skip to content

Cambridge Fluids Network


HGV aerodynamics for improved fuel efficiency

Truck in towing tank

Credit: Holger Babinsky

A 1/10th-scale model heavy goods vehicle (HGV) is tested in a water towing tank to investigate the aerodynamics of the underbody, whose flow field has not previously been studied in its entirety. The facility allows the ground condition to be replicated, while permitting optical access into the underbody.


Truck dye streak

Credit: Holger Babinsky

Flow visualisation was carried out using a dye comprising milk and water injected into the underbody. Here we see the flow, from the underside looking upwards, as it enters the front wheel-arch of the cab.

 Truck raw PIV image

 Credit: Holger Babinsky

PIV (Particle Image Velocimetry) was used to investigate the flow underneath the HGV quantitatively. Particles of TiO2 are used  to seed the flow and are illuminated with a laser plane. Images are recorded at a high acquisition rate as the model moves past the camera. The figure shows one such raw image, taken from underneath, looking upwards. Subsequent data processing can use these images to determine flow velocities.


Truck underside streamlines

Credit: Holger Babinsky

Streamlines underneath the HGV visualised as an LIC (Line Integral Convolution) image, calculated from the raw PIV data.

Formula One aerodynamics

Formula 1 wing tip vortices

Credit: Holger Babinsky

Trailing vortices behind the wing at the front of a Formula One car (one half only shown). The vortices were measured in a tow tank using Particle Image Velocimetry combined with a dedicated vortex detection algorithm.

Unsteady lift in MAVs and UAVs

Flat plate vortices jpg

 Credit: Holger Babinsky

Experiments were performed to improve understanding of the role of vortex development on unsteady lift production for micro air vehicles (MAVs) and unmanned aerial vehicles (UAVs).

These photographs show the formation of a pair of vortices behind a flat plate wing accelerating through a quiescent fluid. The structure of the vortices is revealed by injecting a dye into the flow from behind the wing, which is entrained into a shear layer that feeds the vortices. Smaller sub-vortices are visible in the shear layer due to a Kelvin Helmholtz flow instability.