Documentation

Tutorial: Hex-dominant parametric – Mesh around a vehicle

This short tutorial shows how to create a mesh using the automated Hex-dominant operation for internal flow analysis.

Link to tutorial project containing the geometry:

Import tutorial project into workbench

  • As a first step we need to create a new simulation. To create a simulation left click on external flow simulation and then on Create Simulation.
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Ahmed Body for external flow simulation
  • This dialog box allows the user to select the simulation model. Click on ‘Incompressible’. 

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    Incompressible flow analysis for external flow simulation
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Incompressible flow settings for external flow simulation

The default settings for the simulation are kept the same. Save the simulation model by clicking on the tick mark.

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.
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Bounding Box Resolution in mesh settings
  • Scroll down to specify the Number of computing cores for the meshing operation (16 in this tutorial)
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Selecting the number of processors for meshing

BACKGROUND MESH BOX

  • An important parameter is the size of the base box, which is used as the surrounding fluid domain.
  • To change the size of the box click on Background Mesh Box expand geometry primitives under Mesh and change the coordinates of Background mesh Box as shown below

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    Background mesh Box coordinates for external flow simulation

Material Point

  • 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 base mesh box but outside the body.

Select the Material Point and give the coordinates as below:

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    Material Point Coordinates for external flow simulation

Feature Refinement

  • In order to resolve the features of the vehicle accurately you can add a Feature Refinement under the Mesh Refinements.
  • Click on Refinements and add an feature refinement and keep the default values as mentioned below.

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    Feature refinement settings for meshing

Surface Refinement

  • 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
  • We keep the Minimum and Maximum Refinement levels at 2 and we select the entire volume by using volume select icon

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    Surface refinement settings for external flow

Boundary Layer Refinement

  • Select the  Inflate Boundary layer setting
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Boundary layer refinement settings
  • keep the default settings in the dialog box
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Boundary Layer Refinement settings
  • The next step is to pick the faces.
  • All faces except the inlet and outlet faces need to be selected.
  • Select all the faces of the pipe by dragging the Active box selection over the pipe and deselect the inlet and outlet faces by clicking on them.

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    Boundary Layer faces selection

Mesh Inspection

  • After the mesh generation we need to select the mesh as our domain of simulation.
  • Click on generate mesh clip to inspect the internal mesh. Adjust the settings of the normal. Click on generate mesh clip icon.

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    Mesh inspection showing mesh refinement regions
  • The boundary layer is clearly visible on zooming
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Boundary layers on the mesh
  • Hide all the bounding faces to view the surface refinement on our body

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    Surface refinement seen on the mesh after hiding the bounding faces
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