On the first day of F1 testing, Red Bull dedicated part of its on-track work to aerodynamic correlation between simulation environments and real-world data. Unlike other teams, the Austrian squad did not use complex Pitot tube structures. Instead, they opted for a simpler and more cost-effective approach: paraffin. This method, known as flow-viz or “flow visualization,” involves applying a highly viscous, brightly colored fluid to the car, which, when in motion, highlights the airflow patterns.
This data can also be obtained through CFD simulations, and the experimental and theoretical findings are then compared. The analysis is mainly visual, relying on images captured from the track, but it is highly effective. Red Bull applied the paint to various sections of the F1 car, starting from the front suspension area up to the floor attachment, then on the anti-intrusion cone, and finally on the sidepods and floor, particularly the diffuser.
F1, Red Bull analyzes the RB21
Let’s start with the first graphic, where we highlight the general flow pattern using purple arrows. We can see that just ahead of the floor intake, the airflow undergoes a strong up-wash effect. This is intentional, as the flow is naturally drawn into the floor due to the lower pressure. Once past the floor’s leading edge, the fluid enters a down-wash phase, being pulled downward toward the car. At the intake, the flow splits: one part enters the opening at a certain angle, while the other continues its down-wash trajectory.
The fluid then appears to stop, but small streaks indicate that it remains closely attached to the lower sidepod surface. It’s worth noting that Red Bull’s characteristic curve at the intersection between the sidepod and the floor is less linear compared to other cars. The yellow line highlights the sidepod shapes, showing a slight up-wash in this area. However, overall, the flow remains fairly attached to the bodywork and does not appear too turbulent. Comparing last year’s flow-viz tests on other cars, this area previously showed much more chaotic airflow.
In the next image, we see confirmation of this observation. This test was done in a subsequent run, but the story remains the same. The anti-intrusion cone acts as a ramp guiding the airflow downward. In Red Bull’s case, its cover is less bulky than Ferrari’s. The fluid is drawn toward the sharp edge of the floor. At the point where the “Castore” sponsor logo is located, there are small unpainted areas, which could indicate partial flow separation, but this is difficult to confirm. Normally, such separation would be visualized differently using flow-viz.
The Milton Keynes team then shifted its focus to the rear section, applying paint across the entire upper surface of the beam wing and parts of the floor, both on the upper and lower sides. Observing the sidewall of the diffuser, we see a local down-wash effect that tends to generate a vortex as the airflow tries to enter the diffuser volume. Additionally, the inner edge of the diffuser was examined from two different angles.
F1, Red Bull and the possible fluid separation
This type of surface shaping should be highly beneficial in extracting a greater volume of air while ensuring that the airflow remains attached to the car’s body. However, there is a small area where the flow detaches, marked by a purple circle. It’s interesting to see that some of the paint also ends up on the beam wing, highlighting the strong aerodynamic synergy between these two elements that the Austrian F1 team has achieved.
Finally, thanks to the last image in this analysis, we can observe the so-called mouse-hole, which allows us to track the movement of certain fluid masses. Although small, this opening—present on Red Bull and other F1 cars—plays a crucial role. It helps re-energize the airflow passing through the diffuser while also increasing the volume of air interacting with the extractor. The final result: an overall increase in downforce.
Leave a Reply