I’ve just completed the final iteration of a high-performance rear wing for Formula Student, reaching a stabilized Cl of -2.83 and a Cd of 0.80. This project focused on pushing the limits of multi-element aerodynamics using a rigorous Onshape to OpenFOAM workflow.
The Workflow:
CAD Design: Designed in Onshape using coordinate-based spline imports (CSV) for G2 continuity, ensuring the surface resolution was high enough to capture extreme pressure gradients. Pre-Processing: Utilized CfdOF (FreeCAD) to bridge the gap between CAD and CFD, managing the complex mesh-snapping requirements for small-scale features. Solver: High-fidelity simulation in OpenFOAM (blueCFD) using a refined snappyHexMesh with targeted layers on the suction surfaces. Analysis: Post-processed in ParaView to validate flow topology and force stability.
Technical Features & Optimization:
Slot Gaps & Overlaps: I performed a multi-iteration sensitivity study on the gaps and overlaps between elements, ensuring the "jetting" effect was optimized to keep flow attached on the high-camber 3rd element. Flow Control: Integrated Vortex Generators (VGs) and a Gurney Flap. The VGs were critical for energizing the boundary layer on the final element, while the Gurney flap maximized the trailing edge suction spike. Endplate Louvre Experimentation: I conducted several runs testing different Endplate Louvres (slots) to manage tip vortex interaction and pressure leakage. Interestingly, after analyzing the lift-to-drag trade-offs across various geometries, I opted to use a clean endplate for the final design, as the baseline provided the most stable aero-balance for this specific configuration.
Despite some minor trailing edge separation on the 3rd element at this extreme angle of attack, the wing provides the massive vertical load required for low-speed, high-G cornering.
The End-goal of the project was to observe various aerodynamics effects, and familiarize myself with the CAD to CFD workflow, optimizing fast design iterations, and it served as an introduction to OpenFoam and Onshape.
