Evaluation of transient turbulent flow fields using digital cinematographic particle image velocimetry

The present study describes an experimental investigation of breaking criteria of deepwater wind waves under strong wind action. In a wind wave flume, waves were generated using different wind speeds and measured at different locations to obtain wave trains of no, intermittent, or frequent breaking. Water particle movement and free surface elevation were measured simultaneously using a PIV system and a wave gauge, respectively. For wind waves, not all the waves measured at a fixed location are breaking waves, and the breaking of a larger wave is not guaranteed. However, the larger the wave height, the larger the probability of breaking. In order to take as many breaking waves as possible for the cases of frequent breaking, we used the waves whose heights were close to the highest one-tenth wave height. The experimental results showed that the geometric or kinematic breaking criteria could not explain the occurrence of breaking of wind waves. On the other hand, the vertical acceleration beneath the wave crest was close to the previously suggested limit value, K0.5g, when frequent breaking of large waves occurred, indicating that the dynamic breaking criterion would be good for discriminating breaking waves under a strong wind action. q

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“…The instantaneous acceleration field was obtained by using the finite differentiation scheme shown in Son and Kihm [28]: …”

Section: Dynamic Breaking Criterionmentioning

confidence: 99%

Experimental investigation of breaking criteria of deepwater wind waves under strong wind action

Mizutani

Suh

et al. 2005

Applied Ocean Research

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“…Hence the random velocity error decayed to e v £ 0.015 m/s at a slide impact velocity v s =2.5 m/s. For comparison Son and Kihm (2001) reported a random displacement error of e Dx =0.04 pixels in a similar application of PIV to surface wave breaking and with the same analysis software (LaVision GmbH, Goettingen, Germany, DaVis PIV package).…”

Section: Measurement Accuracymentioning

confidence: 99%

Landslide generated impulse waves.

Fritz

Hager

Minor

2003

Experiments in Fluids

194

160

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Landslide generated impulse waves were investigated in a two-dimensional physical laboratory model based on the generalized Froude similarity. Digital particle image velocimetry (PIV) was applied to the landslide impact and wave generation. Areas of interest up to 0.8 m by 0.8 m were investigated. The challenges posed to the measurement system in an extremely unsteady threephase flow consisting of granular matter, air, and water were considered. The complex flow phenomena in the first stage of impulse wave initiation are: high-speed granular slide impact, slide deformation and penetration into the fluid, flow separation, hydrodynamic impact crater formation, and wave generation. During this first stage the three phases are separated along sharp interfaces changing significantly within time and space. Digital masking techniques are applied to distinguish between phases thereafter allowing phase separated image processing. PIV provided instantaneous velocity vector fields in a large area of interest and gave insight into the kinematics of the wave generation process. Differential estimates such as vorticity, divergence, elongational, and shear strain were extracted from the velocity vector fields. The fundamental assumption of irrotational flow in the Laplace equation was confirmed experimentally for these non-linear waves. Applicability of PIV at large scale as well as to flows with large velocity gradients is highlighted.

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“…The vorticity components X x , X y and X z are evaluated with the formulae based on Stokes' theorem (Son and Kihm 2001;Foucaut and Stanislas 2002).…”

Section: Piv Measurementsmentioning

confidence: 99%

Thermo-fluid-dynamic analysis of the flow in a rotating channel with a sharp “U” turn

2012

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Infrared thermography has been employed to carry out a detailed convective heat transfer measurements at Re = 20,000 in a two-pass square channel both for the static case (absence of channel rotation) and for the rotating case (Ro = 0.3). At the same time, the main and secondary flow fields have been measured by means of particle image velocimetry with the aim to investigate how the flow behavior affects the local distributions of the convective heat transfer coefficient for the two cases. The normal-towall velocity component (w) and the turbulent kinetic energy, both measured close to the heat exchanging wall, have been used to formulate an empirical heat transfer correlation within an attempt to identify the role performed by these two quantities on the convective heat transfer coefficient distributions. The latter ones have been reported in terms of normalized Nusselt number (Nu/Nu*) maps, where Nu* is the Nusselt number evaluated with the classical Dittus-Bölter correlation.

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Evaluation of transient turbulent flow fields using digital cinematographic particle image velocimetry

Cited by 13 publications

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Experimental investigation of breaking criteria of deepwater wind waves under strong wind action

Experimental investigation of breaking criteria of deepwater wind waves under strong wind action

Landslide generated impulse waves.

Thermo-fluid-dynamic analysis of the flow in a rotating channel with a sharp “U” turn

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