Development and application of helium-filled soap bubbles: For large-scale PIV experiments in aerodynamics

A new type of tracer is making its entry in the scenario of wind-tunnel measurements: helium-filled soap bubbles (HFSB). The present work discusses the main fluid-dynamic and optical properties of HFSB to evaluate their use for quantitative measurements in aerodynamic experiments.<br/>In the past three decades, particle image velocimetry (PIV)...

Helium-filled soap bubbles for vortex core velocimetry

Velocity measurements within the core of high-swirl vortices are often hampered by heavier-than-air particle tracers being centrifuged outside the vortex core region. The use of neutrally buoyant and lighter-than-air tracers is investigated to aim at homogeneous tracers concentration in air flow experiments dealing with high-swirl vortices...

HFSB-seeding for large-scale tomographic PIV in wind tunnels

A new system for large-scale tomographic particle image velocimetry in low-speed wind tunnels is presented. The system relies upon the use of sub-millimetre helium-filled soap bubbles as flow tracers, which scatter light with intensity several orders of magnitude higher than micron-sized droplets. With respect to a single bubble generator,...

Statistical Characterization of Helium-Filled Soap Bubbles Tracing Fidelity for PIV

The present work follows a previous study on the aerodynamic characterization of helium-filled soap bubbles (HFSBs) for large-scale PIV measurements. HFSBs were found to yield, on average, a time response of about 10s. However, the response of each individual tracer remained to be ascertained, which is the topic of the present study. The...

Large-scale volumetric pressure from tomographic PTV with HFSB tracers

The instantaneous volumetric pressure in the near-wake of a truncated cylinder is measured by use of tomographic particle tracking velocimetry (PTV) using helium-filled soap bubbles (HFSB) as tracers. The measurement volume is several orders of magnitude larger than that reported in tomographic experiments dealing with pressure from particle...

A quantitative flow visualization technique for on-site sport aerodynamics optimization

Aerodynamics plays a crucial role in many speed sports, where races are often won by fractions of a second. A thorough understanding of the flow field around an athlete is of paramount importance to optimize the athletes’ posture, garment roughness and equipment shape to achieve the minimum aerodynamic drag and maximum velocity. To date,...

Large-volume pressure from tomographic PTV in a surface mounted cylinder near-wake using HFSB tracers

A seeding system for large-scale Tomographic PIV in aerodynamics

A quantitative flow visualization technique for on-site sport aerodynamics optimization

Aerodynamics plays a crucial role in cycling as in many other speed sports. Aerodynamic investigation is required primarily for two reasons:<br/><br/>1. Optimization of the athletes' posture and equipment geometry (e.g. bicycle frame, wheels, helmet) to minimize the aerodynamic drag, thus achieving higher velocity;<br/>2. Enhancement of the...