scholarly journals APPLYING PIV MEASUREMENTS ON FLOW FIELD OF WAVES PROPAGATING OVER A SINGLE SUBMERGED POROUS ELASTIC BREAKWATER

2012 ◽  
Vol 1 (33) ◽  
pp. 29
Author(s):  
Tai-Wen Hsu ◽  
Yuan-Jyh Lan ◽  
Jian-Wu Lai ◽  
Yung-Han Cheng ◽  
Shan-Hwei Ou
Keyword(s):  
Flow Field ◽  
Wave Reflection ◽  
Surface Friction ◽  
The Other ◽  
Pressure Gradients ◽  
Wave Reflections ◽  
Reflection And Transmission ◽  
Submerged Breakwater ◽  
Piv Measurements ◽  
Image Velocimetry

The objective of the present study is to investigate the flow field for waves propagating over a submerged poro-elastic breakwater. Particle Image Velocimetry (PIV) measurements were performed in wave conditions with breakwaters made of different materials. The experimental results were compared for various rigid and impermeable, elastic and impermeable, as well as poro-elastic cases. Measurements of wave reflection and transmission induced by soft and permeable submerged breakwaters are both carried out. The results show that the oscillatory motion of elastic submerged breakwater can induce extra reflective waves and result in a larger reflection coefficient. Positive (counterclockwise) and negative (clockwise) vortices are generated due to corner separation and pressure gradients. The negative vortex obtained in a poro-elastic breakwater is generated by the surface friction at the top of the structure. Because of the permeability, it is found that the negative vortex at the upstream side of the elastic and permeable case is smaller than that of the rigid and impermeable one. In contrast, the positive vortex at the downstream side of the poro-elastic case is larger than that seen with the other two cases. It is concluded that a poro-elastic breakwater would induce different wave reflections and flow patterns from those seen with the other cases due to its particular wave and structure interactions.

Two-Dimensional Experimental Investigation on the Effects of a Fowler Flap Gap and Overlap Size on the Wake Flow Field

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
David Demel ◽  
Mohsen Ferchichi ◽  
William D. E. Allan ◽  
Marouen Dghim
Keyword(s):  
Experimental Investigation ◽  
Flow Field ◽  
Angle Of Attack ◽  
Wake Flow ◽  
Two Dimensional ◽  
Edge Region ◽  
Suction Surface ◽  
Trailing Edge ◽  
Piv Measurements ◽  
Image Velocimetry

This work details an experimental investigation on the effects of the variation of flap gap and overlap sizes on the flow field in the wake of a wing-section equipped with a trailing edge Fowler flap. The airfoil was based on the NACA 0014-1.10 40/1.051 profile, and the flap was deployed with 40 deg deflection angle. Two-dimensional (2D) particle image velocimetry (PIV) measurements of the flow field in the vicinity of the main wing trailing edge and the flap region were performed for the optimal flap gap and overlap, as well as for flap gap and overlap increases of 2% and 4% chord beyond optimal, at angles of attack of 0 deg, 10 deg, and 12 deg. For all the configurations investigated, the flow over the flap was found to be fully stalled. At zero angle of attack, increasing the flap gap size was found to have minor effects on the flow field but increased flap overlap resulted in misalignment between the main wing boundary layer (BL) flow and the slot flow that forced the flow in the trailing edge region of the main wing to separate. When the angle of attack was increased to near stall conditions (at angle of attack of 12 deg), increasing the flap gap was found to energize and improve the flow in the trailing edge region of the main wing, whereas increased flap overlap further promoted flow separation on the main wing suction surface possibly steering the wing into stall.

scholarly journals On the challenge of five-hole-probe measurements at high subsonic Mach numbers in the wake of transonic turbine cascades

2018 ◽  
Vol 2 ◽  
pp. JPRQQM
Author(s):  
Marcel Boerner ◽  
Martin Bitter ◽  
Reinhard Niehuis
Keyword(s):  
Flow Field ◽  
Flow Regimes ◽  
Reynolds Numbers ◽  
Sensitivity Study ◽  
Wake Flow ◽  
Piv Measurements ◽  
Image Velocimetry ◽  
Measurement Results ◽  
Transonic Turbine ◽  
Probe Measurements

