June 14, 2018

An Examination of the Future of Truck Aerodynamics

Demand for fuel-efficient trucks has never been higher in our current climate…

Demand for fuel-efficient trucks has never been higher in our current climate of sustainability and spend reduction. Since aerodynamic truck design has a critical impact on fuel efficiency, it’s vitally important that truck designers focus on aerodynamics to boost environmental-friendliness and lower operational costs.

A lot has been discussed in the media recently about the next generation of Class 8 tractor designs and how they will seek to improve aeroefficiency – and therefore reduce costs – for the fleet sector in years to come.

Challenges Designing Aerodynamic Trucks

When designing a truck, manufacturers want to consider styling, passenger space, and component packaging needs, not just aerodynamics. When they’re refining the exterior shape, that’s when they contemplate angles, radii, and dimensions for aerodynamic efficiency. Typically, aerodynamic improvements can be made with minimal impact on the styling aesthetics. As the truck design progresses further, aerodynamic elements like spoilers, wheel deflectors, and underbody covers are added around the costs of parts and other constraints. Throughout the design process, adequate cooling flow to the heat exchangers must be maintained while minimizing the associated wind resistance.

The main challenge faced during the truck design process is that aerodynamic information can be costly and difficult to obtain. This is because, traditionally, truck designers would have to build detailed modesl or prototypes of trucks and test them in wind tunnels. This can only happen at late-stages of the design process, and therefore it’s extremely difficult, time-consuming, and costly to make large-scale changes to the design. This type of testing for aerodynamic efficiency is a major contributor to truck development costs and design cycle time.

Using Aerodynamic Simulation to Optimize Truck Design

Aerodynamic simulation is a cost-effective alternative to model and prototype testing. Simulation changes the vehicle development process by reducing development costs and design cycle time. Additionally, simulation can bring feedback about the design performance into each stage of development, helping truck designers understand the aerodynamics of their designs at all times.

Furthermore, aerodynamic simulation is more accurate than physical tests, because of it can capture small details otherwise missed physical reduced-scale models. Simulations can also duplicate incredibly accurate real-world road conditions which might damage wind tunnels if physically recreated.

Finally, simulation can reduce the cost of the development process by revealing design improvements early in the design phase so that designers can develop solutions that do not require additional parts and expense to the vehicle.

The Nikola One: An Aerodynamic Electric Truck Design Concept

Of particular interest recently has been the Nikola One concept truck from Utah-based startup, Nikola Motor Company, for its eye-catching cabin design and stated ‘one million miles of free fuel’. Further intrigue lies in its commitment to ‘never plugging in’ for electric charge, as it utilizes clever regenerative braking and active turbines to refuel the huge 320 kWh battery onboard.

More than 32,000 individual lithium-ion cells that are mainly charged on board by a turbine that can be powered by a range of fuels contribute to the Nikola One’s bold claim of 1,200-mile electric range.  This figure would be significantly reduced were it not for the aerodynamically efficient arrow-head shaping of the cabin.

The turbine-electric drive system allows more flexibility for the vehicle layout than a traditionally-powered Class 8 tractor that typically has to package the diesel engine in front of the cabin.  This flexibility allows the designers to focus on the driver experience as well as open up the design space to unlock significant aerodynamic improvements.

Rather than a traditional, vertical windshield and grill, the Nikola One has a single sweep side profile from the bumper to the exit of the roof fairing to allow passing air to glide over the top of it with reduced aerodynamic disturbances.  The top view profile shows softer radii in the traditional A-pillar area that cleanly transitions to the wheel arches, all combining to reduce drag inducing separation in all types of wind conditions compared with traditional tractor hood and cabin design.

At the front of the cabin and on the side skirting behind the front wheels, strategically placed vents suck in the oncoming airflow to help with the thermal management of the electric-turbine drive system while also enhancing aerodynamics, necessary for the Nikola One’s prolonged electric range. These passive aero-thermal performance methods will allow the truck to haul its load efficiently and improve the robustness of the vehicle design and operation.

Final Thoughts

The Nikola One remains merely a concept at this stage – and perhaps that’s why its creators can make such assertions about its efficiency – but highly efficient, highly slippery electric heavy duty tractors are being taken seriously by industry leaders as well.

Tesla CTO and co-founder, JB Straubel, recently teased audiences on the billion-dollar brand’s interest in developing trucks of similar capabilities to the Nikola One:

“I can’t say too much about the new products and the things we are developing, but from a pure technology point of view, everything that we’ve done on vehicles translates directly into trucks. There’s no reason that today you can’t make a very compelling electric truck. They can charge at same sort of times as a Model S – as one of our passenger vehicles – and have the same economy of operation.”

Learn more about improving truck aerodynamic design using simulation software. 

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