Volumetric velocity measurements of vortex rings from inclined exits

Troolin, Dan; Longmire, Ellen

doi:10.1007/s00348-009-0745-z

Cited by 53 publications

(33 citation statements)

References 14 publications

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“…A 14×14×10 cm region of the test section was illuminated with two pulsed Nd:YAG lasers (LABest, Optronics, China), and paired DDPTV images (Δt=0.5-2.0 ms) of the flow around the squid were captured at 7 Hz. Identification of 3D particle locations and calculation of particle displacements were performed using INSIGHT 4G V3V software (TSI, Inc.), following protocols described in Pereira et al (2000) and Troolin and Longmire (2010). On average, 100,000 particles were identified in each image with triplet yields (matches of particles among the three cameras in the probe) of ∼50,000-60,000 (∼50-60%).…”

Section: Methodsmentioning

confidence: 99%

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Volumetric flow imaging reveals the importance of vortex ring formation in squid swimming tail-first and arms-first

Bartol

Krueger

Jastrebsky

et al. 2015

Journal of Experimental Biology

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Squids use a pulsed jet and fin movements to swim both arms-first (forward) and tail-first (backward). Given the complexity of the squid multi-propulsor system, 3D velocimetry techniques are required for the comprehensive study of wake dynamics. Defocusing digital particle tracking velocimetry, a volumetric velocimetry technique, and high-speed videography were used to study arms-first and tail-first swimming of brief squid Lolliguncula brevis over a broad range of speeds [0-10 dorsal mantle lengths (DML) s] in a swim tunnel. Although there was considerable complexity in the wakes of these multi-propulsor swimmers, 3D vortex rings and their derivatives were prominent reoccurring features during both tail-first and arms-first swimming, with the greatest jet and fin flow complexity occurring at intermediate speeds (1.5-3.0 DML s −1). The jet generally produced the majority of thrust during rectilinear swimming, increasing in relative importance with speed, and the fins provided no thrust at speeds >4.5 DML s ) to counteract negative buoyancy. Propulsive efficiency (η) increased with speed irrespective of swimming orientation, and η for swimming sequences with clear isolated jet vortex rings was significantly greater (η=78.6±7.6%, mean±s.d.) than that for swimming sequences with clear elongated regions of concentrated jet vorticity (η=67.9±19.2%). This study reveals the complexity of 3D vortex wake flows produced by nekton with hydrodynamically distinct propulsors.

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Section: Methodsmentioning

confidence: 99%

“…A voxel size of 8 mm, percentage overlap of 95% and smoothing factor of 1.5 were used in these experiments. A more detailed description of the DDPTV or V3V procedure may be found in Couch and Krueger (2011), Troolin and Longmire (2010) and Flammang et al (2011a,b), with sensitivity analyses performed by Graff and Gharib (2008).…”

Section: Methodsmentioning

confidence: 99%

Volumetric flow imaging reveals the importance of vortex ring formation in squid swimming tail-first and arms-first

Bartol

Krueger

Jastrebsky

et al. 2015

Journal of Experimental Biology

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“…Using an instantaneous volumetric PIV system [21,24,25], we were able to capture series of complete three-dimensional snapshots of the wake structure produced by the heterocercal tails of freely swimming sharks. Four live sharks (mean total length ¼ 24.6 cm), two each of two species, spiny dogfish (Squalus acanthias; see electronic supplementary material) and chain dogfish (Scyliorhinus retifer) with trailing edge spans of 5 -6.5 cm and tail beat amplitudes of 6.5-7.5 cm swam at 0.5, 0.75 and 1.0 body lengths per second in a recirculating flow tank equipped with a volumetric PIV system that captured volumes of 14 Â 14 Â 10 cm 3 (x, y, z) at 7.25 Hz (TSI Inc., Shoreview, MN, USA).…”

