Geometry

Introduction

geometry panel

Geometry panel allows users to add, delete and manipulate geometry. All geometries are listed and sorted alphabetically. Editing options are available after selecting a geometry from the list.

Add Geometry

add geometry

New geometry can be added using buttons available in the Add New bar below the Geometries list. There are two available options to add a geometry:

  • Import Geometry

  • Create Geometry

Import Geometry

load geometry

Import Geometry option allows for importing geometry from external formats. Geometry can be prepared in the external CAD software and exported in the one of supported formats. Currently, supported geometry formats are:

  • STL (recommended)

  • OBJ

  • STEP

  • IGES

  • BREP

To import geometry press Import Geometry button and select the file. Newly imported geometry appears on the Geometries list. Icon on the left from the name determines the type of geometry:

  • icon stl STL geometry

  • icon shell Shell (surfaces) geometry

  • icon solid Solid geometry

Imported Geometry Units (only STL geometry)

imported geometry unit

Every geometry format, except STL, stores information about the units in which the geometry was created. For the STL geometry, the unit need to be confirmed during the import operation. Based on the selected unit, the model will be scaled to the base SI unit - meter. If the unit is unknown, the Geometry size preview should help to choose the right one. The Geometry size displays the current overall size of the geometry being imported (or geometries if multiple files are selected).

To define the unit:

  • 1 Select the unit of imported geometry

  • 2 Control the size of the bounding box

  • 3 Confirm with OK button

Create Geometry

create geometry

Three types of primitive geometries can be created directly in SimFlow. These primitive geometries are usually used as tools for marking mesh cells for refinement or custom solution initialization value.

icon box Create Box - creates the cuboid by setting its origin and dimensions in global coordinate system. The Origin defines the coordinate of the first corner of the box. The Dimensions determine the size of the box measured in the direction of the positive axes of the global coordinate system.

add box

icon cylinder Create Cylinder - creates the cylinder geometry by setting its origin and dimensions. The Origin determines the position of the base center. The cylinder Axis is defined by the vector in global coordinate system perpendicular to the base. The size of the cylinder is defined by the Length and Radius.

add cylinder

icon sphere Create Sphere - creates sphere solid geometry. Center defines the location of the sphere and Radius determines its size.

add sphere

Geometry Options

geometry list

After successfully importing or creating a new geometry, the program will add a new entry to the Geometries list. This entry allows users to manipulate and interact with the geometry.

Icon to the right of the name icon options expand the available geometry options. Currently, supported context options are:

  • Hide/Show - changes visibility

  • Rename - allows to change the geometry name

  • Translate - allows to move the geometry

  • Rotate - allows to rotate the geometry around an arbitrary axis

  • Scale - allows to scale geometry

  • Check (STL only) - performs basic checks of the geometry

  • Clean (STL only) - removes baffles, sliver faces, collapse small edges, etc.

  • Split (STL only) - splits geometry into patches along sharp corners

  • Extract Features (STL only) - generates edges on sharp corners

  • Duplicate - creates a new geometry identical to the current

  • Replace - option for replacing current geometry with a new one

  • Delete - deletes the geometry

Select / Deselect

select
  • Select
    To select the geometry move the mouse over an item and click right mouse button RMB. Selected geometry name will be highlighted on gray.

  • Multi-Select
    Hold on the Ctrl key and click on the next items for multi-selection. Select first item, then holding the Shift key click the second item to select all geometries between these two items.

  • Deselect
    To deselect the item, hold Ctrl key and click RMB on the geometry name. To clear the selection press Esc key on the keyboard or click on the free space outside the geometry list.

Hide / Show

hide show options

In SimFlow there is a possibility to hide or show geometries on the 3D graphic window. Each item could be hidden (or shown) using options on the geometries list. To hide or show geometry in a 3D window:

  • 1 Expand the list of options next to the item

  • 2 Select Hide or Show option or

  • 3 Click the Toggle Visibility icon next to the item name

  • 4 The icon of the hidden element will be greyed out

When you click the icon the second time the respective geometry will be shown in the graphic window and the icon will again become colored.

Rename

rename geometry

Geometries default name is associated with the imported file name or created primitives geometry. It is useful to rename the geometry items to be able to better recognize them during further operation. To rename the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Rename

  • 3 Type a new name and approve by clicking Enter key

  • 4 An alternative approach is to double-click on its name and enter a new one

    To reject the changes press Esc key before approving

Be aware that space and others special characters are not allowed. All of them will be replaced by underscore char during the typing e.g.:

car geometry(1) → car_geometry_1_

Translate

translate

Translation is a movement that changes the position of an object. Each body point is transformed from its initial position to its final position using a translation vector. Translation vector is the same for each point of the object. After Translation, the orientation of the body in space is unaltered.

