png)

The **Mesh Panel** gives access to options for modifying and manipulating meshes. Here one can modify mesh regions, boundaries and cell zones in the mesh.

## Editing Regions

When a mesh is generated or imported into the program, it is put into the *default* mesh region. The default mesh region will usually be referred to as *Mesh* since most simulations are performed using this specific mesh region.

### Region Context Options

![img 59542485b7ea3](https://help.sim-flow.com/documentation/panels/images/mesh/img_59542485b7ea3.png)

By clicking on the **Options** button, you can display all the context options available for a given mesh region:

- **Check** - performs mesh quality checks and displays a summary in the console
- **Renumber** - performs reordering of the mesh to reduce matrix bandwidth and therefore reduce computation time
- **Scale** - scales mesh region uniformly or non-uniformly
- **Translate** - moves region along a vector
- **Rotate** - rotates mesh around an arbitrary axis
- **Add Cell Zones** - creates cell zone from cells inside specified geometries
- **Refine** - refines cells inside specified geometries
- **Auto Patch** - divides region boundaries on sharp edges
- **Create Dual Mesh** - creates dual mesh from a given mesh
- **Cell Zones to Regions** - moves cell zone to separate mesh sub-region
- **Make sub-region** - converts default region to a named sub-region
- **Make default** - converts sub-region into default mesh region
- **Rename** - changes the name of a named sub-region
- **Delete** - removes a given region

### Checking Mesh Quality

![mesh check](https://help.sim-flow.com/documentation/panels/images/mesh/mesh-check.png)

When you select the **Check** option, the system will gather basic statistics about the mesh quality and print them to the console. If mesh quality is within acceptable bounds, you will see an *OK* printed in the console. However, if there are some problems with the mesh, you will be able to display problematic elements in the graphic window.

### Renumbering Mesh

When you apply the **Renumber** operation, the system will use the [Cuthill-McKee algorithm](https://en.wikipedia.org/wiki/Cuthill%E2%80%93McKee_algorithm) to renumber cells in the mesh in order to improve the structure of the solution matrix. This option is useful for large meshes and applying it more than once to a given mesh will usually not bring any improvements.

### Scaling Mesh

![img 595425369bf41](https://help.sim-flow.com/documentation/panels/images/mesh/img_595425369bf41.png)

Mesh **Scale** requires providing **Scaling Factors** for three directions. If you want to scale the mesh uniformly in all directions, you can enable the **Uniform** checkbox. After you click **Scale**, the operation will proceed.

### Translating Mesh

![img 59542fe00bf40](https://help.sim-flow.com/documentation/panels/images/mesh/img_59542fe00bf40.png)

To perform the **Translate** operation, you need to provide the **Translation Vector** and click the **Translate** button.

### Rotating Mesh

![img 5954300f9d7ed](https://help.sim-flow.com/documentation/panels/images/mesh/img_5954300f9d7ed.png)

To **Rotate** the mesh, you need to specify the **Rotation Axis** and **Rotation Angle** in degrees. When you click **Rotate**, the mesh as well as all vector fields will be rotated.

*Currently, the mesh can only be rotated around the center of the coordinate system.*

### Adding Cell Zones

![img 5954307de87f7](https://help.sim-flow.com/documentation/panels/images/mesh/img_5954307de87f7.png)

The **Add Cell Zones** operation will generate a cell zone from cells inside selected geometries. After you select all the necessary geometries and click **Create Cell Zones**, the system will generate cell zones with names of the respective geometries. If there already exists a cell zone with a given name, it will be replaced.

### Refining Mesh

The **Refine** operation subdivides each cell inside selected geometries. The **Cut Method** option controls how the cells that are not aligned with the global coordinate system should be divided.

![img 595430b7bbd1b](https://help.sim-flow.com/documentation/panels/images/mesh/img_595430b7bbd1b.png)

The **Hex Topology** method is suitable for most applications and will split cells along their local orientation.

![img 595430e0562f7](https://help.sim-flow.com/documentation/panels/images/mesh/img_595430e0562f7.png)

The **Geometry Cut** will divide cells along coordinate system directions irrespective of the cell orientation.

![img 595430e8b807f](https://help.sim-flow.com/documentation/panels/images/mesh/img_595430e8b807f.png)

If you use **Global Coordinate System**, the cutting directions will be aligned with the global coordinate system. You have an option to disable refinement in certain directions. This can be useful for example when doing refinement in a 2D simulation. After you click **Refine**, the new refined mesh will be loaded.

![img 595430f22269c](https://help.sim-flow.com/documentation/panels/images/mesh/img_595430f22269c.png)

Instead of cutting cells along the global coordinate system, you can cut cells along a local coordinate system associated with a boundary. This option is usually useful for refining boundary layers. To set up a local coordinate system, you need to define the **First Local Direction** which should be tangent to a boundary. Then you need to select a boundary for **Normal Direction** and optionally disable refinement in certain local directions.

