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Tutorial: Thermal Analysis of a Differential Casing

This article provides a step-by-step tutorial for the thermal analysis of a front differential casing. The objective of this simulation is to analyze the temperature distribution across the casing in operation mode.

temperature field differential casing thermal simulation
Figure 1: The temperature field of the differential casing.

This tutorial teaches how to:

  • Setup and run a thermal simulation.
  • Assign boundary conditions, material, and other models to the simulation.
  • Mesh the geometry with the SimScale standard meshing algorithm.
  • Explore the results using SimScale online post-processor.

The typical SimScale workflow will be followed:

  1. Prepare the CAD model for the simulation.
  2. Setup the simulation.
  3. Setup the mesh.
  4. Run the simulation.
  5. Analyze the results.

1. Prepare the CAD Model and Select Analysis Type

To start, you can import a copy of the project into your workbench to follow along the steps by clicking the button below:

The following picture shows what should be visible after importing the tutorial project. You can find the geometry ‘Differential_Casing’ and the 3D model displayed. You can interact with the model as with any CAD program.

CAD model differential casing thermal simulation
Figure 2: CAD model displayed in the viewer.

1.1 Create the Topological Entity Set

Especially interesting for our simulation is the creation of Topological Entity Sets, which basically means that we can group faces together for later boundary condition assignment. To start, select the geometry element in the tree at the left panel.

The Topological Entity Sets can be found at the right panel:

topological entity sets differential casing thermal simulation
Figure 3: Topological Entity Sets.

A number of entity sets is already provided in the initial project, but one set for the ‘Heated Region 2’ boundary condition is still missing. The picture below shows how to create it:

creating topological entity set differential casing thermal simulation
Figure 4: Select the faces for the topological entity set.
  1. Select the corresponding set of faces as shown.
  2. Click the ‘+’ icon at the right of Topological Entity Sets in the right panel.

In the pop-up dialog that appears, name the set ‘Heated Region 2’ and click the blue Create new set button.

creating topological entity set differential casing thermal simulation
Figure 5: Naming and creating the topological entity set.

1.2 Create a Heat Transfer Simulation

Now the simulation setup can be started. Follow these steps to create a new simulation:

create simulation differential casing thermal simulation
Figure 6: Create new simulation.
  1. Select the ‘Differential_Casing‘ geometry element at the left panel.
  2. Click the blue Create Simulation button in the pop-up window.

The simulation library window appears. Select the ‘Heat Transfer‘ analysis type and click the blue Create Simulation button as shown in the picture:

simulation library differential casing thermal simulation
Figure 7: SimScale simulation library.

Now 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 parts that are completed are highlighted with a green check. Parts 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.

You can read more details about the heat transfer simulation type in our documentation page:

And the SimWiki page:

2. Setup the Simulation

2.1 Material Model

Next, add the material model from the ‘Material Library’. First, we start with clicking the ‘+’ button next to the ‘Materials’ tree element at the left panel. This pops-up a ‘Material Library’ from which we select ‘Aluminium‘ and click on the blue Apply button. This will then load the standard properties for Aluminium.

materials library differential casing thermal simulation
Figure 8: SimScale materials library.

In the pop-up material properties window, our only body is automatically selected. Accept the selection with the blue check-mark button.

Figure 9: Assigning a material to the domain.

2.2 Boundary Conditions

Now, we come to define the boundary conditions. To create a boundary condition, click on the ‘+’ button option next to the ‘Boundary conditions‘ element at the left panel, and select the required boundary condition type from drop down menu, as shown in figure.

creating boundary condition differential casing thermal simulation
Figure 10: Creating a boundary condition.

We can see that we can define either temperature or heatflux boundary conditions. For our simulation, we’ll only need heatflux boundary conditions, since we will assign a specific heat load inside the casing and a convection condition at the outside.

A. Heated Region 1

We will start with the first inner heat loss boundary condition for the face set Heated Region 1. Select the Surface heat flux boundary condition from the boundary conditions drop-down menu. Give a heat flux value of 2900 W/m^2, since this comes close to the thermal conditions we want to test in this simulation. Assign this to the Heated Region 1 entity set. Give an appropriate name to the boundary condition, such as ‘Heated region 1’.

heat flux boundary condition differential casing thermal simulation
Figure 11: Heated region 1 boundary condition.

B. Heated Region 2

The second boundary condition is also a heat flux boundary condition of type Surface heat flux with a value of 3600 W/m^2 assigned to face set Heated Region 2.

heat flux boundary condition differential casing thermal simulation
Figure 12: Heated region 2 boundary condition.

C. Outside Faces

The third boundary condition is a heat flux boundary condition of type Convective heat flux with a reference temperature of 19.85°C, and an h value of 24 W/m^2 K assigned to the face set Outside. The value for the outside heat transfer coefficient for the convection boundary condition is taken from literature and is rather a rough assumption, since this coefficient won’t be constant over the whole surface in reality.

convective boundary condition differential casing thermal simulation
Figure 13: Outside boundary condition.

These three boundary conditions are sufficient to simulate the thermal scenario we are interested in: Heat loss from the inside, and natural convection at the outside faces of the casing.

3. Mesh Setup

Select the mesh option and keep the default settings as shown in the figure below. You do not need to click the Generate button at this step, as the mesh will be computed as part of the simulation run.

mesh setup differential casing thermal simulation
Figure 14: Mesh setup.

Note that the results generated with first order elements might not be as accurate as with second order elements, but choosing a second order mesh will lead to longer computing times, so it is avoided in this case.

As for the fineness of the mesh, a Fineness level of 5 is enough. As a rule of thumb, one should make sure that the resulting mesh does have more than one volume layer across the cross-section of the model.

4. Start the Simulation

The last thing to do for running this simulation is to create a run. The new run is created by clicking on the ‘+’ button next to ‘Simulation Runs’:

In the pop-up window, you can give a meaningful name to the run, then click the blue Start button to start the run.

create new run differential casing thermal simulation
Figure 15: New simulation run.

The Job status box in the lower left again provides updates about the job status. Also, a Solver log is provided after a few seconds which shows the exact output of the actual computing algorithm. The simulation run should take a few minutes to be carried out. Once the simulation run is Finished we can Postprocess the results.

5. Post-Processing

Once the simulation is finished, select the ‘Solution fields’ under the Run to post-process the differential casing analysis results on the platform:

post-processing temperature profile plot thermal simulation
FIgure 16: Temperature profile on the differential casing.

In this plot image, the blue color corresponds to the colder regions, and red corresponds to hotter. The minimum temperature is found to be 337.9 K and the maximum is 341.1 K.

If you want to learn more on SimScale’s online posprocessor, you can have a look at our post-processing guide:

Congratulations, you finished the differential casing tutorial!

Note

If you have questions or suggestions, please reach out either via the forum or contact us directly.

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