Three-dimensional flow measurements on flapping wings using synthetic aperture PIV

Langley, Kenneth R.; Hardester, Eric; Thomson, Scott L.; Truscott, Tadd

doi:10.1007/s00348-014-1831-4

Cited by 20 publications

(15 citation statements)

References 27 publications

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“…Extensive experiments have been carried out in the past to characterize the aerodynamics of natural fliers, such as birds (Spedding et al 2003;Hedenström et al 2006;Johansson and Hedenström 2009;Cheng et al 2016), bats Hubel et al 2010;Muijres et al 2011) and insects (Ellington et al 1996;Srygley and Thomas 2002;Bomphrey et al 2006Bomphrey et al , 2012Fuchiwaki et al 2013;Muijres et al 2014;Langley et al 2014;Henningsson et al 2015). Similar studies have also been reported for flapping-wing MAVs (De Clercq et al 2009;Mazaheri and Ebrahimi 2011;Ren et al 2013), or simplified mechanisms that mimic flapping kinematics, but do not possess the ability to fly independently (Ellington et al 1996;Birch and Dickinson 2001;Lehmann et al 2005;Tarascio et al 2005;Lu and Shen 2008;Ghosh et al 2012;Cheng et al 2014;Langley et al 2014).…”

Section: Introductionmentioning

confidence: 82%

Large-scale volumetric flow visualization of the unsteady wake of a flapping-wing micro air vehicle

et al. 2019

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The objective of this experimental investigation is the volumetric visualization of the near wake topology of the vortex structures generated by a flapping-wing micro air vehicle. To achieve the required visualization domain (which in the present experiments amounts to a size of 60,000 cm 3 ), use is made of robotic particle image velocimetry, which implements coaxial illumination and imaging in combination with the use of helium-filled soap bubbles as tracer particles. Particle trajectories are determined via Lagrangian particle tracking and information of different phases throughout the flapping cycle is obtained by means of a phase-averaging procedure applied to the particle tracks. Experiments have been performed at different settings (flow speed, flapping frequency, and body angle) that are representative of actual flight conditions, and the effect of reduced frequency on the wake topology is investigated. Furthermore, experiments have been carried out in both tethered and freeflight conditions, allowing an unprecedented comparison between the aerodynamics of the two conditions. Graphic abstractElectronic supplementary material The online version of this article (https ://doi.org/10.

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Section: Introductionmentioning

confidence: 82%

Large-scale volumetric flow visualization of the unsteady wake of a flapping-wing micro air vehicle

et al. 2019

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“…The line integral method for circulation is chosen since the method of integration of all vorticity in a set area above a threshold level (e.g., Epps and Techet 2007) is extremely sensitive to the chosen threshold level. Langley et al (2014) show that the circulation magnitude is substantially underestimated at higher threshold levels even though the vorticity threshold level does not influence general temporal trends in vortex circulation as measured in a SAPIV experiment.…”

Section: Velocity Field Reconstruction and Analysismentioning

confidence: 91%

“…SAPIV methods are presented in detail by Belden et al (2010), and applications of SAPIV to flapping wings are presented by Langley et al (2014). SAPIV uses arrays of cameras, each with a different line of sight, to image a scene from multiple viewpoints.…”

Section: Synthetic Aperture Pivmentioning

confidence: 98%

“…Belden et al (2010) and Langley et al (2014) therefore use an additive method, in lieu of a multiplicative algorithm, such that the refocused image on a given focal plane k is where N is the number of cameras, and I FP ki is the transformed image from each camera on the k th focal plane. After refocusing, SAPIV methods typically filter each reconstructed focal plane separately to retain only particles with intensities above a certain threshold, determined by a Gaussian fit to the focal plane intensity distribution.…”

Section: Weighted Refocusingmentioning

confidence: 99%

“…For example, Jeon and Sung (2012) and Im et al (2015) separate particles from an arbitrary background based on the brightness and size in pixels of features in the image, but this segmentation method is strongly dependent on high-intensity contrast between the particles and a much fainter background, and the bright body reflections present in the SAPIV images of the danio could not be similarly separated. Edge detection procedures and morphological operations also can be used to remove objects (e.g., Adhikari and Longmire 2012;Langley et al 2014). These methods do not directly address the issues with bright and dark spots in images as PIV image segmentation methods do.…”

Section: Fish Body Reconstructionmentioning

confidence: 99%

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Quantitative wake analysis of a freely swimming fish using 3D synthetic aperture PIV

Mendelson

Techet

2015

Exp Fluids

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be significantly improved with detailed quantitative analysis of the momentum transfer between the fish and the fluid during swimming behaviors. Fish swimming behavior is inherently three-dimensional (3D), with multifarious fin and body motions and fin-wake interactions. The complexity of these swimming behaviors suggests that 3D rendering, with sufficient spatial and temporal resolution, is necessary to simultaneously capture the relevant kinematics and hydrodynamics to facilitate the quantification of propulsive performance.Early work on fish swimming hydrodynamics employed qualitative shadowgraphy techniques, suggesting a series of linked 3D vortex rings in the wake of a steadily swimming fish, as well as during a "push and coast" swimming mode (McCutchen 1977). Looking to quantify wake hydrodynamics behind swimming fish, researchers turned to noninvasive techniques such as particle image velocimetry (PIV). PIV allows for non-intrusive measurements of the velocity field in a fluid by imaging, and then tracking, the motion of reflective flow tracers over time. Fundamental details on the implementation of algorithms used in PIV can be found in Raffel et al. (1998).PIV measurements taken behind steadily swimming fish along the horizontal mid-plane of the body reveal clear reverse Kármán street vortex configurations in the fish wake (e.g., Stamhuis and Videler 1995;Wolfgang et al. 1999;Müller et al. 2000). Using multiple planes of 2D PIV measurements behind the pectoral fin of a steadily swimming bluegill sunfish, Drucker and Lauder (1999) reconstruct the wake of this fin revealing a series of staggered and interconnected vortex rings. Along the horizontal center plane of these linked vortex rings, the telltale reverse Kármán street of a propulsive thrust wake is present.Abstract Synthetic aperture PIV (SAPIV) is used to quantitatively analyze the wake behind a giant danio (Danio aequipinnatus) swimming freely in a seeded quiescent tank. The experiment is designed with minimal constraints on animal behavior to ensure that natural swimming occurs. The fish exhibits forward swimming and turning behaviors at speeds between 0.9 and 1.5 body lengths/second. Results show clearly isolated and linked vortex rings in the wake structure, as well as the thrust jet coming off of a visual hull reconstruction of the fish body. As a benchmark for quantitative analysis of volumetric PIV data, the vortex circulation and impulse are computed using methods consistent with those applied to planar PIV data. Volumetric momentum analysis frameworks are discussed for linked and asymmetric vortex structures, laying a foundation for further volumetric studies of swimming hydrodynamics with SAPIV. Additionally, a novel weighted refocusing method is presented as an improvement to SAPIV reconstruction.

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Portable tomographic PIV measurements of swimming shelled Antarctic pteropods

2016

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Three-dimensional flow measurements on flapping wings using synthetic aperture PIV

Cited by 20 publications

References 27 publications

Large-scale volumetric flow visualization of the unsteady wake of a flapping-wing micro air vehicle

Large-scale volumetric flow visualization of the unsteady wake of a flapping-wing micro air vehicle

Quantitative wake analysis of a freely swimming fish using 3D synthetic aperture PIV

Portable tomographic PIV measurements of swimming shelled Antarctic pteropods

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