Maximizing wind farm power output with the helix approach: Experimental validation and wake analysis using tomographic particle image velocimetry

Wind farm control can play a key role in reducing the negative impact of wakes on wind turbine power production. The helix approach is a recent innovation in the field of wind farm control, which employs individual blade pitch control to induce a helical velocity profile in a wind turbine wake. This forced meandering of the wake has turned...

4-D Echo-Particle Image Velocimetry in a Left Ventricular Phantom

Left ventricular (LV) blood flow is an inherently complex time-varying 3-D phenomenon, where 2-D quantification often ignores the effect of out-of-plane motion. In this study, we describe high frame rate 4-D echocardiographic particle image velocimetry (echo-PIV) using a prototype matrix transesophageal transducer and a dynamic LV phantom for...

Tomographic PIV in a model of the left ventricle: 3D flow past biological and mechanical heart valves

Left ventricular flow is intrinsically complex, three-dimensional and unsteady. Its features are susceptible to cardiovascular pathology and treatment, in particular to surgical interventions involving the valves (mitral valve replacement). To improve our understanding of intraventricular fluid mechanics and the impact of various types of...

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...

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...

The 3D separation behaviour of a micro-ramp controlled oblique shock-wave reflection: An experimental Investigation

Oblique Shock-Wave Reflections or Shock Wave-Boundary Layer interactions (SWBLI) are complex phenomena which commonly occur in high speed flight. SWBLIs can have catastrophic consequences on the aircraft due to shock induced separation and unsteadiness of the interaction. These adverse effects can be mitigated by manipulating the boundary layer,...

Geometry effect of isolated roughness on boundary layer transition investigated by tomographic PIV

Boundary layer transition over isolated roughness elements is investigated in the incompressible flow regime using tomographic PIV. Four different geometries (cylinder, square, hemisphere and micro-ramp) are considered maintaining constant height and span of the element. The main target is to compare the different flow topologies and study the...

Visualization of the structure of vortex breakdown in free swirling jet flow

In this paper we investigate the three dimensional flow structures in a free annular swirling jet flow undergoing vortex breakdown. The flow field is analyzed by means of time-resolved Tomographic Particle Image Velocimetry measurements. Both time-averaged and instantaneous flow structures are discussed, including a detailed analysis of the...

Advances in Time-Resolved Tomographic Particle Image Velocimetry

This thesis details advanced developments in 3-D particle image velocimetry (PIV) based on the tomographic PIV technique, with an emphasis on time-resolved experiments. Tomographic PIV is a technique introduced in 2006 to measure the flow velocity in a three-dimensional volume. When measurements are performed at a rate high enough to sample the...

Time-Supersampling 3D-PIV Measurements by Vortex-in-Cell Simulation

Measurement rate limitations of time-resolved 3D-3C velocity measurements by tomographic PIV limit application of the technique to small measurement volumes and low speed flows (~10 m/s). To reduce the challenging repetition rate requirements historically set by the Nyquist criterion, in the present thesis work a novel method is proposed,...

3D flow organization and dynamics in subsonic jets: Aeroacoustic source analysis by tomographic PIV

To meet the increasingly stringent noise regulation, aircraft manufacturers are searching for solutions to jet noise. This, which constitutes a significant amount of the total noise emitted by civil aircrafts, is generated by the mixing processes between the exhaust flow leaving the engine and the atmosphere. A detailed understanding of such...

Advances in tomographic PIV

This research deals with advanced developments in 3D particle image velocimetry based on the tomographic PIV technique (Tomo-PIV). The latter is a relatively recent measurement technique introduced by Elsinga et al. in 2005, which is based on the tomographic reconstruction of particle tracers in three-dimensional space from a small number of its...

Multi-pass light amplification for tomographic particle image velocimetry applications

The light source budget is a critical issue for tomographic particle image velocimetry (Tomo-PIV) systems due to its requirement for large illuminated volume and imaging at small apertures. In this work, a light amplification system based on the multi-pass concept is investigated for Tomo-PIV applications. The system design is performed on the...

Investigating the 3D Flow Structure Downstream of a Fence

In this research the experiments were performed in the water tunnel at the Laboratory for Aero and Hydrodynamics to investigate the 3D flow structure over roughness elements as a model for the flow over urban environment. It represents the first phase in an extended study on the dispersion of pollutants in an urban environment, which process is...

Motion tracking-enhanced MART for tomographic PIV

A novel technique to increase the accuracy of multiplicative algebraic reconstruction technique (MART) reconstruction from tomographic particle image velocimetry (PIV) recordings at higher seeding density than currently possible is presented. The motion tracking enhancement (MTE) method is based on the combined utilization of images from two or...