“The Impact on Scale Model Size on Results”

When it comes to differences in scale model sizes, the aerodynamic results are always a talking point. To examine the impact of scale sizes further, ARC conducted a CFD study, along with wind tunnel testing between 40 % and 50% Indycar scale models. By using the ELEMENTS CFD package, which has been validated with real wind tunnel and track testing, some interesting results were produced.

There are two significant aspects associated that must be evaluated in order to obtain reliable results. Flow similarity and accurate geometry representation. Flow similarity must be maintained around a scale model and in part is achieved by Mach number and Reynolds Number matching. Get the flow right and you get closer to accurately simulating real-world conditions.

In theory, increasing the model size does produce better resolution with the Reynolds effect issues. However, as with the operating speeds, a wind tunnel is limited by the size of the working section. Due to size limitations, blockage can become another issue.

The study found the difference in absolute lift and drag coefficients were within 3 counts between 40% and 50% scale models in ARC's wind tunnel. When development part changes were made, there was absolutely no change in delta between the model scales!

The key takeaway is, while the study shows overall results are impacted by scale size, the part change delta is the same between a 50% model as compared to a 40% model, particularly when conducting setup and body configuration changes in high downforce (worst case) configurations.

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