Tomographic particle image velocimetry

Elsinga, Gerrit E.; Scarano, Fulvio; Wieneke, Bernhard; Oudheusden, B.W. van

doi:10.1007/s00348-006-0212-z

Cited by 1,004 publications

(765 citation statements)

References 22 publications

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“…Tomographic PIV (Elsinga et al 2006) was selected to measure the instantaneous distribution of the velocity vector and the velocity gradient tensor in the three-dimensional domain of interest. The flow was seeded homogeneously by water-glycol droplets of average diameter of 1µm.…”

Section: Tomographic Pivmentioning

confidence: 99%

Three-dimensional organisation of primary and secondary crossflow instability

2016

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An experimental investigation of primary and secondary crossflow instability developing in the boundary layer of a 45 • swept wing, at a chord Reynolds number of 2.17·10 6 is presented. Linear stability theory is applied for preliminary estimation of the flow stability while surface flow visualisation using fluorescent oil is employed to inspect the topological features of the transition region. Hot-wire anemometry is extensively used for the investigation of the developing boundary layer and identification of the statistical and spectral characteristics of the instability modes. Primary stationary as well as unsteady type-I (z-mode), type-II (y-mode) and type-III modes are detected and quantified. Finally, three-component, three-dimensional measurements of the transitional boundary layer are performed using tomographic particle image velocimetry. This research presents the first application of an optical experimental technique for this type of flow. Among the optical techniques tomographic velocimetry represents, to date, the most advanced approach allowing the investigation of spatially correlated flow structures in threedimensional fields. Proper orthogonal decomposition (POD) analysis of the captured flow fields is applied to this goal. The first POD mode features a newly reported structure related to low-frequency oscillatory motion of the stationary vortices along the spanwise direction. The cause of this phenomenon is only conjectured. Its effect on transition is considered negligible but, given the related high energy level, it needs to be accounted for in experimental investigations. Secondary instability mechanisms are captured as well. The type-III mode corresponds to low frequency primary travelling crossflow waves interacting with the stationary ones. It appears in the inner upwelling region of the stationary crossflow vortices and is characterised by elongated structures approximately aligned with the axis of the stationary waves. The type-I secondary instability consists instead of significantly inclined structures located at the outer upwelling region of the stationary vortices. The much narrower wavelength and higher advection velocity of these structures correlate with the higher-frequency content of this mode. The results of the investigation of both primary and secondary instability from the exploited techniques agree with and complement each other and are in line with existing literature. Finally, they present the first experimental observation of the secondary instability structures under natural flow conditions.

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Section: Tomographic Pivmentioning

confidence: 99%

Three-dimensional organisation of primary and secondary crossflow instability

2016

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“…[1][2][3][4] Earlier methods, based on holographic reconstruction 5,6 required much more elaborate optical setups. Another method, scanning stereoscopic PIV, 7,8 is simpler to establish, but its application is limited to low speed flows.…”

Section: A Volumetric Measurements Of Velocitymentioning

confidence: 99%

Scanning tomographic particle image velocimetry applied to a turbulent jet

2013

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We introduce a modified tomographic PIV technique using four high-speed video cameras and a scanning pulsed laser-volume. By rapidly illuminating adjacent subvolumes onto separate video frames, we can resolve a larger total volume of velocity vectors, while retaining good spatial resolution. We demonstrate this technique by performing time-resolved measurements of the turbulent structure of a round jet, using up to 9 adjacent volume slices. In essence this technique resolves more velocity planes in the depth direction by maintaining optimal particle image density and limiting the number of ghost particles. The total measurement volumes contain between 1 ×106 and 3 ×106 velocity vectors calculated from up to 1500 reconstructed depthwise image planes, showing time-resolved evolution of the large-scale vortical structures for a turbulent jet of Re up to 10 000.

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“…The velocity field is then calculated by either a volumetric cross-correlation or a volumetric tracking algorithm as opposed to stereoscopic approaches, where the third component is reconstructed by the in-plane velocity. At least four different views are required for a reconstruction with sufficient quality for most applications (Elsinga et al 2006). The reconstruction of the volumetric intensity field is a mathematically ill-posed problem and iterative algorithms have to be used.…”

Section: Tomographic Imagingmentioning

confidence: 99%

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

Cierpka

Kähler

2011

J Vis

131

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The reliable measurement of the 3D3C velocity field in microfluidic devices becomes more and more important for future optimization and developments for lab-on-a-chip applications or point-of-care medical diagnosis systems. In the past years, different particle-based imaging methods, such as confocal scanning microscopy, holography, stereoscopic and tomographic imaging or approaches based on defocused particle images or optical aberrations have been developed and applied successfully to measure velocity fields in microfluidic systems. The benefits and drawbacks of these methods will be discussed in detail as the proper understanding of the measurement principle is essential to select the most appropriate technique for a desired measurement application. Once an imaging method is chosen, the velocity can be estimated by correlation-based methods or tracking approaches. The advantages and disadvantages of both methods and the importance of image preprocessing will also be discussed in detail.

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Tomographic particle image velocimetry

Cited by 1,004 publications

References 22 publications

Three-dimensional organisation of primary and secondary crossflow instability

Three-dimensional organisation of primary and secondary crossflow instability

Scanning tomographic particle image velocimetry applied to a turbulent jet

Particle imaging techniques for volumetric three-component (3D3C) velocity measurements in microfluidics

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