Marine Propeller - CFD Simulation SimFlow Tutorial

In this tutorial, we will be modeling a quarter of the propeller due to the double symmetry condition. You will also learn how to create a Cell Zone (sub-volume in the fluid zone) - this is to mark the location of the rotating zone. Using the MRF model to introduce a pseudo rotation of the propeller - the propeller will be solved in a rotating reference frame and by this, we introduce artificial motion. It is less accurate than resolving motion directly but is more efficient and allows for steady-state simulation of rotating parts. In advanced post-processing using ParaView we show you how to create an iso-surface of a Q criterion.

SimFlow is a general purpose CFD Software

To follow this tutorial, you will need SimFlow free version, you may download it via the following link:
Download SimFlow

Open SimFlow and create a new case named propeller

After creating case Download GeometryPropeller

The STL format does not contain the unit information which are defined during the geometry export. If we do not know the exported unit, we can estimate it based on the total size of the model. It is displayed next to Geometry size label. In our case, the default unit meter is correct.

After importing geometry, it will appear in the 3D window.

We need to create a cylindrical boundary for the domain. For this purpose, we will create a cylindrical geometry for later use in the meshing process.

To better resolve the flow near the propeller, we will create an area with a higher mesh resolution. To do this, we will create a new geometry by copying settings from external geometry.

Radius \({\sf [m]}\)0.3

In order to see all geometries, we will decrease the opacity of the external and refine.

We want to create refinement in the area along the propeller induced flow.

We want to create a mesh of only one blade of the propeller. For this purpose, we will create a base mesh covering only one-fourth of the geometry.

Now we will define material point outside the propeller geometry.

After a few minutes of meshing the following mesh should appear.

After creating the mesh, we have to set proper boundary types.

As we will be simulating only one blade of the propeller we have to create a boundary interface to make the model periodic.

For the simulation of a marine propeller, we will use a steady-state incompressible simpleFoam solver.

For the purpose of this tutorial we will simulate the turbulence phenomenon using \(Realizable \; k{-} \varepsilon\) model.

\(\nu\) \({\sf [m^2/s]}\)1e-06

Note that you do not have to define density. The equations that describe single phase incompressible flow operates on a kinematic pressure(pressure divided by reference density). Therefore, the density property does not explicitly appear and you have to remember to multiply resulting pressure and forces by the density value to obtain a physical results.

To be able to model propeller rotation, we will take advantage of a rotating reference frame. This technique will allow modeling the propeller rotation without a need to rotate the mesh. The rotating reference frame can only be applied to a sub-region of the mesh defined by a cell zone object (a list of mesh cells). Therefore, we will first create a cell zone.

For the purpose of this tutorial we will use the whole mesh as the rotating zone. To do this we need to create the cell zone inside the external geometry.

We will use the same boundary conditions for inlet and external boundaries, to achieve this we can copy settings from the external boundary to inlet.

We want to monitor solution progress by observing force coefficients.

To speed up the calculation process increase the number of CPUs basing on your PC capability. The free version allows you to use only 2 processors in parallel mode. To get the full version, you can use the contact form to Request 30-day Trial

Estimated computation time for 2 processors: 10 minutes

Check if solution converges by observing stabilization of forces on the propeller boundary.

When a simulation is finished, we want to calculate additional solution field to be used in postprocessing.

Please Note: After clicking the Calculate button, SimFlow will calculate the new flow variable, which will be stored in your project folder and will be accessible in the ParaView.

Now we are loading results into the ParaView

To show the propeller we will create now a contour.

As you can see there is only a quarter of the propeller visible and we would like to show the full geometry. In order to do that we have to duplicate and transform a partial propeller.

We have to repeat the previous step to make another transformation - Transorm1 → Transform2

We have to repeat the previous step to make another transformation - Transorm2 → Transform3

To make the full geometry visible, we have to change the visibility of all geometries

In the 3D view the contour of full propeller should appear