Docs

Thermal analysis: Differential casing

Note

The content of this tutorial is not up to date with the current live version of SimScale. The tutorial setup and the results are still valid! Please do not get confused if styles like buttons and entity names have changed in the meantime.

In this tutorial the thermal behavior of a front differential casing is simulated. The objective of this simulation is to analyze how hot the casing will get in operation mode as well as if there are any hot spots visible that could be avoided with a more suitable casing design.

The temperature field of the differential casing.

The temperature field of the differential casing.

Import tutorial project into workspace

Step-by-step

1) Getting started

  • To start this tutorial, you have to import the tutorial project “Tutorial-03: Differential casing thermal analysis” into your ‘Dashboard’ via the link above.
  • Alternatively, you can also add the tutorial project from the ‘Public Projects’ library by searching for ‘tutorial’.
Search on community

‘tutorial’ search on community

  • Clicking on the project, then clicking on ‘Actions’ and ‘make a copy’ option to add it to your ‘Dashboard’. This process is illustrated by the figures below.
Make a copy through Actions

Making a copy of project to add it to Dashboard

  • Once the project is in your ‘Dashboard’, simply move the mouse over to the upper right corner click on the blue icon to open it in your workbench as shown in figure below.
Opening project from dashboard to workbench

Opening project from dashboard to workbench

2) Mesh Generation

  • Once the ‘Work bench’ is open you will be in the ‘Mesh creator’ tab.
  • Click on the CAD model CAD-differential-casing_v1 to load the CAD model in the viewer
The CAD model displayed in the web browser

The CAD model displayed in the web browser

  • To create a new mesh from this CAD model, click the blue Mesh geometry button
  • Automatically, a new mesh called CAD-differential-casing_v1 mesh is created and a default mesh operation called Operation 1 (you may rename it to a useful name)
  • To specify how exactly the mesh shall be generated, click on the operation itself i.e. Operation 1
  • Let’s first give it a meaningful name - e.g. automatic-tet since we will use an automated tetrahedral mesh operation to generate the mesh
  • First we need to choose the meshing type which basically defines the algorithm that will be used to create the mesh
  • For this thermal analysis, we will use the Fully automatic tetrahedralization mesh operation
  • It only has a few settings to choose: We set Mesh order to First order, the Fineness to 2 - Coarse and Number of processors to 4
Choose the type of mesh operation and its settings

Choose the type of mesh operation and its settings

  • That’s all there is to define the mesh operation. Let’s start it by clicking the Start button on the top of the page
  • Confirm the dialog to start the operation
Confirm that you want to start this mesh operation

Confirm that you want to start this mesh operation

  • The Job Status box in the lower left will show the progress of the operation
  • Queued means that the SimScale platform is preparing a computer to carry out the operation
  • Computing means that the mesh operation is currently carried out
  • After the first seconds of computing, there will appear a Meshing Log tree item below our mesh operation in the tree
  • This is the direct command line output of the meshing framework, that in the beginning might be a bit cryptic but can be very useful if a meshing operation fails
The meshing log providing details of the mesh operation execution.

The meshing log providing details of the mesh operation execution.

  • Once the mesh operation is finished, the Job status box will show the green Finished box
  • The mesh immediately appears in the viewer and we can see the small elements that have been created
  • The advantage of running the mesh operation remotely is that you do not have to wait until the mesh is finished. You can simply move on and already work on the simulation setup since your local computer is not used at all for computing
The completed, tetrahedral, first order mesh.

The completed, tetrahedral, first order mesh.

  • This was all it takes to create an automatic, tetrahedral mesh on SimScale. You can also see the created elements of the mesh from inside at some cutout. To do so, apply a Mesh Clip filter by clicking on the Filter dropdown menu on top right and selecting Mesh Clip.
  • Next you will see a cutting plane which you can adjust under Mesh Clip parameters. For example, in this case give Normal (y) a value of -1 in order to clip the mesh from the middle of the geometry. Click Preview button to see the cutting plane. The black arrow shows the direction of clipping. Figure below elaborate the steps.
The mesh clip mechanism

The mesh clip mechanism

  • Click the Apply button to see the clipped mesh. Figure below shows the clipped mesh.
The inside of the volume mesh.

The inside of the volume mesh.

