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High-resolution turbofan intake flow characterization by automated stereoscopic-PIV in an industrial wind tunnel environment

Ujjaini Kempaiah, K. (author), Piovesan, Tommaso (author), Zachos, Pavlos K. (author), Michaelis, Dirk (author), Gebbink, Roy (author), van Rooijen, Bart (author), Prieto, Daniel Gil (author), MacManus, David (author), Sciacchitano, A. (author), Sheaf, Christopher (author)

Unsteady inlet flow distortion can influence the stability and performance of any propulsion system, in particular for more novel, short and slim intakes of future aero-engine configurations. As such, the requirement for measurement methods able to provide high spatial resolution data is important to aid the understanding of these flow fields...

journal article 2024

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Wake and wind farm aerodynamics of vertical axis wind turbines

Huang, M. (author)

The development of offshore wind energy, especially the steps towards deep water and/or higher density wind farms, revives the prospects of vertical axis wind turbines (VAWTs). Because VAWTs may reduce the cost of floating structures, there is a potential to lower energy costs. However, VAWTs are often assumed to be less efficient and less...

doctoral thesis 2023

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On the wake deflection of vertical axis wind turbines by pitched blades

Huang, M. (author), Sciacchitano, A. (author), Ferreira, Carlos (author)

Wake losses are a critical consideration in wind farm design. The ability to steer and deform wakes can result in increased wind farm power density and reduced energy costs and can be used to optimize wind farm designs. This study investigates the wake deflection of a vertical axis wind turbine (VAWT) experimentally, emphasizing the effect of...

journal article 2023

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Experimental study of the wake interaction between two vertical axis wind turbines

Huang, M. (author), Vijaykumar Patil, Yugandhar (author), Sciacchitano, A. (author), Ferreira, Carlos (author)

Wakes and wake interactions in wind turbine arrays diminish energy output and raise the risk of structural fatigue; hence, comprehending the features of rotor–wake interactions is of practical relevance. Previous studies suggest that vertical axis wind turbines (VAWTs) can facilitate a quicker wake recovery. This study experimentally...

journal article 2023

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Boundary layer state detection using piezoelectric sensors

Stuber, V.L. (author), Kotsonis, M. (author), van der Zwaag, S. (author)

Two piezoelectric series bimorph sensors were embedded below the skin of a NACA 0012 symmetrical airfoil to detect the local state of the boundary layer during wind tunnel testing. Small vanes piercing the airfoil skin were glued onto the bimorphs providing a mechanical coupling to the local mechanical force fluctuations imparted by the local...

journal article 2022

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Multi-Δt approach for peak-locking error correction and uncertainty quantification in PIV

Adatrao, S. (author), Bertone, M. (author), Sciacchitano, A. (author)

A novel approach is devised for the quantification of systematic uncertainty due to peak locking in particle image velocimetry (PIV), which also leads to correction of the peak-locking errors. The approach, applicable to statistical flow properties such as time-averaged velocity and Reynolds stresses, relies on image recordings with multiple...

journal article 2021

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Estimation of blade loads for a variable pitch vertical axis wind turbine from particle image velocimetry

LeBlanc, B.P. (author), Ferreira, Carlos (author)

This paper presents the flow fields and aerodynamic loading of a two bladed H-type vertical axis wind turbine with active variable pitch for load and circulation control. Particle Image Velocimetry is used to capture flow fields at six azimuthal positions of the blades during operation, three upwind and three downwind. Flow phenomena such as...

journal article 2021

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Multi-Δt 3D-PTV based on Reynolds decomposition

Saredi, E. (author), Sciacchitano, A. (author), Scarano, F. (author)

A novel approach is investigated to extend the range of measurable velocities by 3D-PTV systems. The method is specifically conceived for robotic volumetric PTV measurements, but it has applications for other similar techniques. The multi-Δt method relies upon combining the information from two or more sets of double-frame images with pulse...

journal article 2020

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Uncertainty quantification in particle image velocimetry

Sciacchitano, A. (author)

Particle image velocimetry (PIV) has become the chief experimental technique for velocity field measurements in fluid flows. The technique yields quantitative visualizations of the instantaneous flow patterns, which are typically used to support the development of phenomenological models for complex flows or for validation of numerical...

review 2019

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Elimination of unsteady background reflections in PIV images by anisotropic diffusion

Adatrao, S. (author), Sciacchitano, A. (author)

