Recently our Projects Director, Henry Pang, wrote an article for Automotive Testing Technology International magazine detailing the current challenges aerodynamicists face when working on large SUVs. Read more below.

In recent years, the booming popularity of SUVs has pushed the consumer market towards larger vehicles.  In parallel, disruptive technology companies, such as Tesla, have accelerated the electrification of road vehicles. And the advent of artificial intelligence will eventually lead to the emergence of fully autonomous, smart connected vehicles. These consumer trends, technological advancements, and a transition towards zero emissions vehicles poses several aerodynamic challenges.

Firstly, an SUV is large. Big ‘boxy’ objects tend to generate more drag. Historically, SUVs achieved drag coefficients of 0.35 to 0.45, but contemporary designs are now closer to 0.25 to 0.30. A similar trend can be said for small hatch back vehicles too. For context, the lowest drag coefficient for a production car is around 0.2 and is usually reserved for a ‘saloon’ shaped vehicle.

Henry Pang, Projects Director at Catesby Projects

A ‘convergence of design’ is starting to emerge where low drag vehicles tend to exhibit very similar features

These values are significant and have been made possible in part due to the exponential growth of computing power. Engineers can now virtually test hundreds (if not thousands) of different design iterations though the use of Computational Fluid Dynamics. The desire to lower drag coefficients has only been intensified via electrification. In an effort to alleviate range anxiety of EV vehicles, aerodynamics testing is now being utilised throughout the product development cycle – from eliminating conceptual designs, to refining the geometry in the wind tunnel.

Reducing aerodynamic drag is a virtuous cycle. A lower drag vehicle needs a smaller battery. A smaller battery makes the vehicle lighter. A lighter vehicle requires less force to accelerate. This leads to lower power requirements, reduced battery consumption and improves vehicle range even further. As drag targets become ever more audacious, the laws of physics begin to dictate what geometric shapes are possible. Thus, a ‘convergence of design’ is starting to emerge where low drag vehicles tend to exhibit very similar features.

Evidence of this is the ubiquitous hatch back roof spoiler, the proliferation of ‘boat tailing’ (narrowing of the bodywork and roof towards the rear), and the ‘squaring off’ of the rear pillars – the list goes on. This presents a unique challenge to vehicle designers. In an effort to assert brand identity and distinguish the visual design, vehicle designers will naturally prioritise aesthetics, often to the detriment of aerodynamics.

In addition, ensuring passenger comfort and practicality is advantageous. For example, large SUVs will typically favour generous headroom and boot space (which is at odds with the ‘boat tailing’ principle), thus imposing further constraints on what geometric shapes are permissible. Recently, the rise of autonomous vehicles has led to various sensors protruding out from the exterior bodywork. These devices often require direct line of sight and therefore become ‘aerodynamically intrusive’, resulting in undesirable flow separations if left unattended. Thus, the challenge for the aerodynamicist is to navigate through an increasingly restrictive minefield of subjective opinions, objective constraints and the laws of physics.

Get in touch today, to learn more about how we help improve aerodynamic performance.

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