A Free-Floating PIV System: Measurements of Small-Scale Turbulence under the Wind Wave Surface

Abstract An in situ free-floating underwater miniature particle image velocimetry (UWMPIV) system is developed and applied to measure the structure of turbulence in the aqueous side of the wind wave surface boundary layer. The UWMPIV system provides a direct way to measure the aqueous side turbulence dissipation rate and vortex structures immediately below the air–water interface, which are important parameters that determine the gas exchange rate across the air–water interface subjected to a low-to-moderate wind shear. The impact of platform motion on the measurement of small-scale turbulence is discussed and found to be insignificant. A series of field experiments under a near “zero-fetch” wind wave condition and one open water experiment under a low wind condition were conducted on Lake Michigan to demonstrate the capabilities of the free-floating particle image velocimetry (PIV) system. The dissipation rate estimated with a “direct method” and with a “spectra fitting” method are compared. Vertical profiles of the turbulence dissipation rate suggest a power-law dependency with depth below the water surface. Surface shear velocities estimated through the aqueous side Reynolds stress distribution agreed well with wind stresses estimated by the classic drag law for zero-fetch wind wave conditions, where the primary source of turbulence was wind shear. For the open water experiment under a very low wind condition, a high dissipation rate was observed near the water surface, suggesting a high turbulence production rate by surface waves, and the profile of dissipation rate showed a slower decay rate with depth in the presence of waves.

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Abstract 14952: Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV)

Circulation ◽

10.1161/circ.130.suppl_2.14952 ◽

2014 ◽

Vol 130 (suppl_2) ◽

Author(s):

Ahmad Falahatpisheh ◽

Arash Kheradvar

Keyword(s):

Particle Image Velocimetry ◽

Particle Image ◽

Contrast Echocardiography ◽

Ultrasound Contrast Agent ◽

Three Dimensions ◽

Small Scale ◽

High Temporal Resolution ◽

Two Dimensional ◽

Particle Image Velocimetry Technique ◽

Image Velocimetry

Introduction: The two-dimensional (2D) echocardiographic particle image velocimetry technique that was introduced in 2010 received much attention in clinical cardiology. Cardiac flow visualization based on contrast echocardiography results in images with high temporal resolution that are obtainable at relatively low cost. This makes it an ideal diagnostic and follow-up tool for routine clinical use. However, cardiac flow in a cardiac cycle is multidirectional with a tendency to spin in three dimensions rather than two-dimensional curl. Here, for the first time, we introduce a volumetric echocardiographic particle image velocimetry technique that robustly acquires the flow in three spatial dimensions and in time: Volumetric Echocardiographic Particle Image Velocimetry (V-Echo-PIV). Methods: V-Echo-PIV technique utilizes matrix array 3D ultrasound probes to capture the flow seeded with an ultrasound contrast agent (Definity). For this feasibility study, we used a pulse duplicator with a silicone ventricular sac along with bioprosthetic heart valves at the inlet and outlet. GE Vivid E9 system with an Active Matrix 4D Volume Phased Array probe at 30 Hz was used to capture the flow data (Figure 1). Results: The 3D particle field was obtained with excellent spatial resolution without significant noise (Figure 1). 3D velocity field was successfully captured for multiple cardiac cycles. Flow features are shown in Figure 2 where the velocity vectors in two selected slices and some streamlines in 3D space are depicted. Conclusions: We report successful completion of the feasibility studies for volumetric echocardiographic PIV in an LV phantom. The small-scale features of flow in the LV phantom were revealed by this technique. Validation and human studies are currently in progress.

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A New Methodology for Generation of Solitary Water Waves in Laboratory

Volume 6B: Ocean Engineering ◽

10.1115/omae2020-18537 ◽

2020 ◽

Author(s):

Xiao Liu ◽

Yong Liu

Keyword(s):

Solitary Wave ◽

Wave Height ◽

Water Waves ◽

Particle Image ◽

Fluid Velocity ◽

Simple System ◽

Wave Surface ◽

Wave Flume ◽

Image Velocimetry ◽

Laboratory Flume

Abstract In this article, a very simple system based on the enhanced dam-break flows was proposed and implemented to generate solitary wave with larger relative wave height (the ratio of wave height to water depth) in a laboratory flume. The experimental results showed that stable waves with the solitary wave profiles were successfully generated in the wave flume. The wave surface elevations were recorded by a series of wave gauges, and the fluid velocity field of the solitary wave was measured by Particle Image Velocimetry (PIV) system. The measurements of solitary wave profile, celerity and horizontal fluid velocity were also compared with the predictions by three different solitary wave theories. Results demonstrated that the present simple system was reliable and effective for the generation of solitary waves in laboratory.