A novel approach is introduced that allows the elimination of undesired laser light reflections from particle image velocimetry (PIV) images. The approach relies upon anisotropic diffusion of the light intensity, which is used to generate a background image to be subtracted from the original image. The intensity is diffused only along the...

journal article 2019

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Accurate position control of a flapping-wing robot enabling free-flight flow visualisation in a wind tunnel

Karasek, M. (author), Perçin, M. (author), Cunis, Torbjørn (author), van Oudheusden, B.W. (author), de Wagter, C. (author), Remes, B.D.W. (author), de Croon, G.C.H.E. (author)

Flow visualisations are essential to better understand the unsteady aerodynamics of flapping wing flight. The issues inherent to animal experiments, such as poor controllability and unnatural flapping when tethered, can be avoided by using robotic flyers that promise for a more systematic and repeatable methodology. Here, we present a new...

journal article 2019

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Flow Visualization around a Flapping-Wing Micro Air Vehicle in Free Flight Using Large-Scale PIV

Del Estal Herrero, A. (author), Perçin, M. (author), Karasek, M. (author), van Oudheusden, B.W. (author)

Flow visualizations have been performed on a free flying, flapping-wing micro air vehicle (MAV), using a large-scale particle image velocimetry (PIV) approach. The PIV method involves the use of helium-filled soap bubbles (HFSB) as tracer particles. HFSB scatter light with much higher intensity than regular seeding particles, comparable to that...

journal article 2018

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Rayleigh-Bénard convection of a supercritical fluid: PIV and heat transfer study

Valori, V. (author)

Fluids above the critical point are widely used in industry. Chemical, pharmaceutical, food industry and energy production are some examples. In the energy production sector they are mainly used as cooling fluids, because they allow to increase the thermal efficiency of the power plants. However, the fundamentals of their heat transfer behavior...

doctoral thesis 2018

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Peak-locking error reduction by birefringent optical diffusers

Kislaya, A. (author), Sciacchitano, A. (author)

The use of optical diffusers for the reduction of peak-locking errors in particle image velocimetry is investigated. The working principle of the optical diffusers is based on the concept of birefringence, where the incoming rays are subject to different deflections depending on the light direction and polarization. The performances of the...

journal article 2018

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PIV uncertainty propagation

Sciacchitano, A. (author), Wieneke, Bernhard (author)

This paper discusses the propagation of the instantaneous uncertainty of PIV measurements to statistical and instantaneous quantities of interest derived from the velocity field. The expression of the uncertainty of vorticity, velocity divergence, mean value and Reynolds stresses is derived. It is shown that the uncertainty of vorticity and...

journal article 2016

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On the Turbulent Mixing in Horizontal Axis Wind Turbine Wakes

Lignarolo, L.E.M. (author)

The wake flow of a horizontal axis wind turbine is characterised by lower wind speed and higher turbulence than the free-stream conditions. When clustered in large wind farms, wind turbines regularly operate inside the wake of one or more upstream machines. This is a major cause of energy production loss and a source of higher fatigue loads on...

doctoral thesis 2016

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Airfoil Self-Noise - Investigation with Particle Image Velocimetry

Pröbsting, S. (author)

Noise generated aerodynamically by the airflow over a lifting surface is often of concern for applications as diverse as air and ground transportation, heating, ventilation, air-conditioning systems, and wind turbines. The thesis describes the application of advanced optical flow measurements techniques for the visualization and description of...

doctoral thesis 2015

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Aerodynamic Mechanisms of Flapping Flight

Percin, M. (author)

The growing need for mobile aerial platforms capable of performing reconnaissance tasks and gathering intelligence in hazardous and physically inaccessible areas has given rise to an increasing interest in the development of micro aerial vehicles (MAVs), in view of their potential capabilities of versatile and highly maneuverable flight....

doctoral thesis 2015

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Experiments in stratified gas-liquid pipe flow

Birvalski, M. (author)

The growing demand for energy in the future will necessitate the production of natural gas from fields which are located farther offshore, in deep water and in very cold environments. This will confront us with difficulties in ensuring continuous production of the fluids (natural gas, condensate and water) emerging from a natural gas well. Often...

doctoral thesis 2015

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Coherent Structures in Taylor-Couette Flow: Experimental Investigation

Tokgöz, S. (author)

Taylor-Couette flow is defined as the flow confined between two coaxial cylinders which can rotate independently. Several different flow states can be observed in the gap between the cylinders by changing the rotation speeds and the rotating directions of the cylinders. The aim of this thesis is to investigate the previously reported change of...

doctoral thesis 2014