### Automatically Patch Boundaries

![img 5954315f25bab](https://help.sim-flow.com/documentation/panels/images/mesh/img_5954315f25bab.png)

The **Auto Patch** operation allows you to divide mesh boundaries on sharp boundary edges. When an angle between normal vectors of two boundary faces is greater than the **Split Angle**, the two faces will be put into separate boundary patches. After you click **Patch**, the boundaries of the mesh will be split.

### Creating Dual Mesh

![mesh tetra after dual](https://help.sim-flow.com/documentation/panels/images/mesh/mesh-tetra-after-dual.png)

The **Create Dual Mesh** operation modifies the mesh in such a way that existing cell centers become new nodes and existing nodes become new cell centers. This operation is usually used to convert tetrahedral meshes into polyhedral meshes. Polyhedral meshes usually offer significantly reduced computational time with only minimal reduction in solution accuracy.

![img 595433af7ec64](https://help.sim-flow.com/documentation/panels/images/mesh/img_595433af7ec64.png)

Before you click the **Create Dual Mesh** button, you can specify the **Feature Angle** to specify which sharp corners should be preserved by the operation.

### Converting Cell Zones To Sub-regions

**Cell Zones To Regions** will extract cells from cell zones and create a mesh sub-region with the same name. This operation is often used for imported meshes since the import procedure will put meshes from external formats into the default region.

### Converting Default Region to Sub-region

![img 595436b7d87cd](https://help.sim-flow.com/documentation/panels/images/mesh/img_595436b7d87cd.png)

When you want to convert the default mesh region to a named sub-region using the **Make sub-region** option, you will be prompted to specify a name for a newly created region.

### Converting Sub-region to Default Region

![img 595436f1e5b28](https://help.sim-flow.com/documentation/panels/images/mesh/img_595436f1e5b28.png)

Any mesh sub-region can be made default using the **Make default** option. When there already exists a default region, you will be prompted to choose one of the possible actions. In this situation, you can:

- **Overwrite** - replace the existing default region with the moved region
- **Merge with** - merge the two regions into one
- **Merge with as cell zone** - merge the two regions into a new cell zone
- **Convert to region** - move the existing default region into a new sub-region

### Renaming Mesh Regions

The **Rename** operation can only be applied to non-default regions.

### Deleting Mesh Region

The **Delete** operation can only be applied to non-default regions. Since this operation is irreversible, before it is completed you will be prompted for final confirmation.

## Editing Boundaries

![img 595437c34ac85](https://help.sim-flow.com/documentation/panels/images/mesh/img_595437c34ac85.png)

Current mesh boundaries are displayed in the **Boundaries** list. Using this list, you can perform various operations on individual boundaries:
1 Change the name by double-clicking in the name area
2 Change the type of the boundary
3 Do advanced manipulations using the context options

![image](https://help.sim-flow.com/documentation/panels/images/mesh/img_595437bcf24d7.png)

Boundaries from all regions are put into the list. You can check to which region a given boundary belongs by simply moving the mouse pointer over the boundary name.

### Changing Boundary Type

![mesh boundary type](https://help.sim-flow.com/documentation/panels/images/mesh/mesh-boundary-type.png)

You can change the boundary type simply by clicking on the appropriate icon. Setting the proper boundary type is essential since it determines how other aspects of the simulation, such as boundary conditions, will be set up. You currently can choose one of five boundary types:

- **Patch** - general boundary type, typically used for inlets and outlets
- **Wall** - boundary type that should be used for walls when using turbulence modeling
- **Symmetry** - boundary type necessary for specifying the symmetry boundary condition
- **Empty** - boundary type that informs the solution algorithm that the flow should not be solved in the directions normal to this boundary. This is used to set up 2D and 1D simulations.
- **Wedge** - boundary type that informs the solution algorithm that this is an axis-symmetric simulation.

### Boundary Context Options

![img 5958e15e3f7a7](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e15e3f7a7.png)

When you click the **Options** button or right-click on the boundary name, a context menu with various operations will be displayed:

- **Refine** - simple operation that refines mesh near a boundary by splitting the first layer of cells in contact with the boundary
- **Create Boundary Layer** - advanced operation for adding boundary layer refinement on boundaries
- **Extrude** - operation that extrudes the mesh from a selected boundary
- **Merge** - operation that takes two or more boundaries and merges them into one
- **Extract From** - operation that takes a boundary and one or more geometries and extracts all boundary faces inside the geometries into a separate boundary

In the context menu, there are also operations for creating mesh interfaces that allow for exchanging information between two boundaries:

- **Cyclic** - requires both boundaries to have identical shape and mesh
- **Arbitrary** - requires both boundaries to have identical shape but the mesh does not have to be identical
- **Arbitrarily Coupled** - interface requires partial overlap of the boundaries
- **Periodic** - enables conformal mapping of periodic geometries

#### Refining Cells Near Boundary

![img 5958e2203115c](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e2203115c.png)

The **Refine** operation will split the first layer of cells next to a boundary. This operation can be used as a crude way to create boundary layer refinement.