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Experiments on wave propagation in grease ice: combined wave gauges and particle image velocimetry measurements

Journal of Fluid Mechanics ◽

10.1017/jfm.2019.16 ◽

2019 ◽

Vol 864 ◽

pp. 876-898 ◽

Cited By ~ 19

Author(s):

Jean Rabault ◽

Graig Sutherland ◽

Atle Jensen ◽

Kai H. Christensen ◽

Aleksey Marchenko

Keyword(s):

Wave Propagation ◽

Particle Image Velocimetry ◽

Particle Image ◽

Wave Attenuation ◽

Laboratory Data ◽

Decomposition Analysis ◽

Small Scale ◽

Wave Tank ◽

Wave Elevation ◽

Image Velocimetry

Water wave attenuation by grease ice is a key mechanism for the polar regions, as waves in ice influence many phenomena such as ice drift, ice breaking and ice formation. However, the models presented so far in the literature are limited in a number of regards, and more insights are required from either laboratory experiments or fieldwork for these models to be validated and improved. Unfortunately, performing detailed measurements of wave propagation in grease ice, either in the field or in the laboratory, is challenging. As a consequence, laboratory data are relatively scarce, and often consist of only a couple of wave elevation measurements along the length of the wave tank. We present combined measurements of wave elevation using an array of ultrasonic probes, and water kinematics using particle image velocimetry (PIV), in a small-scale wave tank experiment. Experiments are performed over a wider frequency range than has been previously investigated. The wave elevation measurements are used to compute the wavenumber and exponential damping coefficient. In contrast to a previous study in grease ice, we find that the wavenumber is consistent with the mass loading model, i.e. it increases compared with the open water case. Wave attenuation is compared with a series of one-layer models, and we show that they satisfactorily describe the viscous damping occurring. PIV data are also consistent with exponential wave amplitude attenuation, and a proper orthogonal decomposition analysis reveals the existence of mean flows under the ice that are a consequence of the displacement and packing of the ice induced by the gradient in the wave-induced stress. Finally, we show that the dynamics of grease ice can generate eddy structures that inject eddy viscosity into the water under the grease ice, which would lead to enhanced mixing and participating in energy dissipation.

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Wave-in-Deck Impact Loads in Relation With Wave Kinematics

Volume 3A: Structures, Safety and Reliability ◽

10.1115/omae2017-61406 ◽

2017 ◽

Author(s):

Jule Scharnke ◽

Rene Lindeboom ◽

Bulent Duz

Keyword(s):

Particle Image Velocimetry ◽

Particle Image ◽

Impact Load ◽

Breaking Waves ◽

Offshore Structures ◽

Small Scale ◽

Impact Loads ◽

Piv Measurements ◽

Wave Kinematics ◽

Image Velocimetry

Breaking waves have been studied for many decades and are still of interest as these waves contribute significantly to the dynamics and loading of offshore structures. In current MARIN research this awareness has led to the setup of an experiment to determine the kinematics of breaking waves using Particle Image Velocimetry (PIV). The purpose of the measurement campaign is to determine the evolution of the kinematics of breaking focussed waves. In addition to the PIV measurements in waves, small scale wave-in-deck impact load measurements on a fixed deck box were carried out in the same wave conditions. To investigate the link between wave kinematics and wave-in-deck impact loads, simplified loading models for estimating horizontal deck impact loads were applied and compared to the measured impact loads. In this paper, the comparison of the model test data to estimated loads is presented.

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Application of Particle Image Velocimetry to a Small-Scale de Laval Nozzle

AIAA Journal ◽

10.2514/2.7526 ◽

1999 ◽

Vol 37 (7) ◽

pp. 798-804 ◽

Cited By ~ 6

Author(s):

N. J. Lawson ◽

G. J. Page ◽

N. A. Halliwell ◽

J. M. Coupland

Keyword(s):

Particle Image Velocimetry ◽

Laval Nozzle ◽

Particle Image ◽

Small Scale ◽

Image Velocimetry ◽

De Laval Nozzle

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A method for three-dimensional interfacial particle image velocimetry (3D-IPIV) of an air–water interface

Measurement Science and Technology ◽

10.1088/0957-0233/20/4/045403 ◽

2009 ◽

Vol 20 (4) ◽

pp. 045403 ◽

Cited By ~ 24

Author(s):

