document

Finlet rails for the reduction of the trailing-edge noise

Fiscaletti, D. (author), Lima Pereira, L.T. (author), Ragni, D. (author)

The present study focuses on the application of finlet rails as a passive technique of flow control to mitigate trailing-edge noise. Finlet rails are small cylinders whose axes are aligned along the streamwise direction, transversally positioned with respect to the trailing edge. In the first part of this study, the effects of finlet geometry...

journal article 2024

document

Advances in actuation techniques for wind farm flow control

van der Hoek, D.C. (author)

Offshore wind farms suffer substantial energy losses due to the interference of wind turbine wakes, with estimates indicating losses of approximately 10%. This thesis aims to advance the state of the art of wind farm flow control techniques for maximizing wind farm power performance. Wind farm flow control can be divided into three categories:...

doctoral thesis 2023

document

Active control of turbulent skin-friction: An experimental study

Ujjaini Kempaiah, K. (author)

A flying aircraft consumes fuel to overcome air resistance during its motion. A significant part of this consumption (55%) is due to turbulent skin friction arising at the interface of the aircraft surface and the air. The current work aims to develop and investigate relevant turbulent skin-friction reduction techniques and assist in advancing...

doctoral thesis 2023

document

Tire dependence for the aerodynamics of yawed bicycle wheels

Jux, C. (author), Sciacchitano, A. (author), Scarano, F. (author)

The aerodynamic characteristics of a modern road cycling wheel in cross wind are studied through force- and planar PIV measurements in the TU Delft Open Jet Facility. The performance of the 62 mm deep rim is evaluated for three tire profiles, and yaw angles up to 24°. All measurements are executed at 12.5 m/s (45 km/h) freestream- and wheel...

journal article 2023

document

Railway ballast

Guo, Y. (author), Jing, Guoqing (author), Markine, V.L. (author)

Railway ballast is normally made of crushed rocks with grading (particle size distributions). Ballast is inevitably suffering from more rapid degradation. Because ballast keeps undergoing and dissipating most of the train loadings, furthermore, the train speed and freight weight are increasing, causing more intensive loadings to ballast. To...

book chapter 2022

document

Pressure reconstruction from PIV measurements in the bow region of a fast ship

Jacobi, G. (author), Thill, C.H. (author), Huijsmans, R.H.M. (author)

The paper presents velocity measurements, using particle image velocimetry, as well as a reconstruction of hydrodynamic pressures for the analysis of fast ships. Stereoscopic PIV measurements with a towed underwater PIV system are conducted during towing tank tests to obtain the velocity field in the bow region of a fast ship at speeds up to...

journal article 2022

document

Pulsed LED line light for large-scale PIV -development and use in wave load measurements

Bakker, W. (author), Hofland, Bas (author), de Almeida Sousa, E. (author), Oldenziel, G. (author), Overmars, E.F.J. (author)

In this paper the development of a high-power pulsed LED line light and its use to apply particle image velocimetry (PIV) during wave impact measurements are described. An electrical circuit that generates high-current pulses is designed and built, which is used to overdrive a number of commercially available LEDs. The limit for this...

journal article 2021

document

Recent advancements towards large-scale flow diagnostics by robotic PIV

Scarano, F. (author), Jux, C. (author), Sciacchitano, A. (author)

The present work reviews the recent developments in the domain of particle image velocimetry (PIV) with attention to its use for large-scale problems of interest for industrial aerodynamics. The article introduces the fundamental principles of flow seeding for large-scale experiments based on the helium-filled soap bubble (HFSB) technique....

journal article 2021

document

Hemodynamic Study of a Patient-Specific Intracranial Aneurysm: Comparative Assessment of Tomographic PIV, Stereoscopic PIV, In Vivo MRI and Computational Fluid Dynamics

Wu, X. (author), Gurzing, S.D. (author), Schinkel, C.V. (author), Toussaint, Merel (author), Perinajová, R. (author), van Ooij, Pim (author), Kenjeres, S. (author)

Introduction: Wall shear stress (WSS) is associated with the growth and rupture of an intracranial aneurysm. To reveal their underlying connections, many image-based computational fluid dynamics (CFD) studies have been conducted. However, the methodological validations using both in vivo medical imaging and in vitro optical flow measurements...

journal article 2021

document

Cyclist Reynolds number effects and drag crisis distribution

Terra, W. (author), Sciacchitano, A. (author), Scarano, F. (author)

The Reynolds number effects on body limbs of a cyclist model, namely leg and arm, are investigated via robotic volumetric Particle Image Velocimetry measurements in the velocity range from 5 ​m/s to 25 ​m/s. The near wakes of such body limbs feature recirculation regions whose width and length are governed not only by the taper of the body...

journal article 2020

document

Contrast-Enhanced High-Frame-Rate Ultrasound Imaging of Flow Patterns in Cardiac Chambers and Deep Vessels

