Road Vehicle Drag reduction Using Wind Tunnel Testing
Project Overview
The aim of this project was to investigate the effectiveness of nearly rigid self-excited flags in reducing the base drag of large road vehicles, using an Ahmed model. Wind tunnel experiments were conducted to explore how flag stiffness, placement and geometry influenced wake dynamics and overall drag reduction on HGVs.
Tools & Technologies
- Wind tunnel testing
- Aerodynamics
- 3D CAD modelling
- Data Acquisition
- Data processing
- Data analysis
Project Details
Heavy goods vehicles (HGVs) contribute over 25% of road transport emissions and 6% of total greenhouse gas emissions in the EU. At speeds above 100 km/h, aerodynamic drag becomes the dominant resistance, accounting for ~50% of total resistance and up to 65% of fuel consumption.
This project investigated passive flow control using nearly rigid self-excited flags to reduce base drag. Wind tunnel experiments were conducted at Re = 150,000 using a modified Ahmed body with 0°, 20°, and 35° slant angles to represent different flow regimes.
Flags with varying stiffness (0.05 mm and 0.25 mm) and non-dimensional lengths (Lf/H = 0.10–0.65) were tested at multiple mounting locations. Results showed that more rigid flags improved wake interaction and delayed flow separation, while flexible flags increased turbulence and drag.
Maximum drag reduction of 2.63% was achieved at 20° slant angle using rigid flags, with ~2% reduction at 35°. Performance was linked to synchronization between flag oscillations and wake structures (Strouhal effects), demonstrating the potential of passive aerodynamic devices for HGV efficiency improvements.
Key Results
- Up to 2.63% drag reduction achieved
- Rigid flags outperformed flexible designs
- Wake synchronisation improved aerodynamic efficiency
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