Section: Methodsmentioning

confidence: 99%

“…The flow tank was seeded with 50 mm plastic particles that were suspended in flow. Particle position and displacements were calculated between laser pulses using V3V software as detailed in Troolin & Longmire [21] and Pereira et al [25]. In brief, the three lens and charge-coupled device (CCD) arrays (2048 Â 2048) were calibrated by traversing a known target across the transverse (Z) plane of the flow tank where the fish were to swim.…”

Section: Methodsmentioning

confidence: 99%

Volumetric imaging of shark tail hydrodynamics reveals a three-dimensional dual-ring vortex wake structure

et al. 2011

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Understanding how moving organisms generate locomotor forces is fundamental to the analysis of aerodynamic and hydrodynamic flow patterns that are generated during body and appendage oscillation. In the past, this has been accomplished using two-dimensional planar techniques that require reconstruction of three-dimensional flow patterns. We have applied a new, fully three-dimensional, volumetric imaging technique that allows instantaneous capture of wake flow patterns, to a classic problem in functional vertebrate biology: the function of the asymmetrical (heterocercal) tail of swimming sharks to capture the vorticity field within the volume swept by the tail. These data were used to test a previous three-dimensional reconstruction of the shark vortex wake estimated from two-dimensional flow analyses, and show that the volumetric approach reveals a different vortex wake not previously reconstructed from two-dimensional slices. The hydrodynamic wake consists of one set of dual-linked vortex rings produced per half tail beat. In addition, we use a simple passive shark-tail model under robotic control to show that the three-dimensional wake flows of the robotic tail differ from the active tail motion of a live shark, suggesting that active control of kinematics and tail stiffness plays a substantial role in the production of wake vortical patterns.

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“…In order to analyse the three-dimensional dynamics of vortex rings such as the oval vortex ring and AR4 elliptical vortex ring considered in this study, three-dimensional velocimetry is required. The three-dimensional, threecomponent defocusing digital particle image velocimetry (DDPIV) technique (Willert & Gharib 1992;Pereira & Gharib 2002;Pereira et al 2006) has been applied successfully to non-axisymmetric vortex ring flows by Troolin & Longmire (2009) and Kim & Gharib (2011), and is a promising candidate for performing three-dimensional velocimetry measurements on vortex rigs undergoing large deformations.…”

Section: O'farrell and J O Dabirimentioning

confidence: 99%

Pinch-off of non-axisymmetric vortex rings

O’Farrell

Dabiri

2014

J. Fluid Mech.

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The formation and pinch-off of non-axisymmetric vortex rings is considered experimentally. Vortex rings are generated using a non-circular piston-cylinder arrangement, and the resulting velocity fields are measured using digital particle image velocimetry. Three different nozzle geometries are considered: an elliptical nozzle with an aspect ratio of two, an elliptical nozzle with an aspect ratio of four and an oval nozzle constructed from tangent circular arcs. The formation of vortices from the three nozzles is analysed by means of the vorticity and circulation, as well as by investigation of the Lagrangian coherent structures in the flow. The results indicate that, in all three nozzles, the maximum circulation the vortex can attain is determined by the equivalent diameter of the nozzle: the diameter of a circular nozzle of identical cross-sectional area. In addition, the time at which the vortex rings pinch off is found to be constant along the nozzle contours, and independent of relative variations in the local curvature. A formation number for this class of vortex rings is defined based on the equivalent diameter of the nozzle, and the formation number for vortex rings of the three geometries considered is found to lie in the range of 3-4. The implications of the relative shape and local curvature independence of the formation number on the study and modelling of naturally occurring vortex rings such as those that appear in biological flows is discussed.

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Volumetric velocity measurements of vortex rings from inclined exits

Cited by 53 publications

References 14 publications

Volumetric flow imaging reveals the importance of vortex ring formation in squid swimming tail-first and arms-first

Volumetric flow imaging reveals the importance of vortex ring formation in squid swimming tail-first and arms-first

Volumetric imaging of shark tail hydrodynamics reveals a three-dimensional dual-ring vortex wake structure

Pinch-off of non-axisymmetric vortex rings

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