Run a conjugate heat transfer simulation¶

Conjugate heat transfer (CHT) solves energy and momentum together, so it captures buoyancy and natural convection as well as forced convection. In Bramble, CHT is a steady solve of the fluid regions only.

Set up the Template Case¶

1. Copy or open a Template Case. In the editor's header card, click Edit. In Update Template Case:

   • set Methodology group to OpenFoam with CHT
   • add the CHT workflows to Workflows, for example Foam CHT 1806F RANS

   Click Update. If the editor then shows Template Case was automatically updated, click Save to keep the added data.

2. On the Solutions tab, in Solution Stage, Solution is fixed to Steady State (CHT). Fill in the iteration counts for each stage:

   • Limited Incomp Iterations
   • Incomp Iterations
   • Comp Iterations
3. On the Domain tab:
   • In Ref Params, set Temperature (K), the reference air temperature.
   • To hold the ground near the car at the reference temperature, turn on Fixed Ground Temperature with Toggle On.
4. On the Other BCs tab, in Temperature, click New for each set of hot or cold surfaces:
   • Component and Regex: the zones the temperature applies to.
   • type: Simple for one temperature in K, or Ramp for a table of Time (s) and Temperature (K) pairs. Without a type, the row shows "Select the type of the temperature".
   • Tags: optional.
5. On the Forces tab, in Solve Heats, add a row for each group of surfaces whose heat you want reported: a Name and a Regex that matches the zones.
6. Set up radiators, rotating wheels and the rest of the Template Case as for any OpenFOAM case. See radiators and porous media and rotating wheels.
7. Click Save in the header.

Set up and launch the Run¶

1. On the Run's CFD Setup tab, click the edit icon next to an Attitude's name.

2. In CFD Attitude Setup, choose the CHT Methodology and Workflow, and your CHT Template Case.

3. Click Save, or Save to All.

4. Launch the Run.

Fast restart doesn't work with CHT methodologies: the Mapped Solution Donor Case pickers are disabled.

Results¶

• Surface and movie exports can include the thermal variables T (temperature), htc (heat transfer coefficient), qConv and qCond. Add them to the Fields of your surface-group and movie exports on the Exports tab.
• Bramble collects the heat through each Solve Heats group, and temperatures, from the solve.

To have CHT variables included in your Account's standard postpro, contact support@bramblecfd.com.

Scalar transport or CHT?¶

Some Accounts also have thermal workflows that use scalar transport. Both predict temperatures, but they model different physics.

For a comparison study, see Scalar vs. conjugate heat transfer modelling on the Bramble website.

Related: Template Case editor reference · Methodology, workflow and Template Case · Export results