Five-hole-probes are common use in turbomachinery flow investigations, even though, inserting a probe into a flow field inevitably induces perturbations to the flow which can falsify the measurement results, especially when exposed to transonic flows. The objective of the investigations presented here is to evaluate the Mach number measurements of a five-hole-probe (5HP) in the wake flow of a transonic turbine cascade at engine relevant Reynolds numbers by comparing them to the results of particle image velocimetry (PIV). Furthermore, PIV measurements were performed with inserted probe to investigate the influence of the probe on the wake flow field. Together with a sensitivity study of 5HP measurements in flow regimes close to Ma = 1, the results demonstrate how the measurement uncertainty can be improved in high subsonic flow regimes.

scholarly journals Particle Image Velocimetry for in vitro characterization of Paravalvular Leakage of TAVR-sealing concepts

2021 ◽  
Vol 7 (2) ◽  
pp. 668-671
Author(s):  
Samuel Höing ◽  
Finja Borowski ◽  
Jan Oldenburg ◽  
Sabine Illner ◽  
Alper Öner ◽  
...  
Keyword(s):  
Particle Image Velocimetry ◽  
Flow Field ◽  
Particle Image ◽  
Aortic Annulus ◽  
Piv Measurements ◽  
Paravalvular Leakage ◽  
Transcatheter Aortic Valve ◽  
Image Velocimetry

Abstract Paravalvular leakage (PVL), defined as the leakage between the aortic annulus and a transcatheter aortic valve replacement (TAVR), is verifiably associated with short- and long-term clinical outcome, especially with increased mortality. Therefore, with the ambition to reduce or even prevent PVL of next generation TAVR, it is necessary to extend the hemodynamic understanding of PVL. This study presents an in vitro flow measurement method to localize PVL during hydrodynamic characterization of TAVR and furthermore presents different design features, socalled outer skirt, to reduce PVL. Particle image velocimetry (PIV) measurements were performed for flow field assessment during hydrodynamic characterization of TAVR. Additionally, two different sealing concepts were developed to reduce PVL. The skirts were manufactured from polymeric-nonwoven and sued to pericardium-based TAVR-prototype. The prepared TAVR-prototypes were then deployed in a pathophysiological model of the aortic root with a calcification nodule of 2 mm according to ISO 5840:2021. To assess PVL, the flow field and the regurgitation volume was measured. The PIV measurements showed a clearly visible leakage jet between the TAVR-prototypes without skirt and the pathophysiological aortic annulus model. Jet velocities of up to 0.5 m/s were measured depending on presence or configuration of a PVL-preventing skirt. When implanted in the physiological annulus model without calcification nodule, PVL was hardly recognizable. The regurgitation volume of a TAVR-prototype without skirt at 5 l/min was 36.26±1.89 ml (n = 10). The developed and manufactured polymeric-nonwoven skirts reduced PVL from 37.67±1.17 ml to 18.36±1.8 ml (n = 10, TAVR-skirt-design1) and from 46.97±1.07 ml to 17.85±1.29 ml (n = 10, TAVR-skirt-design2) at 5 l/min. The localization of PVL during hydrodynamic characterization by means of PIV was successful. The sealing concepts developed in this work were very effective and led to a PVL-reduction of the tested TAVR prototypes of about 50% to 70%.

AN AMPLITUDE STUDY ON A SEISMIC MODEL

Geophysics ◽  
1955 ◽  
Vol 20 (4) ◽  
pp. 766-773 ◽  
Author(s):  
C. S. Clay ◽  
Halcyon McNeil
Keyword(s):  
Plane Wave ◽  
Wave Reflection ◽  
Plane Waves ◽  
The Other ◽  
Seismic Events ◽  
Seismic Model ◽  
Reflection And Transmission ◽  
Conversion Event ◽  
Reflection Theory

The measured amplitudes of two seismic events which have traveled through a two layer seismic model are compared with the amplitudes calculated from plane wave reflection and transmission theory. The relative amplitudes of the events, one a dilatational‐dilatational and the other a dilatational‐to‐shear conversion event, are found to be in agreement with calculations based on reflection theory for plane waves, after correction for [Formula: see text] divergence.

scholarly journals Leading-Edge Velocities and Lifted Methane Jet Flame Stability

