Many different CFD programs are available on the market. Each breaks up the flow field into several million elements of varying size. The Navier-Stokes equations are solved for each of these elements hundreds or even thousands of times to determine an accurate representation of the steady-state flow of air over or through the vehicle. The advent of relatively inexpensive but extremely powerful computing has put CFD analyses capability onto high-powered desktop processors. As did VW for their simulations, I used the popular ANSYS Fluent CFD program for my land speed record analyses.
Some advantages that I found using CFD in an aerodynamic design study include:
- The ability to make rapid design changes without having to produce new models for the wind tunnel
- Specification of a moving road surface in CFD that was not possible with the wind tunnels available
- Ability to easily examine effects of rotating wheels using CFD
- The ability to change the air density, replicating the reduced air density at the Bonneville altitude
- Easy visualization tools to examine airflow around various parts of the bodywork
- Ability to separate out the effects of airflow on individual components and bodywork structures
- Ability to examine the effects of pitch and yaw of the vehicle on the aerodynamic forces generated
Driver Romain Dumas has already been testing the Volkswagen I.D. R Pikes Peak in Europe. Dumas is a three-time winner at Pikes Peak. The car weighs just 2,425 pounds, very light for a battery electric racecar. The front and rear axles each have an electric motor, providing all-wheel drive. The car’s top speed of 155 mph isn’t particularly fast for a sports prototype—an indication that the engineers are concentrating on cornering speed and not drag reduction. In any case, the sinuous Pikes Peak course, with more than 156 turns, places an advantage on acceleration and cornering over raw top speed.
I was able to set four FIM World Land Speed Records at Bonneville in 2017, thanks in large part to the CFD aerodynamic studies that I undertook. I have every reason to expect, given a generous helping of luck, that Volkswagen will be successful with its CFD optimized design and in its record attempt this year at Pikes Peak. As a fan of developing aerodynamic solutions using CFD, I’ll certainly be cheering for them.
Design News Senior Editor Kevin Clemens will be presenting "Faster With Electrons: Breaking EV Land Speed Records" at the Open Tech Forum of the September 11-13 Battery Show in Novi, Michigan.
Senior Editor Kevin Clemens has been writing about energy, automotive, and transportation topics for more than 30 years. He has masters degrees in Materials Engineering and Environmental Education and a doctorate degree in Mechanical Engineering, specializing in aerodynamics. He has set several world land speed records on electric motorcycles that he built in his workshop.
|The EV & HV Info You Need Now. Join our in-depth conference program to learn about topics from new developments in electric motor design to regulations and rollout timelines. The Electric & Hybrid Vehicle Technology Expo. Sept. 11-13, 2018, in Novi, MI. Get registration info for the event, hosted by Design News’ parent company UBM.|