On-site drag analysis of drafting cyclists

The aerodynamic drag of a trailing cyclists in a tandem formation is investigated at different lateral and longitudinal separations. A Ring of Fire (RoF) experiment is conducted at the Tom Dumoulin bike park of Sittard-Geleen in the Netherlands. The method is based on stereoscopic Particle Image Velocimetry (Stereo-PIV) measurements followed...

On-site drafting aerodynamics of cyclists using the Ring of Fire

Aerodynamics plays a significant role in the field of cycling as it is the dominant resistive force at racing speeds of 50 km/h. Sporting events involving multiple cyclists leads to aerodynamic interactions between the cyclists and these interactions have been exploited for performance benefits. One such aerodynamic interaction is drafting,...

Surface Pressure Measurements using Coaxial Volumetric Velocimetry: Investigation on an Inverted Wing in Ground Effect

In experimental aerodynamics, pressure is an important parameter which provides insight into the various features of the flow around the test object. By obtaining the surface pressure information, various inferences can be drawn such as flow separation, local flow velocity etc. Traditionally, the most common method of obtaining pressure has been...

Accuracy assessment of the Ring of Fire system for on-site aerodynamic drag measurements

The continuous pursuit of reducing drag in many speed sports, such as cycling and ice-skating, demands novel approaches to gain further insight into flow phenomena around athletes. In recent years, the Ring of Fire measurement technique has emerged as a feasible option to visualise and analyse flow structures of transiting objects based on...

Investigation of Footballs Wakes by Robotic Volumetric PIV

The robotic volumetric PIV system of the TU Delft is proposed to be used to gather quantitative data in the wakes of footballs. For over a decade now, a new football is introduced every FIFA World Cup. The varying surface characteristics affect the behaviour of the footballs in flight, and so football aerodynamics has become subject to increased...

Time-averaged pressure from Robotic Volumetric PIV

Pressure represents a physical magnitude which allows the characterisation of flow behaviour. Its study is<br/>of great interest for engineering purposes and is broadly reported in the literature. The practical implementation of pressure measurements in industrial wind tunnel facilities involves the use of intrusive pressure probes only able to...

Advances and assessment of the Ring of Fire concept for on-site cycling aerodynamics

Aerodynamics investigations in speed sports generally consist of measurements of aerodynamic loads through wind tunnel experiments. Lately, a new technique has emerged, known as the Ring of Fire. It is the only drag measurement technique capable of retrieving flow field data on-site, by using Large-Scale PIV. In this Ring-of-Fire project a Low...

Coaxial volumetric velocimetry

This study describes the working principles of the coaxial volumetric velocimeter (CVV) for wind tunnel measurements. The measurement system is derived from the concept of tomographic PIV in combination with recent developments of Lagrangian particle tracking. The main characteristic of the CVV is its small tomographic aperture and the...

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)...

Generation and control of helium-filled soap bubbles for large-scale PIV

The operating regimes of an orifice-type helium-filled soap bubbles (HFSB) generator are investigated to characterize the properties of the resulting tracers. The geometrical properties of the bubbles as well as the production rate are studied with high-speed shadowgraphy. The weight of the tracers relative to the mass of displaced air is...

Volumetric measurements of a self-similar adverse pressure gradient turbulent boundary layer using single-camera light-field particle image velocimetry

As a novel volumetric particle image velocimetry technique, single-camera light-field PIV (LF-PIV) is able to reconstruct three-dimensional flow fields with a single camera. The merits of LF-PIV lie in its concise hardware setup and minimum optical access requirement, its capability has been proved in many flow scenarios. In this study, LF-PIV...

An assessment of the Ring of Fire approach for indoor and outdoor on-site sports aerodynamic investigation

A procedure is proposed to reconstruct the instantaneous velocity field from full particle trajectories in a data assimilation framework that includes the vorticity transport equation. The technique is christened as time-segment assimilation (TSA). The work addresses the common problem of low seeding concentration in 3D experiments, usuallThe...

On the use of full particle trajectories and vorticity transport for dense velocity field reconstruction

A procedure is proposed to reconstruct the instantaneous velocity field from full particle trajectories in a data assimilation framework that includes the vorticity transport equation. The technique is christened as time-segment assimilation (TSA). The work addresses the common problem of low seeding concentration in 3D experiments, usually...

Drag resolution of a PIV wake rake for transiting models

The accuracy of the “PIV wake rake” method to measure the drag of transiting objects is evaluated. Tomographic Particle Image Velocimetry measurements are conducted on a sphere towed at different speeds, within a Reynolds number range where the drag coefficient is constant. In contrast to PIV wake rake application on steady models in wind...

Bridging PIV spatial and temporal resolution using governing equations and development of the coaxial volumetric velocimeter

A series of techniques is proposed for volumetric air flow measurements that are based upon the principles of particle image velocimetry (PIV). The proposed techniques fall in two categories; part 1 of this dissertation considers measurement data processing using constitutive laws and part 2 focuses on development of a coaxial volumetric flow...

Aerodynamics of transiting objects via large-scale PIV - the Ring of Fire Concept

A novel measurement system, the Ring of Fire, is deployed which enables the aerodynamic drag estimation of transiting cyclists. The system relies upon the use of large-scale stereoscopic PIV and the conservation of momentum within a control volume in a frame of reference moving with the athlete. The rider cycles at a velocity of approximately 8...

Aerodynamic drag of a transiting sphere by large-scale tomographic-PIV

A method is introduced to measure the aerodynamic drag of moving objects such as ground vehicles or athletes in speed sports. Experiments are conducted as proof-of-concept that yield the aerodynamic drag of a sphere towed through a square duct in stagnant air. The drag force is evaluated using large-scale tomographic PIV and invoking the time...

Vortex velocimetry of air flows using Helium Filled Soap Bubbles (HFSB)

This thesis work illustrates the first of its kind solution to this problem of lack of seeding at vortex core in air flows, by the use of Helium Filled Soap Bubble (HFSB) which is a neutrally buoyant tracer particle in air flows. To analyse the lack of seeding in the vortex core, a 2D numerical simulation of particle motion in vortex flow is...