2010 ◽  
Vol 2010 ◽  
pp. 1-10 ◽  
Author(s):  
W. Wang ◽  
K. M. Lyons
Keyword(s):  
High Temperature ◽  
Flow Field ◽  
Reaction Zone ◽  
Leading Edge ◽  
Flame Velocity ◽  
Piv Measurements ◽  
Jet Flame ◽  
Temperature Boundary ◽  
Image Velocimetry ◽  
Partially Premixed Flame

Current interest exists in understanding reaction-zone dynamics and mechanisms with respect to how they counterpropagate against incoming reactants. Images of flame position and flow-field morphology are presented from flame chemiluminescence and particle image velocimetry (PIV) measurements. In the present study, PIV experiments were carried out to measure the methane jet lifted-flame flow-field velocities in the vicinity of the flame leading edge. Specifically, velocity fields within the high-temperature zone were examined in detail, which complements previous studies, whose prime focus is the flow-field upstream of the high-temperature boundary. PIV data is used not only to determine the velocities, but, along with chemiluminescence images, to also indicate the approximate location of the reaction zone (further supported by/through the leading-edge flame velocity distributions). The velocity results indirectly support the concept that the flame is anchored primarily through the mechanism of partially premixed flame propagation.

Numerical and Experimental Investigation of the Turbulent Flow and Mixing in a Static T-Mixer

2006 ◽  
Author(s):  
Florian Schwertfirm ◽  
Michael Manhart ◽  
Johannes Gradl ◽  
Wolfgang Peukert ◽  
Hans Christoph-Schwarzer
Keyword(s):  
Kinetic Energy ◽  
Flow Field ◽  
Turbulent Kinetic Energy ◽  
Cross Sections ◽  
Chemical Engineering ◽  
Mixing Time ◽  
Detailed Knowledge ◽  
Piv Measurements ◽  
Impingement Zone ◽  
Image Velocimetry

Turbulent mixing plays an important role in chemical engineering, especially when the chemical reaction is fast compared to the mixing time. In this context a detailed knowledge of the flow field, the distribution of turbulent kinetic energy (TKE) and its dissipation rate is important, as these quantities are used for many mixing models. For this reason we conduct two direct numerical simulations (DNS) of a confined impinging jet reactor (CIJR) at Re = 500 and Sc = 1, with and without modelling the feeding pipes. The data is compared with particle image velocimetry (PIV) measurements and it is shown that only the simulation which includes the feeding pipes gives the correct flow field. This flow field is dominated by a stable vortex in the main mixing duct. High intensities of turbulent kinetic energy and dissipation are found in the impingement zone and decrease rapidly towards the exit of the CIJR. In the whole CIJR the turbulence is not in equilibrium. The mixing of the scalar is rapid in the impingement zone, but due to the fast decrease of the turbulent intensities and due to the relaminarisation of the flow the PDFs of the scalar distributions in cross sections of the CIJR take a bimodal form after the impingement zone.

scholarly journals WAVE REFLECTION AND TRANSMISSION FOR PILE ARRAYS

1972 ◽  
Vol 1 (13) ◽  
pp. 106 ◽  
Author(s):  
Brian J. Van Weele ◽  
John B. Herbich
Keyword(s):  
Wave Height ◽  
Wave Reflection ◽  
Wave Transmission ◽  
Pile Groups ◽  
Wave Reflections ◽  
Reflection And Transmission ◽  
Wave Characteristics ◽  
Staggered Arrangement ◽  
Sea Wall ◽  
Reflection Characteristics

A group of piles in a specific geometric pattern may represent a part of a foundation supported by multiple pilings or a porous sea wall or other type of porous coastal structure. "Wave characteristics" of such a structure will include not only the wave transmission but also wave reflection characteristics. Most of the experiments in the past on pile groups were mainly concerned with wave transmission characteristics as a function of wave height and period. The main purpose of these previous studies was to evaluate the absorption characteristics of pile groups, and wave reflections were generally not measured, or evaluated. Variables in this study included wave characteristics such as wave height and length and three types of symmetric pile arrays, two providing clear spacing in the direction of the wave between pile rows and one with a staggered arrangement. The results presented in dimensionless form show the effect of pile geometry and wave steepness on the coefficient of reflection and transmissibility.

