A particle-image based wave profile measurement technique

Mukto, Moniz; Atmane, Mohamed A.; Loewen, Mark

doi:10.1007/s00348-006-0226-6

Cited by 15 publications

(17 citation statements)

References 7 publications

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“…Like in [8][9][10], the camera was positioned below the level of the interface and it was set at an angle of approximately 16 degrees, looking upwards underneath the waves (Figure 1, right). This position was necessary to image the whole liquid layer, including the interface, and to avoid any blocking of the view due to waves.…”

Section: Figure 1 Experimental Setup Schematic View (Left) and A Cromentioning

confidence: 99%

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PIV measurements of waves and turbulence in stratified horizontal two-phase pipe flow

Birvalski

Tummers

Delfos

et al. 2014

International Journal of Multiphase Flow

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The technique for obtaining detailed velocity fields in a wavy liquid layer in stratified air/water pipe flow is described in this paper. By combining Particle Image Velocimetry (PIV) with an interface detection technique, the velocity field is resolved in the whole liquid layer. Furthermore, since the shape of the interface is resolved at each time instance, this information is used to conditionally average the velocity field according to the wave phase, which results in phaseresolved velocity profiles. These velocities are then used to separate the wave-induced motion from the turbulenceinduced motion in the liquid layer. In this way, the turbulent wavy regime is analysed. The results of the measurements are compared to the theory of waves and turbulence.

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Section: Figure 1 Experimental Setup Schematic View (Left) and A Cromentioning

confidence: 99%

“…Several studies [8][9][10] report on techniques that simultaneously acquire the velocity field (by using PIV) and the interfacial profile in flumes or wind-wave tanks. In these studies, two cameras are used: one for capturing PIV images and another that records the interface shape.…”

Section: Introductionmentioning

confidence: 99%

PIV measurements of waves and turbulence in stratified horizontal two-phase pipe flow

Birvalski

Tummers

Delfos

et al. 2014

International Journal of Multiphase Flow

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“…In our set-up, only one camera was used for both the subsurface velocimetry and interface detection purposes, contrary to Mukto et al (2007). This choice was guided in part by the presence of a large number of water droplets at the higher gas flow rates investigated.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…The accuracy of the present method was assessed using simulated wave profiles as in Mukto et al (2007). Those were defined by:…”

Section: Error Analysis and Limitationsmentioning

confidence: 99%

“…Detection of the maximum intensity gradient was performed for each column of pixels, and outliers were removed using least-square regression and a statistical criteria. Mukto et al (2007) recognized that a second camera was needed, placed above the interface at a downward angle so that the interface appeared as a clear boundary between a low-intensity region (the air phase) and a middle or high-intensity region (the liquid phase). An improved intensity threshold method accounting for inhomogeneous lighting was used to detect this edge and subsequent morphological operations yielded an accurate representation of the wave profiles.…”

Section: Introductionmentioning

confidence: 99%

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Dynamic masking of PIV images using the Radon transform in free surface flows

Sanchis

Jensen

2011

Exp Fluids

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Particle image velocimetry (PIV) processing of free surface flow images often requires the use of digital masks to overcome the problems caused by the interface. In cases where a large number of particle images are collected it is essential that the time-varying boundary between the two phases can be tracked automatically to produce the binary masks. The Radon transform-based technique presented in this paper allows the automatic detection of the air-water interface in a stream of particle images acquired from a single camera. It is applied to time-resolved PIV measurements in the liquid phase of a stratified multiphase flow in a circular pipe. Accuracy estimations are provided using synthetic and real wave profiles. An extension to the more complex case of an overturning wave is also discussed.

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Turbulence statistics and flow structure in fluid flow using particle image velocimetry technique: A review

Ayegba

Edomwonyi‐Otu

2020

Engineering Reports

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Particle image velocimetry (PIV) measurement technique provides an excellent opportunity for investigating instantaneous spatial structures which are not always possible with point measurements techniques like laser Doppler velocimetry. In this review, it was shown that PIV technique provides an effective means of visualizing important structures of Newtonian and drag‐reducing fluid flows. Such structures include large‐scale‐events that constitute an important portion of the Reynolds stress tensor; shear layers of drag‐reducing flows, which have been suggested to constitute the mechanism of drag reduction (DR); and near wall vortices/low speed streaks which constitute the mechanism of turbulence production. PIV investigations of turbulence statistics in Newtonian and drag‐reducing fluid flows were reviewed with the view of providing explanation to DR by additives. Results of turbulence statistics, for Newtonian fluid flow, showed that streamwise velocity fluctuations and turbulence intensity had peak values close to the wall, in a region of high mean velocity gradient, while radial fluctuating velocity and Reynolds stress tensor had peaks further from the wall and at approximately the same detachment from the wall. In single‐ and two‐phase flows in horizontal channels, the velocity profile of polymer solution, in the turbulent regime, show asymmetric behavior. This review highlighted important interfacial characteristics in gas‐liquid flows such as S‐shaped velocity profile as well as the turbulences statistics in each phase and across the interface region. Drag‐reducing agents (DRAs)‐imposed changes on turbulence statistics and flow structures were also examined. PIV studies of drag‐reducing flows showed that DRAs act to dampen wall‐normal‐, streamwise fluctuating velocity, and Reynolds stress tensor. The reduction in Reynolds stress tensor is higher than the reduction of both wall‐normal and streamwise velocity fluctuations and this discrepancy has been associated with the decorrelation of the component of fluctuating velocity. Furthermore, the addition of DRA produces a shift of the peak of wall‐normal velocity fluctuations further from the wall due to increased buffer layer thickness. DRAs do not only act to reduce drag but also to modify the flow structure. The major influence of DRAs on flow structures is seen in the reduced strength and population of vortices close to the wall, increased spacing between low‐speed streaks, reduced frequency of large‐scale events and reduced concentration of small eddies. Effect of DRAs on flow structures depends not only on the level of DR but also on the concentration and molecular weight. The effect of concentration is linked to the elastic properties of the DRA. The influence of DRA on oil‐water flows in similar to its effect on single phase water flow with regards to changes in near wall structures and turbulence statistics. A few research gaps and limitations of the PIV techniques were also highlighted.

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A particle-image based wave profile measurement technique

Cited by 15 publications

References 7 publications

PIV measurements of waves and turbulence in stratified horizontal two-phase pipe flow

PIV measurements of waves and turbulence in stratified horizontal two-phase pipe flow

Dynamic masking of PIV images using the Radon transform in free surface flows

Turbulence statistics and flow structure in fluid flow using particle image velocimetry technique: A review

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