Long-Duration Time-Resolved PIV to Study Unsteady Aerodynamics

Taylor, Zachary; Gurka, Roi; Kopp, Gregory A.; Liberzon, Alex

doi:10.1109/tim.2010.2047149

Cited by 180 publications

(117 citation statements)

References 18 publications

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“…A long-duration time-resolved PIV system [42] was employed for the wake flow measurements. The PIV system consisted of a 80 W double-head diode-pumped Q-switched Nd : YLF laser at a wavelength of 527 nm and two CMOS cameras (Photron FASTCAM-1024PCI) with spatial resolution of 1024 Â 1024 pixel 2 operating at a rate of 1000 Hz.…”

Section: Particle Image Velocimetrymentioning

confidence: 99%

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Flow pattern similarities in the near wake of three bird species suggest a common role for unsteady aerodynamic effects in lift generation

et al. 2017

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Analysis of the aerodynamics of flapping wings has yielded a general understanding of how birds generate lift and thrust during flight. However, the role of unsteady aerodynamics in avian flight due to the flapping motion still holds open questions in respect to performance and efficiency. We studied the flight of three distinctive bird species: western sandpiper ( Calidris mauri ), European starling ( Sturnus vulgaris ) and American robin ( Turdus migratorius ) using long-duration, time-resolved particle image velocimetry, to better characterize and advance our understanding of how birds use unsteady flow features to enhance their aerodynamic performances during flapping flight. We show that during transitions between downstroke and upstroke phases of the wing cycle, the near wake-flow structures vary and generate unique sets of vortices. These structures appear as quadruple layers of concentrated vorticity aligned at an angle with respect to the horizon (named ‘double branch’). They occur where the circulation gradient changes sign, which implies that the forces exerted by the flapping wings of birds are modified during the transition phases. The flow patterns are similar in (non-dimensional) size and magnitude for the different birds suggesting that there are common mechanisms operating during flapping flight across species. These flow patterns occur at the same phase where drag reduction of about 5% per cycle and lift enhancement were observed in our prior studies. We propose that these flow structures should be considered in wake flow models that seek to account for the contribution of unsteady flow to lift and drag.

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Section: Particle Image Velocimetrymentioning

confidence: 99%

“…The PIV FOV for the robin data was 14 Â 14 cm 2 (1.4c Â 1.4c). The velocity fields were computed using OpenPIV [42] with 32 Â 32 pixel 2 interrogation windows and 50% overlap, yielding a spatial resolution of 32 vectors per average chord, equal to 1.8 vectors mm…”

Section: Particle Image Velocimetrymentioning

confidence: 99%

Flow pattern similarities in the near wake of three bird species suggest a common role for unsteady aerodynamic effects in lift generation

et al. 2017

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“…Videos were analyzed using a custom-written MATLAB routine that cross-correlated regions in the videos between successive frames using code from the openPIV software package (Taylor et al, 2010). For each position of the illuminated plane, a flow field was generated by analyzing data from 150 frames of video.…”

Section: Flow Analysismentioning

confidence: 99%

Movements ofRana catesbeianatadpoles in weak current flows resemble a directed random walk

Schmidt

Knowles

Simmons

2011

Journal of Experimental Biology

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SUMMARYCurrent flow is an important biological stimulus for larval anuran amphibians, but little is known about how it is perceived. We quantified behavioral responses to controlled water flow in the bullfrog tadpole (Rana catesbeiana) at developmental stages prior to metamorphic climax, and examined the contribution of a functioning lateral line system to these behaviors. Tadpoles at these developmental stages show a significant preference for the sides and bottom of a flow tank. In response to water flow at three different rates, they exhibit a significant, time-dependent tendency to move downstream, away from the source of the flow, and to remain in areas where flow is minimized. The consistency of these behaviors at all tested flow rates suggests that the animals are not simply passively pushed by the current; instead, they actively swim away from the current source. Tadpoles do not exhibit positive rheotaxis towards the source of the flow at any flow rate but as a group are randomly oriented. Treatment with cobalt chloride, a known blocker of superficial neuromast function, significantly reduces the tendency to move downstream, but does not alter the preference for the sides and bottom of the tank. Tadpoles' movements under flow are consistent with a model of locomotion based on a directed random walk.

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“…1b. Most freely available PIV-DIC software used for geotechnical analyses use some form of cross-correlation to obtain integer pixel displacements followed by subpixel interpolation of the correlation peak (e.g., GeoPIV (White et al 2003), MatPIV (Sveen and Cowen 2004), PIVlab (Thielicke and Stamhuis 2014), and OpenPIV (Taylor et al 2010)). In these algorithms the subsets (or patches) are generally not allowed to deform (so-called zero-order deformation).…”

Section: Introductionmentioning

confidence: 99%

Improved image-based deformation measurement for geotechnical applications

et al. 2016

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This paper describes and benchmarks a new implementation of image-based deformation measurement for geotechnical applications. The updated approach combines a range of advances in image analysis algorithms and techniques best suited to geotechnical applications. Performance benchmarking of the new approach has used a series of artificial images subjected to prescribed spatially varying displacement fields. An improvement by at least a factor of 10 in measurement precision is achieved relative to the most commonly used particle image velocimetry (PIV) approach for all deformation modes, including rigid-body displacements, rotations, and strains (compressive and shear). Lastly, an example analysis of a centrifuge model test is used to demonstrate the capabilities of the new approach. The strain field generated by penetration of a flat footing and an entrapped sand plug into an underlying clay layer is computed and compared for both the current and updated algorithms. This analysis demonstrates that the enhanced measurement precision improves the clarity of the interpretation.Key words: image analysis, model tests, particle image velocimetry, digital image correlation.

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Long-Duration Time-Resolved PIV to Study Unsteady Aerodynamics

Cited by 180 publications

References 18 publications

Flow pattern similarities in the near wake of three bird species suggest a common role for unsteady aerodynamic effects in lift generation

Flow pattern similarities in the near wake of three bird species suggest a common role for unsteady aerodynamic effects in lift generation

Movements ofRana catesbeianatadpoles in weak current flows resemble a directed random walk

Improved image-based deformation measurement for geotechnical applications

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