![img 5958e24515a3a](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e24515a3a.png)

To perform this operation, you need to specify the **Edge Weight**, which is the relative distance from the boundary at which each cell edge should be split. After that just click the **Refine Wall Layer** button.

#### Creating Boundary Layer

![img 5958e34507a4d](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e34507a4d.png)

The **Create Boundary Layer** operation allows you to create a mesh boundary layer on selected boundaries. This operation allows for much more control than the **Refine** operation. It also allows you to apply boundary layer refinement to more than one boundary.

You can mark the **Relative Size** option unchecked if you want the specification of boundary layer thickness to be absolute instead of relative to the cell size. **Layer Definition** controls which layer thickness will be defined: first or final. **Thickness Definition** tells if the thickness is defined by **Total Thickness** or **Expansion Ratio**.

You can also control what minimum size of the boundary layer is allowed. The final control is the **Number of Layers**. When everything is set properly, you can click **Generate** to start the boundary layer generation process. You should be aware that depending on the size of your original mesh, the generation process can take as long as ten minutes.

#### Extrude Boundary

![extrude boundary](https://help.sim-flow.com/documentation/panels/images/mesh/extrude-boundary.png)

**Extrude Boundary** allows you to modify the existing mesh domain. You can extend the volume by extruding a specific boundary. Mesh extrusion is defined by the variable parameters:

- **Number of Layers** - define the number of additional layers
- **Expansion Ratio** - define layers distribution
- **Extrude** - define the direction of extrusion which can be oriented normal to the boundary face or defined by the vector
- **Thickness** - determine the extrusion distance

#### Merging Boundaries

![img 5958e4e748aa0](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e4e748aa0.png)

When you invoke the **Merge** operation, you need to select all the boundaries that you want to combine. When you click **Merge Boundaries**, a new mesh with merged boundaries will be loaded.

#### Extracting Boundaries

![img 5958e53b7556e](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e53b7556e.png)

The **Extract From** operation is enabled only if you have at least one geometry loaded or created. To apply this operation, you will have to select one or more geometries. After you click **Extract**, all faces of a boundary that are located inside any of the selected geometries will be put into a new boundary.

#### Creating Mesh Interfaces

![img 5958e63cbd579](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e63cbd579.png)

You can create a mesh interface by selecting the appropriate option from the boundary context menu. You can also use a quick option by selecting two boundaries in the list and picking a create button that will be displayed in the list title bar.

![img 5958e64b85cc3](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e64b85cc3.png)

After you create an interface, the two boundaries that comprise the interface will be removed from the boundary list and an entry representing the interface will be added to the list.

![img 5958e656e0dcf](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e656e0dcf.png)

When you create an **Arbitrarily Coupled Interface**, two special boundaries will be added to the list. These boundaries represent non-overlapping parts of an interface.

### Editing Mesh Interfaces

Different types of interfaces may require you to specify additional properties, for example, define the transformation between interface sides. For certain interfaces, there are additional operations that you can perform. These operations are accessible from the context menu of the specific interface.

#### Removing Mesh Interface

![img 5958e6f17d065](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e6f17d065.png)

You can remove an existing interface by clicking the **Break Coupling** button. When an interface is removed, the boundaries that comprised the interface will again appear in the boundary list.

#### Synchronizing Cyclic Interface

![img 5958e736a744a](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e736a744a.png)

Cyclic Interfaces impose very strict requirements on the mesh of two boundaries that are being coupled. You need to make sure that the ordering of nodes on each of the boundaries is exactly the same. To do this, you can use the **Synchronize** option available after right-clicking on the interface.

#### Mesh Interface Properties

![img 5958e77ada5d4](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958e77ada5d4.png)

When you select an interface in the list, a panel with properties will be displayed. In this panel, you can change:
**Match Tolerance** specifies the maximum error in node coincidence between boundaries
**Transform** defines the geometrical orientation of boundaries. Here you can select from several options:

- Unknown - boundaries overlap after automatic ordering
- No Ordering - boundaries overlap without automatic ordering
- Rotational - boundaries will overlap after rotation
- Translational - boundaries are separated by some distance

### Editing Cell Zones

![mesh cell zones](https://help.sim-flow.com/documentation/panels/images/mesh/mesh-cell-zones.png)

A Cell Zone is a named set of cells. Cell Zones are usually used to define zonal models such as porosity or rotating reference frames. Cell Zones can be edited in the **Cell Zones** list under the **Cell Zones** tab.

#### Adding Cell Zones

Cell Zones can be created using context options of Mesh Regions.

#### Removing Cell Zones

![img 5958ea63613d8](https://help.sim-flow.com/documentation/panels/images/mesh/img_5958ea63613d8.png)

Cell Zones can be removed using the **Delete** context option available in the list.