So far, in the series of articles, we discussed the fundamentals of a fast race car from the aerodynamics perspective and the various methods used to predict and develop its performance. This article will discuss how the race car’s aerodynamic performance on the track is analysed.
The track environment differs significantly from the controlled conditions in a wind tunnel or CFD simulation. The aerodynamic performance on the track is affected by a wide range of factors such as wind speed and direction, changing air and track temperatures, variable ride heights, varying grip levels, debris, wake from other cars and others.
Measuring aerodynamic performance on the track is far from straightforward. Pushrod/pullrod strain gauges provide an insight into the loads acting on the sprung mass; however, the resultant data has a high noise level. Even with significant treatment of the data, the variance of the measurement tends to remain too high to enable the quantification of the smaller performance deltas. In Formula 1, teams tend to run constant speed sectors during free practice as an attempt to minimise the noise, but the measurements are most often limited to straight-line.
Surface and off-body pressure measurements are a much more robust way to assess aerodynamic performance. Their signal tends to be smooth and repeatable, offering insights into the flow patterns developing around the car. These, however, cannot be used as a direct method to measure downforce or drag. Instead, they need to be analysed in combination with CFD and wind tunnel data for an indirect assessment of the aerodynamic performance.
The driver plays a vital role in the assessment of performance. Aerodynamic tests need repeatable runs (or as repeatable as possible) around the track to compare the different components. The driver’s ability to drive the track multiple times in a similar manner greatly helps the engineers to decouple other external variables from the comparisons. Furthermore, the driver’s opinion about the effect of a component on the absolute downforce levels or aerodynamic driveability of the car is often a strong factor in the decision to adopt the component tested or not.
Determining the on-track absolute aerodynamic performance, or the relative performance when comparing different components, is a complex task. We at Sabe use the analogy of “intelligence gathering” to combine measurements from various sources with the information extracted from CFD, wind tunnel and R&D to decouple some of the variables affecting the delta and ultimately build the overall picture.
In our next article, we will discuss the process of establishing the correlation levels between the track and the predictive tools.