Pulsed laser technique application to liquid and gaseous flows and the scattering power of seed materials

Adrian, Ronald J.; Yao, Chung-Sheng

doi:10.1364/ao.24.000044

Cited by 249 publications

(131 citation statements)

References 8 publications

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“…With a digital resolution of 65.4 px/mm corresponding to a magnification of 0.47 and a diaphragm aperture of 8, the imaged particle on the sensor is about 2.3 pixel. 41 This setting guarantees absence of peak-locking effects in the measurements. The absence of peak locking was a posteriori verified by plotting the histogram of the round-off of the correlated vector displacements with their integer values.…”

Section: Fig 2 Measurement Domains For the Planar (Left) And Tomogrmentioning

confidence: 99%

Three-dimensional flow field over a trailing-edge serration and implications on broadband noise

2016

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The three-dimensional flow field over the suction side of a NACA 0018 airfoil with trailing-edge serrations was studied by means of time-resolved tomographic particle image velocimetry. Mean flow results show that the boundary layer thickness decreases along the streamwise direction with a corresponding reduction of the size of the turbulent structures developing over the suction side of the serrations. At a positive angle of attack, streamwise-oriented and counter-rotating vortices aligned with the edge of the serrations are found to be the main features of the mean flow field. Their formation is attributed to the pressure imbalance between the two sides of the airfoil and the mixing layer at the edge. They locally modify the effective angle seen by the turbulent flow approaching the serrated edge. This effect may contribute to the serration underperformance in terms of noise reduction reported in literature. The spatial distribution of the spectra of the source term of the Poisson equation, which relates the velocity field to pressure fluctuations, suggests that the contribution of the serrations to far-field broadband noise is a function of the streamwise location. This observation is congruent with the spectra of the wall-normal and spanwise velocity fluctuations, which typically show low intensity close to the tips of the individual serrations. It follows that analytical models must take into account the local contribution to the far-field noise induced by the streamwise variation of the hydrodynamic pressure on the serration surface.

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Section: Fig 2 Measurement Domains For the Planar (Left) And Tomogrmentioning

confidence: 99%

Three-dimensional flow field over a trailing-edge serration and implications on broadband noise

2016

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“…As a result, no velocity measurements can be obtained in the region with fewer to no particle tracers (1st international PIV challenge, Stanislas et al 2003;Bhagwat and Ramasamy 2012). The use of even smaller particles can mitigate the problem of the radial drift; however, the amount of light scattered rapidly decays by decreasing the particle diameter (Adrian and Yao 1985;Lecuona et al 2002).…”

Section: Introductionmentioning

confidence: 99%

Helium-filled soap bubbles for vortex core velocimetry

2017

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“…DPIV is a video-based flow measurement technique first introduced and named by Willert and Gharib (Willert and Gharib, 1991). It is a variant of the film-based technique, particle image velocimetry (PIV) or pulsed laser velocimetry, developed a decade earlier (Adrian, 1984;Adrian and Yao, 1985). The basic concept of DPIV is that images of very small, neutrally buoyant particles that are small enough to follow fluid motions, but large enough to be imaged by the camera, are statistically tracked from one video frame to the next (Willert and Gharib, 1991).…”

Section: Introductionmentioning

confidence: 99%

Measurement of hydrodynamic force generation by swimming dolphins using bubble DPIV

Fish

Legac

Williams

et al. 2014

Journal of Experimental Biology

111

101

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Attempts to measure the propulsive forces produced by swimming dolphins have been limited. Previous uses of computational hydrodynamic models and gliding experiments have provided estimates of thrust production by dolphins, but these were indirect tests that relied on various assumptions. The thrust produced by two actively swimming bottlenose dolphins (Tursiops truncatus) was directly measured using digital particle image velocimetry (DPIV). For dolphins swimming in a large outdoor pool, the DPIV method used illuminated microbubbles that were generated in a narrow sheet from a finely porous hose and a compressed air source. The movement of the bubbles was tracked with a high-speed video camera. Dolphins swam at speeds of 0.7 to 3.4 m s −1 within the bubble sheet oriented along the midsagittal plane of the animal. The wake of the dolphin was visualized as the microbubbles were displaced because of the action of the propulsive flukes and jet flow. The oscillations of the dolphin flukes were shown to generate strong vortices in the wake. Thrust production was measured from the vortex strength through the Kutta-Joukowski theorem of aerodynamics. The dolphins generated up to 700 N during small amplitude swimming and up to 1468 N during large amplitude starts. The results of this study demonstrated that bubble DPIV can be used effectively to measure the thrust produced by large-bodied dolphins.

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Pulsed laser technique application to liquid and gaseous flows and the scattering power of seed materials

Cited by 249 publications

References 8 publications

Three-dimensional flow field over a trailing-edge serration and implications on broadband noise

Three-dimensional flow field over a trailing-edge serration and implications on broadband noise

Helium-filled soap bubbles for vortex core velocimetry

Measurement of hydrodynamic force generation by swimming dolphins using bubble DPIV

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