Test The Limits

How Autonomous Vehicle Technology is Impacted by Aerodynamics

By Brad Duncan

May 18 2015

The emergence of autonomous cars will present many interesting technical challenges, not the least vehicle aerodynamics. Due to the nature of the problem, many of the aerodynamics challenges will have to be addressed using simulations.

The technology is developing fast. We have seen prototype autonomous cars licensed for use on roads in the United States as well as Europe, and, as of May this year, the state of Nevada has given permission for the first autonomous 18-wheeler truck to drive on its roads.

We have recently worked with a client on a study looking at a very important aspect of autonomous driving – that of caravanning, or platooning. This is where you link up trucks wirelessly on the highway and let the first vehicle deflect the air around the second and third to lower the net wind resistance, represented by aerodynamic drag coefficient, CD, of each of the trucks in the platoon. The computer controlling the autonomous driving can push the trucks closer together than a human can drive them, in effect creating a train and substantially improving the fuel economy.

This study helped us determine the optimal distance between the trucks because if they’re too close then the second engine doesn’t get enough air to be cooled properly. There’s an optimal gap that provides sufficient airflow through the grille while it provides significant drag reduction.

This isn’t to say that aero devices should be dumped for trucks. You’d still need to reduce drag individually for solo trips, and because it would be hard to logistically figure out which is the lead vehicle or trailing vehicle. But perhaps eventually there will be a different dimension to aero engineering given the amount of fuel that platooning would save. The shape of aero devices will be affected if they would be designed with platooning in mind.

It’s not just trucks benefiting here. Car fuel economy would also benefit from platooning. Their design would be affected as well in order to maximize the benefits of aerodynamic drag reduction.

We’re just starting to understand the implications of autonomous driving. Elon Musk, the head of Tesla, has said that driving will eventually become illegal as computers do the job better than we do. He has a good point since ninety percent of the road accidents are caused by human mistakes. That would radically change their design and we as aerodynamic specialists are already thinking about the challenges this scenario presents.