The Maximum Skin Friction and Flow Field of a Planar Impinging Gas Jet

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Adam Ritcey ◽  
Joseph R. McDermid ◽  
Samir Ziada
Keyword(s):  
Flow Field ◽  
Skin Friction ◽  
Turbulence Intensity ◽  
Reynolds Numbers ◽  
Gas Jet ◽  
Potential Core ◽  
Piv Measurements ◽  
Turbulence Transition ◽  
Image Velocimetry ◽  
Plane Jets

The maximum skin friction and flow field are experimentally measured on a planar impinging gas jet using oil film interferometry (OFI) and particle image velocimetry (PIV), respectively. A jet nozzle width of W = 15 mm, impingement ratios H/W = 4, 6, 8, 10, and a range of jet Reynolds numbers Rejet = 11,000–40,000 are tested to provide a parametric map of the maximum skin friction. The maximum skin friction predictions of Phares et al. (2000, “The Wall Shear Stress Produced by the Normal Impingement of a Jet on a Flat Surface,” J. Fluid Mech., 418, pp. 351–375) for plane jets agree within 5% of the current OFI results for H/W = 6, but deviates upward of 28% for other impingement ratios. The maximum skin friction is found to be less sensitive to changes in the impingement ratio when the jet standoff distance is roughly within the potential core length of the jet. PIV measurements show turbulence transition locations moving toward the nozzle exit with increasing Reynolds number, saturation in the downstream evolution of the maximum axial turbulence intensity before reaching a maximum peak upon impingement, followed by sudden damping at the plate surface. As the flow is redirected, there is an orthogonal redistribution of the fluctuating velocity components, and local peaks in both the axial and transverse turbulence intensity distributions at the plate locations of the maximum skin friction.

Effect of Particle Sticking on the Micro-PIV Measurement in a Micro-Bypass Channel Flow

2003 ◽  
Author(s):  
Kyung Chun Kim ◽  
Sang Youl Yoon ◽  
Ho Seung Ji
Keyword(s):  
Numerical Simulation ◽  
Particle Image ◽  
Vertical Direction ◽  
The Other ◽  
Straight Channel ◽  
Streamwise Direction ◽  
Piv Measurements ◽  
Micro Piv ◽  
Piv Measurement ◽  
Image Velocimetry

Micro-resolution Particle Image Velocimetry (Micro-PIV) was used to measure the flow in a micro-branch (Micro-Bypass). In this paper, effects of particle lump at the tip of a Micro-branch and difficulties of Micro-PIV measurements for microfluidics with branch passage were described. Micro-bypass was composed of a straight channel (200μm width×80μm height) and two branches which has 100μm width×80μm height. One of branches was straight and the other was curved. Experiments were performed at three regions along streamwise direction (enterance, middle and exit of branch) and five planes along vertical direction (0,± 10,±20μm) for the range of Re = 0.24, 1.2, 2.4. Numerical simulation was done to compare with the measurements and understand the effects of particle lump at the tip of branch.

Flow Field in the Vaned Diffuser of a Centrifugal Pump at Different Vane Setting Angles

2011 ◽  
Author(s):  
A. Boccazzi ◽  
R. Sala ◽  
P. Gaetani
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Flow Coefficient ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Piv Measurements ◽  
Setting Angle ◽  
Diffuser Flow ◽  
Absolute Mass ◽  
Image Velocimetry

Particle image velocimetry (2D-PIV) has been used for the investigation of the time averaged flow field inside the vaned diffuser of a centrifugal pump operating at best efficiency point. Pump performances and the diffuser flow field were analysed for three different vane setting angles. It was evidenced that flow coefficient at the best efficiency point decreases with the diffuser setting angle reduction. From 2D-PIV measurements in five different blade to blade planes, span-wise averaged flow angles and velocity distribution were computed. It was evidenced an influence of the diffuser setting angle on the span-wise distribution of the flow rate and of the absolute mass averaged flow angle at impeller discharge. An overturning, at the diffuser discharge was also evidenced for the two highest setting angles. 2D-PIV flow fields are presented in three different pseudo-secondary planes in order to enlighten the cross flows affecting the diffuser flow field.

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