Approximately 40 body shapes were examined which included different sets of features. Lift, drag, moment results were recorded for each. As necessary, set up parameters such as speed, ride height, pitch, and yaw were varied as follows:
- speed: 17, 30, 45 m/s
- ride height: 0.5, 1, 2, 3 inch clearance between the road and the diffuser lower plane
- pitch angle: -1, 0 +1 degrees (due to low ride height, greater pitch angles cause contact between road and diffuser)
- yaw angle: 0, 15, 30 degrees
(3D solid) evolution. +30 bodies examined. This includes examination of an upper-limit case, the body examined is a NACA 6522 Wing-in-ground-effect with planform identical to that of the car, and ends plates sealing the sides. This produce a total downforce of 57kN with a Cl/Cd of ~12.
Graphical results examples: pressure contours, streamlines, vectors.
Numerical results: forces and torques (pressure and viscous), Cd Cl values
Wheel Boundary
Race Car CFD Analysis
The analysis process presented is an iterative study of the flow field around an open-wheeled race car body. The goal of the exercise was to improve the aerodynamics performance of a baseline model.
Analysis Process
Many cycles were completed, and during the initial stages, the single cycle process parameters were tuned to improve modelling fidelity. Finally, process parameters were fixed, and the car aerodynamic boundary became the only variable of the investigation.
Some examples of process parameters are shown below, click the images for more info.
Graphical results examples: pressure contours, streamlines, vectors. Click image for more info.
Physics Settings
Road Mesh
Road Boundary
Aerodynamic Boundary Evolution
The body began as a very basic shape and evolved to much more complex. The initial body did not posses any common aerodynamics features except a flat bottom. As complexity increased, aerodynamics features were added. The baseline body has 4 basic features:
- flat bottom
- positive body rake (pitched forward)
- front splitter
- rear diffuser
Initial values for these aerodynamic features were selected from similar application found in literature.
The baseline model includes cockpit details, exhaust details, radiator duct, and other parts that extend beyond the closed body work which could have a significant impact on aerodynamics. These features are included in a de-featured style, meaning small geometric details which would impose a significant computational cost, but would otherwise have negligible impact on the results, are not included.
The following set of images provides some examples of body shapes that were examined. Some features appear only on the left side since a mirror plane was used to simulate the right side. Click the images to for more info.
The final solution chosen for the car build is body 036 without wings for the initial build, with wings being added as time allows.
The aerodynamic data collected for body 036 is used to calculate parametrized data for rFactor2 physics model. Once complete, the rFactor2 model will be publically available. The update with wings will also be made available once complete.
Numerical results, click images for more info.
Performance Limit
In order to gauge how well the various body shapes were performing, the performance limits for the given planform and frontal area were estimated using a best case concept. The desired performance metric are:
- downforce value on the order of magnitude of the vehicle mass
- large Cl/Cd ratio
Therefore the concept body chosen which would likely maximize these metrics was a NACA 6522 Wing-in-ground-effect (WIG) with ends plates sealing the sides. Both the planform and the front area are identical to that of the car. At 30m/s, this produce a total downforce of 7kN with a Cl/Cd of ~14.