Testing geometries over multiple flow conditions is an effective method of producing more robust designs. Where these flow conditions are changes in boundary conditions, such as velocity or yaw angle, it is not necessary to regenerate the mesh for each test. Time and money can therefore be saved by reusing the mesh from one of the tests in all the others.
Introducing Donor Workflows
The ability to clone a mesh from one simulation to another is called a ‘Donor Workflow’ in bramble. Using this workflow is as simple as selecting it from a drop-down. All the complexities of cloning the mesh is handle by bramble automatically.
It is possible to clone a mesh and re-use it to run a RANS or DES simulation, and also to clone a RANS simulation and use it to run a DES solve.
As an example, we will show you how to setup and run a mesh cloning example for a yaw sweep.
Step 1 – Create a Map
In bramble, you have the ability to define a Map, a set of test conditions over which a design is to be tested. From the ‘Maps’ view, we select ‘New Map’ and then define out test conditions. In this example we will run five different yaw angles.
Step 2 – Create a Run
Assuming we have a baseline case, we can simply select ‘Create Child’ on the baseline, and then ensure that our new map is chosen. bramble will create a copy of the baseline, duplicating all the model build and CFD setup information.
The run will be populated with lifecycles for each of the test conditions, or attitudes, in the selected map.
Step 3 – Update CFD Workflows
From the CFD Setup tab, we can select the appropriate workflows. One attitude will be configured with a standard RANS workflow. This will be the attitude from which the mesh will be cloned. All the other attitudes will have a RANS Donor workflow selected.
Step 4 – Launch Simulations
Finally, we can launch all the simulations as we would normally. Once Pre-Checks have completed, and assuming there are no issues flagged, the attitudes will be ready to submit to the cluster.
The important difference with the Donor Workflow is that only the standard workflow attitude (the one that will be cloned from) can be submitted at this point. The other attitudes will have their ‘Mesh & Solve’ buttons deactivated as they cannot be launched until the first attitude has completed and we have a mesh.
When the first attitude completes its solve, however, bramble will automatically submit the other attitudes for solving – you do not have to worry about doing this.