Reducing Drag Coefficient by Over 20 Percent with Simulation

Exa PowerFLOW optimized aerodynamics of the Chrysler 200 with minimal prototypes.

Engineers at Fiat Chrysler Automobiles (FCA) used simulation-driven design to reduce the drag coefficient of the Chrysler 200 from 0.342, according to allpar.com, to 0.27.

This more than 20 percent improvement in aerodynamics was made possible with simulation iterations powered by Exa Corporation’s PowerFLOW.

The CAE software was able to assess parts of the car that would be impractical or expensive to test in wind tunnels.

The CFD solver in PowerFLOW is based on the Lattice Boltzmann Method (LBM), whereas many traditional solvers use Navier-Stokes CFD equations. Then, in addition to aerodynamics simulation, the technology can also be used to assess the turbulent flow, cabin noise and acoustics of the car.

“Our explicit solver is transient by nature and LBM achieves a very low dissipation compared to other methods based on Navier-Stokes,” stated Dr. Franck Pérot, Sr. Director for Aeroacoustics at Exa. “The results we provide are very accurate and can be obtained on any complex geometries with competitive turnaround times. Since the method is also compressible, we capture in the same simulation the turbulent flow and its acoustics radiation that propagates in the calculation domain. We also offer the capability to predict the cabin noise levels in order to assess passenger comfort.”

Using PowerFLOW, engineers can assess regions of the car that are inaccessible during wind tunnel testing, such as wheels, underbody, A-pillars, and mirrors. Using PowerFlow, engineers can predict the car’s performance and produce insights into further design improvements.

Stephen Remondi, President and CEO of Exa, said “Exa is deployed within automakers around the world, placing simulation at the heart of the automotive design process – influencing the vehicle design even as it is being conceived. This enables our customers to make more informed decisions, manage risks, reduce costs, shorten engineering timelines and ultimately deliver better vehicles to the market.”

For FCA’s Chrysler 200, the engineering team focused on the underbody, mirror and rear sections to optimize the aerodynamics. PowerFLOW helped engineers find which areas of the design contributed the most to aerodynamic drag.

“We used Exa PowerFLOW to optimize aerodynamic design from day one on the Chrysler 200,” said Dr. Kumar Srinivasan, FCA US manager. “We chose Exa‘s PowerFLOW simulation platform to optimize the vehicle’s aerodynamics. We were able to capture more data than ever before, run more tests and analyze more variations long before the first prototype of the vehicle was produced.”

Dwight Pugsley, Exa’s director of North American Automotive Sales, is impressed with the engineering FCA produced with the Chrysler 200. He said, “FCA US is at the forefront of incorporating cutting-edge aerodynamic and aero-acoustic engineering simulations into their product development process and we look forward to their innovative and efficient designs of the future.”

PowerFLOW can also be connected to third party CAE optimization software like modeFRONTIER. Using modeFRONTIER’s control nodes, engineers can automate the optimization process to further understand the design space of their designs.

To learn more about this technique, read this previous article.

Written by

Shawn Wasserman

For over 10 years, Shawn Wasserman has informed, inspired and engaged the engineering community through online content. As a senior writer at WTWH media, he produces branded content to help engineers streamline their operations via new tools, technologies and software. While a senior editor at Engineering.com, Shawn wrote stories about CAE, simulation, PLM, CAD, IoT, AI and more. During his time as the blog manager at Ansys, Shawn produced content featuring stories, tips, tricks and interesting use cases for CAE technologies. Shawn holds a master’s degree in Bioengineering from the University of Guelph and an undergraduate degree in Chemical Engineering from the University of Waterloo.