To Translate the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Translate

When you apply Translate operation, a Translate Geometry panel will appear.

translate options

Following options are allowed:

  • 3 Geometries can be added or removed from the transformation list

  • 4 Translation Vector which define the distance by which the geometry will be moved. Vector is defined in global coordinate system

  • 5 To approve the operation click Translate

Multiple Geometries Translation

translate multiselect

To translate multiple geometries there is an alternative approach:

  • 1 Select geometries to translate (holding Ctrl or Shift key select 2 or more components)

  • 2 Select Translate Geometries

Rotate

rotate

Rotation is the circular movement of an object around the axis of rotation. Movement change the item radial orientation relative to a common point - Origin - which lies within the Axis of rotation. Rotation is not available for box primitive geometry.

To rotate the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Rotate

When you apply Rotate operation, a Rotate Geometry panel will appear.

rotate options

Following options are allowed:

  • 3 Geometries can be added or removed from the transformation list

  • 4 Origin - fixed point of the rotation

  • 5 Axis - direction around which the rotation will be performed

  • 6 Angle - angle of the rotation

  • 7 To approve the operation click Rotate

Multiple Geometries Rotation

rotate multiselect

For multi-selection there is an alternative approach to rotate geometries:

  • 1 Select geometries to rotate (holding Ctrl or Shift key select 2 or more components)

  • 2 Select Rotate Geometries

Scale

scale

Scaling is a transformation, in which the coordinates of each point belonging to an object are multiplied by a relevant factor. In a general approach, scaling is to change the size of an object. However, the scaling operation also changes the position of the object in the global coordinate system. Depending on the scaling factors, operation can cause:

  • enlargement - when the scaling factor is larger than 1

  • reduction - when the scaling factor is positive and smaller than 1

  • reflection - when the scaling factor is negative

Scaling factor equal 0 is not allowed (due to it cause projection). Non-uniform scaling changes the shape of the object.

SimFlow uses SI units so the length is defined in meters. If the imported geometry is defined in other units, it is important to scale the model to the meter e.g.: if model is defined in mm, it has to be scaled to the meter uniformly by scaling factor 0.001. Scale is not available for cylinder and sphere primitives.

To scale the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Scale

When you apply Scale operation a Scale Geometry panel will appear.

scale options

Following options are allowed:

  • 3 Geometries can be added or removed from the scale list

  • 4 To scale uniformly check the Uniform option

  • 5 Define Scaling Factors for each of the directions

  • 6 To approve the operation click Scale

Multiple Geometries Scaling

scale multiselect

Scale can be applied to multiple geometries. To scale few geometries at a time:

  • 1 Select geometries to scale (holding Ctrl or Shift key select 2 or more components)

  • 2 Select Scale Geometries

Check

check

Check option is used for checking geometric and topological quality of a surface. Algorithm checks whether each edge connect with exactly two faces and all points are inside the geometry bounding box. Check option is available for imported geometries.

To Check the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Check

  • 3 The Check summary is printed in a Console

check console

Clean

clean

Clean option is dedicated to the STL geometry formats. It fixes the surface by removing baffles, collapsing small edges by removing triangles and converting sliver triangles into split edges by projecting point onto base of triangle. These clean operations are to prepare the geometry for meshing.

To Clean the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Clean

  • 3 The Clean summary is printed in a Console

clean console

Split

split

Split operation allows you to divide faces into smaller parts. This option is available for STL format where imported geometry is usually a single face and you have to define different boundary conditions on different faces. Splitting geometry will separate faces based on the limit angle between them.

To Split geometry faces:

  • 1 Expand the list of options next to the item

  • 2 Select Split

split options

When you apply Split operation to a geometry a Split Geometry panel will appear with the following options:

  • 3 Split Angle - whenever angle between two STL triangles \(\alpha\) (picture below) is smaller than this value the two triangles will be put into separate faces. Characteristic values of the split angle:

    • 0 degrees - no edges selected

    • 180 degrees - all edges selected

    • 120 degrees - default angle

split angle
  • 4 Remove After Split - input to specify whether the original unsplit geometry should be removed after the operation

  • 5 Create Single Geometry - input to specify whether the splitted STL faces should be put into a single geometry or each should be placed in a separate geometry

  • 6 To approve the operation click Split

Extract Features

extract features

Extract Features operation will generate edges for an STL where the angle between two triangles is smaller than Maximum Feature Angle . The edges will be generated, loaded and displayed in the graphics window. These edges will be later used by the meshing algorithm to accurately resolve sharp features of the geometry.

To Extract Features:

  • 1 Expand the list of options next to the item

  • 2 Select Extract Features

When you apply Extract Features operation to a geometry a Extract Features panel will appear.

extract features options

Following options are allowed:

  • 3 Maximum Feature Angle - define the limit angle between surface normals below which the edges are marked for extraction. Characteristic values of the parameter:

    • 0 degrees - no edges selected

    • 180 degrees - all edges selected

    • 120 degrees - default angle

  • 4 To approve the operation click Extract

Duplicate

duplicate

Duplicate - copy the geometry and paste as a new one. In that way, new geometry is created identical to the current one. The new component has an automatically generated name - a suffix with a number is added to the original name.