  • To get back to the standard mesh view, choose Filter and click on Clear Filter
  • Now let’s move on to the actual simulation setup.

3) Simulation Setup

Now after we have created the mesh, let’s define the actual simulation.

  • First switch to the Simulation Designer tab next to the Mesh Creator tab
  • Click on New Simulation
  • Give it a meaningful name
Give the simulation a meaningful name.

Give the simulation a meaningful name.

  • The first thing to do in any simulation setup on SimScale is to choose the actual analysis type that we want to carry out.
  • In our case, we are interested in running a thermal simulation in a solid body, so we choose Thermostructural analysis and then Heat transfer
  • At the bottom of the Analysis Type panel, we can see the detailed settings of the analysis type
  • For this tutorial, we will choose a Steady-state simulation which means that we neglect transient effects and are only looking at the final equilibrium state of the system
Choose the analysis type and its detailed settings.

Choose the analysis type and its detailed settings.

  • To confirm this analysis type hit the blue Save button
  • Immediately the analysis template is loaded and the tree on the left is expanded
  • We can see different icons, that indicate different tasks
  • The red circle indicates that this item is missing something - a definition, or a choice
  • The green check means that this item is already completed - however you might want to check on the default values since they might not make sense for your simulation
  • The blue circle indicates an optional settings that does not need to be filled out
  • Now we simply work our way from top to bottom of the simulation tree to complete the simulation setup
The simulation designer tree with all items necessary to complete the simulation setup.

The simulation designer tree with all items necessary to complete the simulation setup.

  • The first item is the Domain which defines the actual model or mesh on which you want to run this simulation
  • We choose the mesh we just created called CAD-differential-casing_v1 mesh and hit the blue Save button
  • Immediately, the chosen mesh is loaded in the viewer
The mesh that has been assigned to our simulation.

The mesh that has been assigned to our simulation.

  • The Domain tree item is then expanded with the items Geometry Primitives, Topological Entity Sets and Mesh
  • 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
  • So click on Topological Entity Sets
  • We create the first Topological Entity Set by selecting the first heated region at the inside of the casing (see image below)
Selecting the heated region 1 via the viewer.

Selecting the heated region 1 via the viewer.

  • Then we hit the blue Create entity set from viewer selection
Choose a name for the entity set.

Choose a name for the entity set.

  • After we confirmed the name of the topological entity set, the new set appears in the table
  • See below how the other face sets are defined. The idea is that internally, there are two different heat losses and externally we will assign natural convection as a cooling mechanism
  • We repeat this process until we have all of the topological entity sets defined:
Set name Purpose
heated-region-1 Internal heat loss 1
heated-region-2 Internal heat loss 2
outside Natural convection outside
The selection for the 'heated-region-2' face set.

The selection for the ‘heated-region-2’ face set.

The selection for the 'outside' face set.

The selection for the ‘outside’ face set.

  • The next relevant tree item is Material where we click on the blue Add Material button to add a new material
  • The standard material Steel and its properties is added
  • As our casing is made out of aluminum, we hit the Import from material library button, choose Aluminum and click the blue Import button
  • To complete the material setup, the only thing that is left to actually assign this material to one of the volumes of our mesh. Since it only has one, we simply have to check the volumeOnGeoVolumes_0 in the table
Aluminum as material defined and assigned to the existing volume.

Aluminum as material defined and assigned to the existing volume.

  • The next tree item Initial conditions allows to define the initial temperature within the casing
  • The green check indicates that default values have already been chosen for it, which we will leave unchanged and move on to Boundary conditions
The boundary condition dialogue.

The boundary condition dialogue.

  • 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 loss inside the casing and a convection condition at the outside
  • Depending on the analysis type we chose, there would be even more boundary conditions available
  • We will start with the first inner heat loss boundary condition for the face set heated-region-1
  • So we click on the blue button Add heatflux boundary condition
First heatflux boundary condition.

The first heatflux boundary condition

  • Automatically, a new boundary condition called ‘boundary condition 1’ is created
  • First we’ll give it the meaningful name q-region-1 which indicates that it is a heatflux (q) boundary condition for the heated-region-1 face set
  • Next we’ll choose the type Surface heat flux since we want to define the heat loss generated inside of the casing as a surface heat flux across all faces of heated-region-1
  • Next we actually define the value. We chose 2900 W/m^2 since this comes close to the thermal conditions we want to test in this simulation
  • To complete the boundary condition setup, we have to choose on which faces this boundary condition shall be assigned to, and here the face sets defined earlier do help us
  • The table already shows the 3 sets we created. So we simply check the heated-region-1 face set and our boundary condition is fully defined
First heatflux boundary condition completely defined.

