Toyota TR010 Rear Fender Duct

REAR FENDER

WEC World Endurance Championship consistently offers interesting insights into various aerodynamic solutions. Although the technical regulations employ appropriate criteria for assessing aerodynamic performance, with the aim of ensuring close competition between cars featuring significantly different body shapes—including differences driven by the styling requirements imposed by automotive manufacturers’ marketing strategies—there is still room for engineering solutions aimed at optimising specific areas of the car.

In this brief analysis, we focus on the Toyota TR010 and a detail introduced on its rear fender.

As highlighted on several occasions, the three-dimensional shape of the fender plays a key role in controlling drag and shaping the vortex wakes that pass close to the rear wing endplates, particularly when the car is subjected to lateral acceleration and develops a slip angle.

The drawing reveals an opening in the upper surface of the fender, positioned closer to its outer edge. In plan view, the inlet has an approximately square cross-section and feeds a downward-flowing duct that terminates in the forward section of the wheel well.

The airflow captured by the inlet on the upper surface of the fender is then discharged into the upper-forward region of the wheel, approximately 30° above the horizontal diameter passing through the wheel centre.

This position within the volume between the wheel arch and the rotating tyre allows airflow to be introduced precisely in the transition region between positive and negative pressure coefficients (Cp).

If we plot the pressure coefficient (Cp) around the circumference of the rotating tyre, starting at the foremost point of the contact patch and proceeding towards the upper section of the wheel, two distinct arcs can be identified. The lower arc is characterised by positive pressure, while the upper arc, beyond the aforementioned transition point, exhibits pressure below the static pressure level.

This pressure distribution partly determines the aerodynamic drag generated by the wheel, as well as the airflow pattern within the wheel well.

The drawing above clearly illustrates outlet section position within the wheel well.

It is important to note that the portion of the wheel between the contact patch and the underfloor is exposed to the incoming airflow, giving rise to a frontal stagnation region and two vortical structures that follow tyre profile. One develops along the outer side of the wheel, while the other forms on the inner side, where it interacts with the airflow managed by the rear diffuser. This interaction can cause the vortex structure to encroach upon the diffuser flow, introducing a low-energy airflow that reduces the diffuser’s effective expansion capability.

The following drawing provides a perspective view highlighting the relative positions of the outer sidewall of the rear fender, the wheel, and the opening into the wheel well.

The airflow discharged into the upper-forward section of the wheel well is entrained downwards by the rotating tyre, helping to modify the local pressure distribution in this region in a favourable manner.

The red arrow indicates the conventional vickers wheel-arch which, like a nolder extending along the circumference of the wheel arch, introduces a lateral curvature that promotes the extraction of airflow from within the wheel well, generating a region of negative relative pressure downstream.

Ing. Riccardo Romanelli

thanx to

Yoshitaka Nakamura  @defD11

Kurisu MSub @rednaxelafx_alt

 スプ @SupremusV12RS