Transportation Studies


Computational fluid dynamics (CFD) testing can reveal a tractor-trailer's level of aerodynamic efficiency.

TotalSim US, a computational fluid dynamics (CFD) consulting and solutions firm based in Dublin, Ohio, is helping the state of California certify fuel efficient and environmentally friendly tractor-trailers using resources provided by the Ohio Supercomputer Center (OSC).

For the past decade, Technical Director Naethan Eagles has been involved with CFD testing for heavy commercial vehicles, a method that is efficient in determining aerodynamic performance, drag levels and fuel efficiency. The California Air Resources Board (CARB) is interested in understanding these variables for their Tractor-Trailer Greenhouse Gas Interim Aero Device Approval Program. 

This program contributes to California’s reduction of greenhouse gas emissions by requiring tractor-trailers and their devices to meet a certain standard of efficiency to be permitted to drive within the state. In 2019, changes to the program allowed for the use of CFD testing in the certification process instead of physical wind tunnel or coast down testing, which can be more costly and less accurate than computational simulations.

“In order to have a tractor-trailer and certain devices on the trailer, those devices and the tractor-trailers much meet a certain standard laid out by California law,” Eagles said. “Manufacturers have to demonstrate that they comply with these regulations. In opening the computational fluid dynamics method as a way to evaluate those devices, it actually allows for a pretty efficient testing approach.”

TotalSim follows testing protocols and procedures outlined by CARB. If the tractor-trailer and devices meet a certain level of aerodynamic efficiency, the firm incorporates the data into the approval request form required by CARB, which is then processed by the board.

Eagles noted that OSC has been critical in allowing TotalSim to run their CFD simulations and for being able to accommodate their large workloads. 

“Over the course of the last several years, we probably have run hundreds of thousands, if not millions, of core hours at OSC, building up that understanding of how these models work,” Eagles said. 

Eagles mentioned that the accessibility and cost effectiveness of OSC has allowed this project to run smoothly.

“OSC has enabled us to do our work much more cost effectively and take on these larger projects without having to worry about the risk of investing in infrastructure that would enable us to do this in-house. We are able to use OSC as and when we need to, and it makes life so much easier,” Eagles said. “It is just a fantastic resource to have at our doorstep here in Ohio.”

TotalSim California Air Resources Board (CARB) CFD Testing