Damon E Turney ◽

Angelika Anderer ◽

Sanjoy Banerjee

Keyword(s):

Particle Image Velocimetry ◽

Particle Image ◽

Three Dimensional ◽

Water Interface ◽

Image Velocimetry ◽

Air Water Interface

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New insights into the fine-scale structure of turbulence

Journal of Fluid Mechanics ◽

10.1017/jfm.2015.536 ◽

2015 ◽

Vol 784 ◽

pp. 1-4 ◽

Cited By ~ 3

Author(s):

Michael Wilczek

Keyword(s):

Velocity Gradient ◽

Extensive Study ◽

Scale Structure ◽

Small Scale ◽

Fine Scale ◽

Image Velocimetry ◽

Novel Variant ◽

Mean Structure ◽

Scale Turbulence ◽

Low Dimensional

In a recent study, Lawson & Dawson (J. Fluid Mech., vol. 780, 2015, pp. 60–98) present experimental results on the fine-scale structure of turbulence, which are obtained with a novel variant of particle image velocimetry, to elucidate the relation between the small-scale structure, dynamics and statistics of turbulence. The results are carefully validated against direct numerical simulation data. Their extensive study focuses on the mean structure of the velocity gradient and the pressure Hessian fields for various small-scale flow topologies. It thereby reveals the dynamical impact of turbulent strain and vorticity structures on the velocity gradient statistics through non-local interactions, and points out ways to improve low-dimensional closure models for the dynamics of small-scale turbulence.

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Aerodynamic Interactions Study on Low-Re Coaxial and Quad-Rotor Configurations

Volume 7: Fluids Engineering ◽

10.1115/imece2017-71005 ◽

2017 ◽

Cited By ~ 3

Author(s):

Dhwanil Shukla ◽

Nandeesh Hiremath ◽

Sahaj Patel ◽

Narayanan Komerath

Keyword(s):

High Speed ◽

Particle Image ◽

Small Scale ◽

Rotational Flow ◽

Coaxial Rotor ◽

Aerodynamic Interaction ◽

Image Velocimetry ◽

Stereo Particle Image Velocimetry ◽

Wake Model ◽

Free Wake

Unmanned multi-rotor VTOL vehicles have recently gained importance in various applications such as videography, surveillance, search and rescue etc. suited to their small size and relatively cheap construction. Small scale UAVs struggle in providing satisfactory performance in terms of payload, range, and endurance because of higher viscosity-dominated losses, and due to yet to be understood rotor-rotor and rotor-airframe aerodynamic interactions. Viscosity dominated rotational flow field makes most potential flow methods, such as free wake model, invalid. A full N-S based approach for this problem is too expensive. Thus, a multi-rotor aerodynamic interaction study is necessary for understanding crucial phenomena, which will help in developing physics-based models which will be instrumental in multi-rotor UAV performance prediction and design optimization. In present work, a flow visualization and a high-speed stereo Particle Image Velocimetry (SPIV) study is done on two low Reynolds number multi-rotor arrangements with the aim of capturing vortex-vortex, blade-vortex and vortex-duct interactions. The first arrangement is a coaxial rotor in forward flight and another is an in-plane quad-rotor with and without duct. Instantaneous and average PIV data is being presented here with some observations and corresponding interpretations.

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Concentration measurements downstream of an insoluble monolayer front

Journal of Fluid Mechanics ◽

10.1017/s0022112002002197 ◽

2002 ◽

Vol 472 ◽

pp. 283-305 ◽

Cited By ~ 15

Author(s):

MICHAEL J. VOGEL ◽

AMIR H. HIRSA

Keyword(s):

Surfactant Concentration ◽

Particle Image ◽

Equations Of State ◽

Second Harmonic ◽

Surface Elasticity ◽

Digital Particle Image Velocimetry ◽

Velocity Data ◽

Insoluble Surfactant ◽

Image Velocimetry ◽

Air Water Interface

The surfactant concentration distribution on a planar uniform flow with a surface-piercing barrier was measured via the nonlinear optical technique of second-harmonic generation. The measurements were performed for an insoluble surfactant monolayer on the air/water interface. A theoretical model balancing surface elasticity and bulk shear at the interface was developed to predict the concentration profile for any insoluble monolayer. Measured equations of state, relating the surface tension to the surfactant concentration, were used in the model along with velocity data obtained using boundary-fitted digital particle image velocimetry. Theoretical concentration profiles were in agreement with experimental results. Additionally, global predictions from the model for four different insoluble surfactant systems also showed agreement with experimental measurements.

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