3D Mixer with Pitched-Blade Turbine Impeller Using OpenCascade Sharp-Immersed Boundary#

The mixing of stirred tanks is a common chemical engineering problem that can be tackled through immersed boundary simulation. This example, a variation of 3D Mixer with Pitched-Blade Turbine Impeller Using Composite Sharp-Immersed Boundary, illustrates how the transient flow in a stirred-tank can be simulated by Lethe using the Sharp-Immersed Boundary formulation with an OpenCasacade shape from a .step file.

Features#

  • Solvers: lethe-fluid-sharp

  • Transient problem

  • Rotating complex solid, defined by a .step file using the OpenCascade shape, modeled with sharp immersed boundary

Files Used in this Example#

Both files mentioned below are located in the example’s folder (examples/sharp-immersed-boundary/3d-opencascade-mixer-with-pbt-impeller).

  • Parameter file: mixer.prm

  • .step file: impeller.step

Description of the Case#

In this example, we simulate a mixer using a PBT impeller through the usage of a .step file with the OpenCascade shape feature of the sharp immersed boundary solver.

Creation of the STEP File#

The .step file can be defined using any CAD tool available to the user. The .step file must represent a solid. It is preferable to avoid .step files that represent shells, composite of solids or a compound of objects.

Tip

Use the union tool at your disposal to avoid issues with .step files that are defined by a composite of solids. Most CAD software offers the possibility to define a solid from the union of multiple solids. Similarly, if the .step file is only defined by a shell, it is usually possible to define a solid from that shell. If your CAD tool does not allow these operations, the FreeCAD software allows you to do these operations using the part toolbox.

Parameter File#

Definition of the Shape and Its Motion#

The section defining the solid is almost the same as in 3D Mixer with Pitched-Blade Turbine Impeller Using Composite Sharp-Immersed Boundary, with the difference being the shape type and shape arguments.

subsection particles
  ...
  subsection particle info 0
    ...
    set type            = opencascade
    set shape arguments = impeller.step
  end
end

Additional information on the particles parameters can be found on Sharp-Immersed-Boundary.

Results#

The velocity field obtained with this example is similar to the one obtained with the Nitsche immersed boundary and with the shape defined as a composite.

Velocity field norm

Using meter and second as the length and time unit and assuming a fluid density of \(1000 \left(\frac{\text{kg}}{\text{m}^3}\right)\) produce the following torque on impeller:

Impeller Torque