Use donor workflows¶

A donor workflow lets one Attitude, the recipient, reuse the mesh or solution of another Attitude in the same Run, its donor. Bramble starts the recipients automatically once the donor has finished.

Before you start

Your Account needs a Donor Mesh or Donor Solve workflow. Account admins can check the Workflows list on the Account Settings page: donor workflows have "Donor" in their name. If you don't have one, contact support@bramblecfd.com to have it enabled for your Account.
For Donor Solve, you also need a DES Template Case. See run a DES.

Which workflow?¶

Workflow	The recipient reuses	Use it for
Donor Mesh	The donor's mesh. The recipient then runs its own solve	Sweeps where only the flow conditions change, such as speed or yaw, so the mesh is built once
Donor Solve	The donor's mesh and solution. The recipient's DES starts from the donor's RANS velocity and turbulence fields	Running a DES from an existing RANS solve

With a DES donor and a Donor Mesh recipient, only the mesh is reused: the recipient runs its RANS initialisation again.

Workflow names vary between Accounts. Examples are TSFoam RANS 1806C Donor Mesh and TSFoam DES 1806C Donor Solve.

Aeroacoustics uses the same donor rules with a Donor FRPM workflow. See run an aeroacoustic simulation.

Only change conditions that don't alter the mesh

Bramble doesn't compare the donor's and recipient's geometry. Change only boundary conditions, such as velocity or yaw. Don't change the geometry, the mesh recipe, or parameters that move Parts, such as ride heights or steer.

How Bramble pairs donors and recipients¶

Every Attitude whose workflow is a donor workflow is a recipient. Every other Attitude in the Run is a possible donor.
One donor in the Run: every recipient uses it. The names don't matter.
More than one donor in the Run: name each recipient <donor name>__<suffix>, with a double underscore. For example, donor yaw0 and recipient yaw0__DES. The part before __ must match the donor's Attitude name exactly.
The donor and its recipients must use the same HPC queue.

Set up the Map¶

Create a Map with the donor and recipient Attitudes:
- Donor Mesh: for example a speed sweep. One Attitude is the donor and the rest are recipients.
- Donor Solve: a RANS Attitude and a DES Attitude with otherwise identical parameters, for example yaw0 and yaw0__DES. Add more pairs as needed, each recipient named after its donor.
Create a Run that uses the Map.

Set up the CFD¶

On the Run's CFD Setup tab, click the edit icon next to a recipient Attitude's name.
In CFD Attitude Setup, choose the Methodology, the donor Workflow and the Template Case:
- Donor Mesh: the same Template Case as the donor.
- Donor Solve: a DES Template Case.
Choose Save to All from the Save menu to give every Attitude the recipient setup.
Edit each donor Attitude and give it a standard (non-donor) workflow:
- Donor Mesh: a standard RANS or DES workflow.
- Donor Solve: a standard RANS workflow and a RANS Template Case.
Check that the donor and recipients use the same Queue.

Launch¶

Launch every Attitude.
When Pre-Checks have finished, start Mesh & Solve on the donor only.
- A recipient's Mesh & Solve button stays disabled, with the tooltip "Waiting for donor case to complete Mesh and Solve stage."
- Group Transitions → Mesh & Solve lists recipients as waiting and doesn't solve them.
When the donor finishes Mesh & Solve, Bramble starts every recipient that's waiting at Mesh & Solve.

There's no separate "waiting" status. A recipient stays pending at Mesh & Solve until its donor finishes. A recipient must have passed Pre-Checks to start automatically. If it reaches Mesh & Solve after the donor has finished, start it yourself.

Template Cases are shared

Other Runs may use the same Template Cases. To try a donor set-up, copy a Template Case rather than changing one that's in use.