Tutorial: Hex-dominant parametric – Valve Geometry
In this tutorial, the meshing process for a valve geometry is carried out using the “Hex-dominant parametric” approach.
The “Hex-dominant parametric” is the semi-automatic meshing option that uses hexahedral cells and allows full flexibility in meshing parameters with all type of refinements options.
Import tutorial project into workbench
As a first step we need to create a new simulation. To create a simulation left click under the Geometries and then on
Create simulation for the pipe geometry
Note: the STL geometry is pre-split to separate the faces for meshing and later assignment of boundary conditions.
The Valve cane seen by hiding all the faces except face-3
Image showing the valve inside the pipe after hiding all the faces
Select the simulation model. Click on
. Incompressible Analysis for pipe internal flow keep the default settings of the simulation the same.
keep the default settings for the incompressible flow simulation Mesh Generation
Left click on the
mesh icon to create a new mesh. Choose the
Hex-Dominant parametric (only CFD) Algorithm. Select the number of cells in each direction for Bounding Box as shown in the figure below.
Bounding box resolution settings for the mesh Scroll down to specify the
Number of computing cores for the meshing operation (16 in this tutorial)
Specify the number of processors for meshing Back Ground Mesh Box
An important parameter is the size of the base box, which serves as the bounding coordinates for the mesh.
To change the size of the box click on
Back Ground Mesh Box expand geometry primitives under Mesh and change the coordinates of Base mesh Box as shown below
Set up the coordinates of the back ground mesh box
Material point: This is the parameter the algorithm uses to determine wether the mesh is created inside a shape or outside. In this case this point therefore lies within the geometry.
Material Point and give the coordinates as below:
Set up the coordinates of the material point coordinates
Now we create additional
Geometry Primitives, to be used later for region refinements. Click
Geometry primitives and ‘add new primitive’ of type Cylinder as shown in figures below.
Setting up geometry primitives Specify the name ‘Cylinder-Valve’ and following values, then save to get the shown cylinder region.
Set up the coordinates of the geometry primitive Similarly create 4 more primitives of ‘Type: Cylinder’ as detailed in the table below:
These will be later used to refine the up/down stream regions, the opening gap between the valve and pipe, and hinge areas.
Details of the geometry primitives to be setup The figure below illustrates the created primitives:
All the geometry primitives created can be seen here Mesh Refinement
Here we will add the necessary refinements for the surfaces, edges and regions to generate a fine mesh of optimum size.
The refinement levels given are relative to the ‘baseMesh’ cell size with each level reducing the size to half.
see Hex-dominant parametric documentation for details.
In order to have a finer mesh over the surface of the body, we add surface refinement.
Click on Refinements to add a new refinement and select
surface refinement . Re-name it to ‘Surf-pipe-inlet-outlet’ and select a Type ‘Surface refinement’ to specify the parameters as shown in figure below.
This will refine the pipe, inlet and outlet surfaces. Select the shown faces and click save.
Select the minimum and maximum level surface refinement as 2 and 3 respectively
Surface refinement settings and face selection
Create 1 more surface refinements for the valve surface as detailed in the figure below:
Surface refinement settings for valve surfaces Feature Refinement
This refinement is important to resolve the feature edges of the geometry and produce a fine mesh at the edges.
Add a new mesh refinement and select type ‘Feature refinement’ for refinement near edges. Re-name and enter the values as detailed in the figure below.
This will now apply a level-5 refinement at a distance of 0.01m from the extracted edges in all directions.
Feature refinement settings for our simulation Region Refinement
Region refinements will refine the volume mesh cells based on the given refinement level. These are important to get a fine volume mesh in the vicinity, upstream and downstream of the valve.
Now we add ‘Region refinements’ using the geometry primitives created before to refine the volume mesh.
So add a new mesh refinement, rename to ‘Reg-hinge-1’, select Type ‘Region refinement’ and specify the settings as shown below and save.
This will apply a level 7 refinement inside the selected region.
Region refinement settings for our simulation Similarly, create 3 more ‘Region refinements’ as detailed in the table below:
Table for region refinement settings Layer Refinement
Lastly, add a ‘Layer refinement’ for resolving the viscous region of the boundary layer. Specify the settings as shown below.
This will generate 3 layers based on relative size.
Choose the inside physical walls and valve i.e the face_3 and face_4 from the assignment box and click save.
boundary layer refinement settings and face selection Advanced Settings
To generate a mesh of optimum quality, make sure the advance settings are set as shown in the figures below.
For ‘Castellated mesh’ and ‘Span’ controls:
Castellated mesh and Span control settings for the mesh
Layer adding controls for the mesh
For ‘Mesh Quality control’:
Mesh quality control settings Mesh Inspection
After the mesh is generated, use the mesh as the domain for simulation and click on reset the assignments when prompted.
The generated mesh with the mesh refinements is presented below:
Mesh showing region refinement and surface refinement The Mesh generated on the valve can be seen by hiding the other faces.
surface refinement can be seen by hiding all the faces