Wing - CFD Simulation SimFlow Tutorial

In this tutorial, we are examining the airflow around the wing’s profile. We will focus on the two-dimensional flow around the wing’s airfoil. To enhance precision, we will implement the second-order velocity discretization method following the initial run. The presentation of results will be done in ParaView, utilizing streamlines.

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 wing

Firstly, we need to Download GeometryWing

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.

In order to create the mesh, we need to specify geometry options for the meshing process. We will increase mesh resolution near the wing surface.

Our simulation will be limited to a 2D flow. This can be accomplished by choosing the Plate type as the background mesh.

Material Point tells the meshing algorithm on which side of the geometry the mesh is to be retained. Since we are considering flow around the wing we need to place the material point outside the geometry.

You can specify the point location from the 3D view. Hold the CTRL key and drag the arrows to the destination.

We can define the count of the buffer cells between refinement levels. This parameter determines the width of the transition zone between refined and background mesh. A higher value of this parameter will increase the overall cells count.

After the meshing process is finished the mesh should appear in the graphics window.

For further examination, we should zoom in to see the refinement mesh. Additionally, we can switch projection view from perspective to parallel as the parallel view is more appropriate for visualizing 2D objects.

We want to compute the steady-state solution of the incompressible turbulent flow around the airfoil. For this purpose, we will use the SIMPLE (simpleFoam) solver.

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

The domain has only one external boundary. We will use the Free Stream character type to model the far field conditions. The flow will be aligned with the x-axis.

Additionally, to flow conditions, we will modify default free stream turbulence properties.

In order to measure aerodynamic forces, we will use the force monitor. We will observe drag and lift force coefficients on the aerofoil boundary.

During the simulation, we can observe whether forces on the wing stabilize which will mean that our simulation converges

After the computation is finished we can do a comprehensive visualization of our results with ParaView.

After opening the ParaView, we need to load the simulation results from SimFlow.

We can visualize the flow by displaying the streamlines.

To display the wing geometry with the streamlines, we need to read the geometry file to the ParaView.

Confirm default properties and display geometries with streamlines.

After preliminary calculation, we will continue with a more accurate algorithm. Go back to the Simflow but do not close the ParaView yet. Change velocity discretization to the Linear Upwind scheme. This will decrease numerical diffusion affecting the results.

Estimated computation time: 1 minute

You can observe in the Force Coefficient plot that after switching to second-order the coefficients started to oscillate.

Switch window to ParaView once again. To read newly calculated steps we need to reload the results.

Finally, we can see the results in the 3D window. We observe the flow separation on the second flap. This separation is the cause of the flow instability that we have observed as oscillating values of the force coefficients.