To duplicate the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Duplicate

  • 3 New geometry will appear in the geometries list

Replace

replace

Replace - option for replacing current geometry with another one. Option is available only for imported geometry. The current geometry will be removed and a new geometry will be imported instead of an old one.

To replace the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Replace

  • 3 Point to the new geometry and press OK

Delete

delete

Delete - removes the selected geometry from the simulation.

To delete the geometry:

  • 1 Expand the list of options next to the item

  • 2 Select Delete

When apply to Delete operation to a geometry, it is not immediately removed but is put into delete queue. Current state of the delete queue is displayed at the bottom of the panel.

img 595417c6d451d

Any geometry in the delete queue can be restored by clicking on a respective button. However, every time you leave the Geometry panel the queue is cleaned and the geometries are deleted permanently.

Multiple Geometries Deleting

delete multiple geometries

To delete multiple geometries at once:

  • 1 Select the items from the geometries list

  • 2 Click the Delete button at the top bar

Boolean Operations

boolean

Boolean operations are used for combining geometries in various ways to create new more complex geometric forms. Boolean operations are available for solid, shell and primitives geometry except the STL format geometry. While selecting two or more geometries from the list, boolean operations buttons will be displayed on a title bar. Currently, the following operations are available:

  • 1 Unite - items are combined into a single geometry. The union of two geometries A and B is the region in geometry A, B or in both A and B. The union operation is commutative and order of selection does not matter.

unite
  • 2 Intersect - the result is the common part of the geometry. The intersection of two geometries A and B is the region inside volume A that is also inside volume B. The intersection operation is commutative and order of selection does not matter.

intersect
  • 3 Subtract - all other objects are subtracted from the first object. The difference of two geometries A and B is the part of the geometry A volume that is not belonging to B. Order of selection matters for boolean subtract.

subtract

Geometry Properties

properties

Properties - describe the features that allow you to edit the geometry in SimFlow. For the geometry created in SimFlow, it is possible to change its dimension and origin. For the imported geometry, it allows you to edit import parameters. Properties option is not available for STL items.

To find this option:

  • 1 Place pointer over a row in geometry list and click Properties icon

Edit Primitives Geometry

properties primitives

Properties button activates geometry edit mode which shows geometry properties panel. It also changes geometry view in the 3D window enable editing. Note that, currently you will be able to edit properties of primitive geometries and this options will not be available for geometries imported from external files.

Edit Imported Geometry

properties imported

Properties of imported geometry refers to the Surface Quality level. Due to the mesh input geometry is always STL format, all others geometries should be converted to the STL. Surface Quality determines by the density of surface division into triangles. It has an impact on the quality of meshed surface, however to high level of surface quality significantly extends the meshing process.

Three level of quality are available in order of accuracy:

  • Normal

  • Fine

  • Very Fine

It is good practice to gradually increase the quality level to achieve a satisfactory surface quality at a low numerical cost.

Face Groups

geometry faces

Face Group is the set of surfaces belonging to one geometry separate from other faces to assign different properties. It is usually used to assign boundary condition or set a special mesh attributes.

Geometry Faces button is visible when the pointer is placed over a row in geometry list. It activates face edit mode which shows Face Groups panel and switches 3D geometry selection mode to allow face selection.

Create Face Group

geometry faces options

All geometry faces are initially put into the default group. To extract the group of faces for example to define different boundary condition, separate face group need to be defined. In Geometry Faces panel the following options are available:

  • 1 List of current face groups. Face Group can be renamed by double-clicking on the name. However, the default group cannot be renamed.

  • 2 Extract Group (available only for STL geometries) button allows to extract face group into a separate STL geometry

  • 3 Clear Selection button allows to clear group list and graphic face selection

  • 4 Create New Face Group button allows to add new face groups to the list using one of two options:

    • 5 Create Empty Group allows to create an empty group and add faces to it later

    • 6 Create Group From 3D Selection allows to select some faces in the graphics window and put them into a newly created group

Editing Face Group

img 595411a2ec61d

It is possible to edit non-default face group after it is selected in the Face Groups list. When a face group is selected all its faces are highlighted in the graphics window. When a face group is selected only Delete button is visible. Any changes to the face selection in graphics window will cause two additional edit buttons to appear:

  • 1 Update Face Group button will cause the content of the currently selected group to be equal to the selected faces in the graphic window

  • 2 Reset Face Group button will reset graphic window face selection to be equal to the group content

  • 3 Delete button will remove an existing face group. If the removed group contained some faces they will be moved into the default group.