Time-resolved tracking of a sound scatterer in a complex flow: Nonstationary signal analysis and applications

Mordant, Nicolas; Pinton, Jean‐François; Michel, Olivier

doi:10.1121/1.1477932

Cited by 22 publications

(20 citation statements)

References 24 publications

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“…The vertical component of the bubble velocity is obtained with high precision using a continuous ultrasound technique. We briefly describe this technique here, but for more detail the reader is referred to [19][20][21]. One piezo-electric ultrasound transducer positioned at the top of the vessel generates a continuous 2.8 MHz sound wave directed towards the bottom.…”

Section: Experimental Apparatus and Methodsmentioning

confidence: 99%

“…Each signal is shifted in frequency so that the emitted frequency becomes DC and hence the Doppler shifted frequency is directly proportional to the bubble velocity. In order to obtain velocity as a function of time the frequency is extracted using a numerical approximated maximum likelihood scheme coupled with a generalized Kalman filter [19].…”

Section: Experimental Apparatus and Methodsmentioning

confidence: 99%

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Force measurements on rising bubbles

Shew¹,

Poncet²,

Pinton³

2006

J. Fluid Mech.

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The dynamics of millimeter sized air bubbles rising through still water are investigated using precise ultrasound velocity measurements combined with high speed video. From measurements of speed and three dimensional trajectories we deduce the forces on the bubble which give rise to planar zigzag and spiraling motion. I. BACKGROUNDAn understanding of bubble-fluid interactions is important in a broad range of natural, engineering, and medical settings. Air-sea gas transfer, bubble column reactors, oil/natural gas transport, boiling heat transfer, ship hydrodynamics, ink-jet printing and medical ultrasound imaging are just a few examples where the dynamics of bubbles play a role (e.g [6,16,26]).We narrow our focus to a single air bubble rising through still water. The buoyant force which drives the bubble's rise does work resulting in an increase in kinetic energy of the surrounding fluid. This induced flow, in turn, gives rise to hydrodynamic forces on the bubble and hence changes in the bubble trajectory. The measurement of these forces is the aim of the experimental work presented here Our study includes a range of bubble sizes between 0.84 and 1.2 mm in radius. At the small end of this range the bubble's path is rectilinear. As the bubble size is increased, one observes a transition to a planar zigzag path [8,23]. A second instability, often preceded by the zigzag, results in a spiraling path [5,8,15,23]. For even larger bubbles, a third type of oscillating path occurs, which has similarities to the zigzag, sometimes called "rocking". We do not address this state and emphasize that it is different than the zigzag mentioned above. Unlike the zigzag state that we study, the rocking bubble undergoes dramatic shape oscillations and the frequency of path oscillation is several times higher than the zigzag or spiral [5,15]. Our approach is to use well resolved measurements of three-dimensional bubble trajectories to calculate the hydrodynamic forces on the bubbles. Other recent studies have investigated path instabilities with special attention paid to the role of the bubble's wake. Lunde and Perkins [15] used dye to observe the wake of ascending bubbles and solid particles. Brücker [5] used particle image velocimetry to study the wake of large spiraling and rocking bubbles. Mougin and Magnaudet [22,23] These studies have revealed a wake consisting of two long, thin, parallel vortices aligned with the bubble's path. One vortex rotates clockwise and the other counter-clockwise. For a spiraling bubble the wake vortices are continuously generated, while they are interrupted twice per period of path oscillation for the zigzag. Mougin and Magnaudet [22,23] observed a nearly identical wake structure in their numerical simulations (see also [24]). It is believed that the wake vortices play a critical role in generating hydrodynamic forces on the bubble.In the next section we describe the experimental apparatus and measurement techniques, as well a typical bubble trajectory. In section III, we present a method for extracti...

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Section: Experimental Apparatus and Methodsmentioning

confidence: 99%

Section: Experimental Apparatus and Methodsmentioning

confidence: 99%

Force measurements on rising bubbles

Shew¹,

Poncet²,

Pinton³

2006

J. Fluid Mech.

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“…Such techniques are rapidly being developed and improved and can be used to record tracer particle paths. Important work has been done by, for example [9,12,13,21]. Our research aims at acquiring Lagrangian statistical data using 3D-PTV in turbulent pipe flow.…”

Section: Introductionmentioning

confidence: 99%

Experimental Determination of Lagrangian Velocity Statistics in Turbulent Pipe Flow

Walpot

Kuerten

Geld

2006

Flow Turbulence Combust

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The calculation of Lagrangian statistics out of experimentally determined data from homogeneously seeded inhomogeneous turbulent flows is far from straightforward since statistical properties are position-dependent, necessitating local sampling. Two solutions for the preferential sampling of faster particles at a certain position in the flow are proposed. The performance of both methods was tested using DNS calculations for turbulent pipe flow. Both methods show a good performance for various statistical properties, thus providing two reliable ways to analyze experimental data from inhomogeneous turbulent flows.

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“…Again using arrays of acoustic transducers, a tracking method has been recently introduced to obtain independent measurements of the position and velocity of single particles in complex flows [53]. The idea is to obtain Lagrangian measurements of particle motion in complex flows.…”

Section: Lagrangian Particle Trackingmentioning

confidence: 99%

“…In order to extract the frequency modulation, standard time-frequency analysis proves to be rather ill-adapted because of the nonstationarity and low oversampling of the signal. Instead one uses a high-resolution parametric algorithm [53], which rests on the assumption that the scattered signal is a sine modulation embedded in noise (see Fig. 20b for results).…”

Section: Lagrangian Particle Trackingmentioning

confidence: 99%

Sound and vorticity interactions: transmission and scattering

Pinton

Brillant

2004

Theoret. Comput. Fluid Dynamics

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Abstract.We review several aspects of the propagation of sound in vortical flows. We restrict ourselves to isothermal, humidity-free flows at low Mach number M. Since vorticity plays a major role in vortex-flow interactions we focus on vortical flows. We consider two main canonical situations. The first concerns the transmission of sound. We analyze the evolution of acoustic wavefronts as they propagate across a single vortex. The second situation addresses the scattering of sound waves by nonstationary vortices. We study the evolution of the acoustic pressure emitted in the far field, at an angle with the initial direction of propagation. In this geometry one performs direct spectroscopy of the flow vorticity field. In each case, we review theoretical results and compare with experimental measurements and numerical simulations when available. We also briefly report how the following new acoustic techniques have recently been used to study complex or turbulent flows: time-resolved acoustic spectroscopy, speckle interferometry and Lagrangian particle tracking.

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Time-resolved tracking of a sound scatterer in a complex flow: Nonstationary signal analysis and applications

Cited by 22 publications

References 24 publications

Force measurements on rising bubbles

Force measurements on rising bubbles

Experimental Determination of Lagrangian Velocity Statistics in Turbulent Pipe Flow

Sound and vorticity interactions: transmission and scattering

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