The first heatflux condition completely defined.

  • To check if we have assigned the BC to the correct faces, we can use the blue Select assignment button at the bottom of the boundary condition settings panel
  • This immediately selects the faces where this BC has been assigned to
Checking where the BC was assigned to via the 'Select assignment' button.

Checking where the BC was assigned to via the ‘Select assignment’ button.

  • Overall we have to define 3 different boundary conditions - 2 for the inside heated region, and one for the outside
  • The setup for each boundary condition is the same: Give it a name, choose a type, choose the values and then assign it to a face set
  • So the second boundary condition is also a heatflux boundary condition of type Surface heat flux with a value of 3600 W/m^2 assigned to face set heated-region-2
  • And the third boundary condition is a heatflux boundary condition of type Convective heat flux with a reference temperature of 293 K, an h value of 24 W/m^2 K assigned to the face set outside
Natural convection boundary condition at the outside of the casing.

Natural convection boundary condition at the outside of the casing.

  • These three boundary conditions are sufficient to simulate the thermal scenario we are interested in: Loss heat coming from the inside and a natural convection at the outside faces of the casing
  • The value for the outside heat transfer coefficient for the convection boundary condition is taken from a book and is rather a rough assumption, since this coefficient won’t be constant over the whole surface in reality
  • The tree item Numerics allows us the control the solving mechanism in detail, where we also won’t change anything in this tutorial
  • The next important tree item is Simulation Control which allows to steer the overall simulation settings
  • We choose a 4 core machine for the computation to have enough computing power for the considerably large mesh
  • We set the maximum runtime to 10,000 seconds to make sure our simulation is not stopped by the system before it is finished
Settings for the simulation control tree item.

Settings for the simulation control tree item.

  • The last step to start this simulation is to create a Simulation Run from it, which basically means that we generate a snapshot of all simulation settings that will be saved and available for later review
  • So we switch to the Simulation Run tree item, and first check the simulation via Check simulation which should be successful, if we haven’t made any mistakes
  • Next, we hit the blue Create new run button and give the run a meaningful name for later review
Creation of a new run.

Creation of a new run.

  • And to start the run, we hit the Start button which will automatically find a machine for the simulation and carry it out
  • The Job status box in the lower left again provides updates about the job status like we saw in the meshing operation
  • Also as we saw in the mesh operation setup, a Solver log is provided after a few seconds which shows the exact output of the actual solver run
  • The simulation run should take a few minutes to be carried out
  • Once the simulation run is Finished we can move on to the Post-processor tab to visualize the simulation results
The completed simulation run.

The completed simulation run.

4) Post-Processing

  • Next we will visualize the results of the simulation we just completed, so we switch to the tab Post-Processor next to the tab we just worked in Simulation Designer
  • We click on the Solution fields tree item on the left under the name of the run we just ran (in my case, it is called 2900-3600-Scenario to indicate which thermal loads I assigned)
  • Immediately after the click, the post-processing environment is loaded with a non-colored view of the results
The initial view of the post-processing environment without a color-coding chosen.

The initial view of the post-processing environment without a color-coding chosen.

  • First, we want to see the temperature field so we click on the Select field dropdown-menu on top of the post-processing window and choose temperature
  • Immediately, the temperature solution field is loaded as a color-coding of the result
The temperature field color map.

The temperature field color map.

  • To toggle the quantitative scale of the color map, we click on the red-crossed button next to the 2900-3600-Scenario text in the post-processing viewer
  • The color scale appears showing which color indicates which temperature
The scale indicating the mapping between temperature values (in Kelvin) and color.

The scale indicating the mapping between temperature values (in Kelvin) and color.

  • Lastly we can also visualize other physical quantities of the results, for example the heatflux across the casing by again switching the field on top of the viewer
Heatflux result field color coding.

Heatflux result field color coding.

  • Congratulations! You just completed a complete thermal simulation using the SimScale platform!