Documentation

Tutorial: Turbulent incompressible flow in a cyclone separator

In this tutorial, a fluid dynamics analysis of a cyclone separator is presented. The flow through the separator is modeled as a incompressible, turbulent flow using a k-epsilon turbulence model.

Tutorial Link:

Import tutorial case into workbench

Step-by-step

Import tutorial project

  • To start this tutorial, import the tutorial project into ‘Dashboard’ via the link above.
  • Once the ‘Work bench’ is open you will be in the ‘Geometries’ tab.
  • Click on the CAD model named “Cyclon” to load the CAD model in the viewer
  •  The CAD model is displayed in the viewer like shown in the figure below
  • You can interact with the CAD model as in a normal desktop application
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CAD model

Create a New Simulation

  • To create a new simulation click on the ‘+’ option next to the ‘Simulations’ tab
  • Select the ‘Incompressible Flow Analysis type and click ‘Ok’
  • After clicking ‘Ok’, a new tree will be automatically generated in the left panel with all the parameters and settings that are necessary to completely specify such an analysis.
  • All tree items that are completed are highlighted with a green check. Items that need to be specified have a red circle. While, the blue circle indicates an optional settings that does not need to be filled out
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Creating a new simulation
  • k-epsilon is used for turbulence modelling
  • The Steady-State analysis option is activated

Creating the mesh

  • Select the mesh option and set the parameters as shown in figure below
  • We use the automatic ‘Hex-dominant (only CFD)’ algorithm and set the fineness to ‘Fine’
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Mesh parameters
  • Next  is to add “Mesh Refinements”.
  • To add a refinement click on the ‘+’ next to the Refinements and select the required refinement from the drop down menu
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Adding mesh refinements
  • Firstly, select the ‘Inflate Boundary Layer’ option from the drop down menu
  • To specify where the refined boundary layer shall be generated, we first need to select all the physical walls of the CAD model
  • Since there are many, use the ‘invert selection’ option
  • Therefore choose all inlet and outlet faces (3 in total) of the model which are NOT physical walls ( 1 inlet and 2 outlets, top and bottom )
  • Then click the ‘Invert selection’ option (by right click), as shown below
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Using the Invert selection
  • Assign these faces for the mesh refinements as shown below and save the operation (hit the blue tick button)
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Inflate Boundary layer- Refinement
  • Go back to the ‘Mesh’ option and hit the Generate button to start the mesh operation
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Starting the mesh operation
  • After some time, the mesh generation will be finished and it can be reviewed via the 3D viewer
  • The resulting mesh is shown below
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Resulting Mesh

Adding materials to the domain

  • Next, add the materials from the ‘Material Library’ . First, we start with clicking on sub-tree “Materials”, click on ‘+’ from the options panel as shown.
  • This pops-up a ‘Material Library’ from which we select “Air” and click on ‘Ok’. This will then load the standard properties for Air.
  • Then, assign the material to the domain and save.
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Adding materials
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Assigning material to the domain

Initial Conditions

  • Next item is Initial conditions. Here you can specify the state of the fluid at the beginning of the simulation. The following initial values are used:
Variable Value Unit
pressure 0 m^2/s^2
velocity (x, y, z) (0, 0, 0) m/s
k 0.08 m^2/s^2
epsilon 0.036 m^2/s^3

Boundary Conditions

Next, define the boundary conditions.

  • To create a boundary condition, click on the ‘+’ option next to the Boundary conditions and select the required boundary condition from drop down menu, as shown in figure.
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Creating a new boundary condition
  • For the Inlet select the ‘Velocity Inlet’ boundary condition, specify the values shown in the figure below, assign inlet face for this boundary condition and click on save.
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Velocity Inlet Boundary condition
  • For the outlet add a pressure outlet boundary condition and specify the settings as shown in figure below, assign the outlet faces (top and bottom faces), as shown in figure, for this boundary condition and save it.
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Pressure Outlet Boundary Condition
  • Similarly, add a No-slip ‘Wall’ boundary for the remaining faces
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Wall Boundary Condition

Numerics

  • The next item is Numerics. Here one can specify the numerical setup of the simulation.
  • We use the default Numerics as shown below
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Numerics

Simulation Control

  • Under Simulation control we can specify the global parameters of the simulation run
  • Since we are running a steady-state analysis, the time steps are only “quasi time steps”
  • Set the parameters as shown in figure below.
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Simulation Control

Start a simulation run

  • The last thing to do for running this simulation is to create a run.
  • The new run is created by clicking on the ‘+’ symbol next to ‘Simulation Runs’
  • Give a name to the run and start the run
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Creating a new run

Post-Processing

  • Once the simulation run is finished, the results can either be post-processed in the integrated post-processing environment
  • Or they can be downloaded and post-processed locally (e.g. with ParaView)

Use the integrated post-processing system for result analysis as follows:

  • Select the ‘Solution fields’ under the Run to post process the results
  • Click the ‘+’ next to the ‘Cutting Planes’ to create a new cutting plane
  • Vary the position of the Cutting Plane using the ‘Point’ option (highlighted)
  • Set the scalar to ‘All velocity [node]’ to view the velocity distribution at the cross section of the cyclone separator
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Velocity Contours at a cross section of the separator

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