Vos, H.J. (author), Voorneveld, J.D. (author), Groot Jebbink, Erik (author), Leow, Chee Hau (author), Nie, Luzhen (author), van den Bosch, Annemien E. (author), Tang, Meng Xing (author), Freear, Steven (author), Bosch, Johan G. (author)

Cardiac function and vascular function are closely related to the flow of blood within. The flow velocities in these larger cavities easily reach 1 m/s, and generally complex spatiotemporal flow patterns are involved, especially in a non-physiologic state. Visualization of such flow patterns using ultrasound can be greatly enhanced by...

review 2020

document

Effect of drag reducing riblet surface on coherent structure in turbulent boundary layer

CUI, Guangyao (author), PAN, C. (author), WU, Di (author), Ye, Q. (author), WANG, Jinjun (author)

The characteristics of turbulent boundary layer over streamwise aligned drag reducing riblet surface under zero-pressure gradient are investigated using particle image velocimetry. The formation and distribution of large-scale coherent structures and their effect on momentum partition are analyzed using two-point correlation and probability...

journal article 2019

document

Understanding migratory flow caused by helicoid wire spacers in rod bundles: An experimental and theoretical study

Bertocchi, F. (author), Rohde, M. (author), Kloosterman, J.L. (author)

The core of a Liquid Metal Fast Breeder Reactor (LMFBR) consists of cylindrical fuel rods that are wrapped by a helicoidally-wound wire spacer to enhance mixing and to prevent damage by fretting. It is known that the liquid metal close to the rod is forced to follow the wires, and that liquid metal further away from the rod crosses the wires ...

journal article 2019

document

Feasibility of particle image velocimetry for low-speed unconventional vapor flows

Head, A.J. (author), Colonna, Piero (author), Schrijer, F.F.J. (author), Gallo, M. (author), Novara, M. (author)

This work assesses the feasibility of the planar PIV technique to study the characteristics of a siloxane vapor D4. Titanium dioxide (TiO2) seeding particles were used to track the motion around a rotating disk in a low speed flow. Vector fields of natural convection (NC) and a superposition of NC and rotating flow were selected as exemplary...

journal article 2019

document

Flow and heat transfer measurements in natural convection in coarse-grained porous media

Ataei Dadavi, I. (author), Chakkingal, M. (author), Kenjeres, S. (author), Kleijn, C.R. (author), Tummers, M.J. (author)

This paper reports on an experimental study of natural convection in an enclosure that is heated at the bottom and cooled at the top, filled with a packed bed of relatively large solid spheres. Nusselt numbers were measured for various sphere conductivities, spheres sizes and sphere packings for Rayleigh numbers varying between 10⁷...

journal article 2019

document

Determining effects of spacer orientations on channel hydraulic conditions using PIV

Haidari, A.H. (author), Heijman, Sebastiaan (author), Uijttewaal, W.S.J. (author), van der Meer, W.G.J. (author)

Feed spacer orientation affects the velocity pattern and pressure drop of spacer-filled channels such as those encountered in Spiral-wound Membrane (SWM) modules of Reverse Osmosis (RO). However, there are only limited numbers of experimental studies on this topic. This study sets out to reveal more detailed information on the pressure drop...

journal article 2019

document

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

Saaid, Hicham (author), Voorneveld, Jason (author), Schinkel, C.V. (author), Westenberg, Jos (author), Gijsen, F.J.H. (author), Segers, Patrick (author), Verdonck, Pascal (author), de Jong, N. (author), Kenjeres, S. (author)

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...

journal article 2019

document

Effect of surface roughness on heat transfer in Rayleigh-Bénard convection

Tummers, M.J. (author), Steunebrink, M. (author)

This paper reports on an experimental study of the effects of surface roughness on the flow and heat transfer in cubical Rayleigh-Bénard convection cells for Rayleigh numbers between 10⁷ and 10¹⁰. In the rough cells the top and bottom surfaces are equipped with square arrays of copper cubes. In line with other studies,...

journal article 2019

document

Effect of trailing edge serration-flow misalignment on airfoil noise emissions

Arce Leon, C.A. (author), Merino Martinez, R. (author), Ragni, D. (author), Avallone, F. (author), Scarano, F. (author), Pröbsting, S. (author), Snellen, M. (author), Simons, D.G. (author), Madsen, Jesper (author)

The broadband noise generated by the scattering of turbulent flow at the trailing edge of a NACA 0018 airfoil with trailing edge serrations is investigated, varying both the airfoil angle of attack and serration flap angle. Acoustic emissions from the trailing edge are measured using a microphone array. The noise level is observed to be...

journal article 2017

document

Analysis of propeller-induced ground vortices by particle image velocimetry

Yang, Y. (author), Sciacchitano, A. (author), Veldhuis, L.L.M. (author), Eitelberg, G. (author)

Abstract: The interaction between a propeller and its self-induced vortices originating on the ground is investigated in a scaled experiment. The velocity distribution in the flow field in two different planes containing the self-induced vortices is measured by particle image velocimetry (PIV). These planes are a wall–parallel plane in close...

journal article 2017