By: Clare Maloney, Embry-Riddle Communications Student
As a school with the word “aeronautical” in its name, it came as no surprise that the Embry-Riddle Aeronautical University (ERAU) EcoEagles had extensive aerodynamic modifications at the EcoCAR 2 competition this past May.
Among the modifications the EcoEagles researched or implemented into their vehicle were: vortex generators on the rear roof, aerodynamic wheel covers on each wheel, flexible side skirts on the undercarriage, and slot jets on the rear trunk lid. The slot jet modification promised the greatest potential gains as indicated through an initial investigation by team member Domenic Barsotti showing initial results of a 26 percent reduction of the coefficient of drag. To confirm these results, Barsotti and his advisor, Dr. Sandra Boetcher, were able to team up with Argonne National Laboratory’s Transportation Research and Analysis Computing Center (TRACC) to perform higher fidelity simulations.
Barsotti initiated his research by using an Ahmed body that that is commonly used in research applications to perform low-fidelity initial vehicle simulations at a low computational cost. Barsotti used commercial computational fluid dynamics (CFD) software, called Star-CCM+, to simulate the Ahmed body as an analogue for the actual vehicle body both with and without the proposed novel slot jets.
Air flows over the vehicle initially in what is called a laminar flow and disperses into turbulent air called wake vortices. A laminar flow occurs when a fluid, flows in parallel layers with little turbulence between the layers of air flow. When the air flow reaches the back of the vehicle, the air disperses into numerous, uncontrolled mini-vortices that creates a wake structure and adds a considerable amount of drag to the vehicle. Slot jets inject air at a controlled velocity into the air flow and cause the structure to reform in a lower drag configuration. Initial results on the Ahmed body demonstrated success, but to validate it the team needed to run the simulation on the actual Malibu model.
Argonne enabled the team to test this aerodynamic modification by allowing the students access to their TRACC cluster. Using the TRACC cluster the team was able to simulate the full Malibu model with slot jets in different configurations. Through the use of proper orthogonal decomposition (POD), the team was able to apply the software Mathcad to analyze the airflow into comprehensible arrangements based on their kinetic energy created by the slot jets. First results from the TRACC cluster indicate that these slot jets are less efficient on the actual Malibu model than the Ahmed model, but still promise significant improvements to the efficiency of the vehicle.
Although the work is still in progress, Barsotti was able to use this research as his thesis work to graduate and start a career in professional CFD analysis with CD-adapco. The EcoEagles and Dr. Boetcher are looking forward to continuing their research in the coming year and potentially implementing the slot jets onto their Chevrolet Camaro for EcoCAR 3!
Categories: Under the Hood