AERODYNAMICFLOWCONTROLFORROADVEHICLE PERFORMANCE ENHANCEMENTANDEMISSIONREDUCTION

Date

2026-6-22

Author

Pehlivan, Düriye Dünya

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The aerodynamic drag of heavy road vehicles is a major contributor to transportation-related greenhouse gas emissions, since overcoming aerodynamic resistance requires additional energy expenditure, leading to increased fossil fuel consumption and associated carbon emissions. To address this challenge, the flow fields around a two-dimensional D-shaped cylinder, representing a generic bluff body, and a three-dimensional square-back Ahmed body, representing a simplified road vehicle geometry, were numerically investigated using passive flow control strategies involving rigid and flexible filaments/flaps. These approaches aim to mitigate flow separation and reduce aerodynamic drag, thereby contributing to lower fuel consumption and reduced greenhouse gas emissions. Prior to the implementation of the control methods, the baseline flow characteristics of both configurations were validated against available experimental data to ensure the accuracy and reliability of the numerical approach. In the first phase of the study, aimed at developing an understanding of passive flow-control mechanisms in a simplified two-dimensional bluff-body configuration, the flow around a D-shaped cylinder equipped with rigid and flexible filaments was investigated. The results showed that rigid filaments provided slightly greater drag reduction than flexible ones, although both configurations achieved substantial reductions, up to 35%. For the flexible filaments, a flow-synchronized lock-in phenomenon was observed between the filament oscillation frequency and the wake shedding frequency. Furthermore, increasing filament rigidity was found to improve flow-control effectiveness, as stiffer filaments remained more stable under flow-induced fluctuations and maintained a more favorable interaction with the wake dynamics. In the second phase of the study, the insights gained from the two-dimensional investigations were extended to a three-dimensional square-back Ahmed body representative of a road vehicle. Two different rigid flap configurations were examined, and it was found that flaps mounted along the side edges of the vehicle base provided substantially greater aerodynamic benefits than those positioned on the upper and lower edges. Through a systematic parametric investigation, the optimum configuration was identified as an inward-deflected flap with an angle of 30°, which achieved a drag reduction of approximately 26% relative to the baseline case. The results further demonstrated the potential of passive flow control to enhance vehicle aerodynamic efficiency, leading to reduced fuel consumption and lower greenhouse gas emissions.

Subject Keywords

CFD, D-shaped Cylinder, FSI, Passive Flow Control, Square-back Ahmed Body

URI

https://hdl.handle.net/11511/120087

Collections

Northern Cyprus Campus, Thesis