PIV Measurements of Oscillatory Flow Over a Rippled Bed.

Earnshaw, H. C.; Bruce, T.; Greated, C. A.; Easson, W. J.

doi:10.1061/9780784400890.143

Cited by 6 publications

(6 citation statements)

References 2 publications

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“…From linear diffraction analysis the y-z water velocity RAO are determined. They are plotted together with the results from the PIV analysis in figure (5) to figure (8). As can be seen from the calculated and measured water velocity RAOs an definite over estimation from the linear computations is observed as expected.…”

Section: Discussion Of Results Flow Images Near Bilges Of Fpso Modelsupporting

confidence: 59%

“…Earlier attempts to use PIV techniques for offshore applications have been reported by Tukker et al [4]. Applications of detail spatial velocity measurements in civil engineering and offshore engineering applications have been reported by Gray et al ( [5], [6], [7]), Earnshaw et al ( [8], [9]) and Jensen et al ( [10], [11]). The linear diffraction computations used in this study are partly based on the work presented by van Oortmerssen [12] and Huijsmans [13] and partly using WAMIT software.…”

Section: Introductionmentioning

confidence: 99%

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The Flow Around FPSO’s in Steep Regular Beam Waves: Results of PIV Experiments and RANS Computations

Huijsmans

Graham

Kendon

2005

24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 3

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This paper investigates the hydrodynamical aspects of a fixed FPSO in regular waves. The emphasis is geared to the validation of state of the art CFD techniques, using particle image velocimetry measurements on the water velocities around a captive model of an FPSO in regular waves. The main focus is on the following issues: Determination of the water velocities around the vessel using PIV techniques and pressures on a girth below and just above the mean waterline of the vessel using pressure gauges. Comparison of the detailed RANS simulations of the flow around the bilges of the FPSO. The resulting pressure profiles along the girth, especially near the waterline, showed a significant non-linear effect in steep beam wave conditions. The velocities as measured near the bilges of the vessel indicated a strong separation at the bilges of the vessel. This leads to an overestimation of the water velocities near the bilges of the vessel as calculated using a linear diffraction programme. The resulting pressure profiles along the girth, especially near the waterline, showed a significant non-linear effect in steep beam wave conditions. The velocities as measured near the bilges of the vessel indicated a strong separation at the bilges of the vessel. This leads to an overestimation of the water velocities near the bilges of the vessel as calculated using a linear diffraction programme. RANS simulations will give a more realistic flow profile around the bilges.

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Section: Discussion Of Results Flow Images Near Bilges Of Fpso Modelsupporting

confidence: 59%

Section: Introductionmentioning

confidence: 99%

The Flow Around FPSO’s in Steep Regular Beam Waves: Results of PIV Experiments and RANS Computations

Huijsmans

Graham

Kendon

2005

24th International Conference on Offshore Mechanics and Arctic Engineering: Volume 3

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“…This strong correlation was also noticed by Ribberink and Al-Salem (1994) on the basis of their own data and other, small-scale flow tunnel data. Earnshaw et al (1994) performed particle image velocimetry measurements of the instantaneous velocity patterns above solid ripples for four different flow conditions in a towing tank and in a small-scale wave flume and found that the maximum radius of the vortices was about one ripple height. At or just before flow reversal, the vortices are shed and lifted to a height of about 1.5η which seems to be independent of the flow condition.…”

Section: Model Improvementmentioning

confidence: 99%

Sand Transport Over Rippled Beds in Oscillatory Flow

Werf¹,

Ribberink²

2007

Coastal Engineering 2006

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Sand Transport over Rippled Beds in Oscillatory Flow PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit Twente, op gezag van de rector magnificus, prof. dr. W.H.M. Zijm, volgens besluit van het College voor Promoties in het openbaar te verdedigen op vrijdag 19 mei 2006 om 15.00 uur door Jebbe Jacob van der Werf geboren op 31 oktober 1979 te Zwolle Dit proefschrift is goedgekeurd door:

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“…Comparisons with near‐bottom‐mounted current meters have shown high correlations, but these were restricted to mean flows rather than instantaneous motions. Video‐based methods have also included the use of particle image velocimetry (PIV) which has been used to investigate the vertical flow structure under breaking and nonbreaking waves [ Gray and Greated , 1988; She et al , 1997; Chang and Liu , 1998] and the fluid motion over a rippled bed [ Earnshaw et al , 1994]. More recently, PIV has been used to extract instantaneous surface current velocities in the swash zone of a high energy beach [ Puleo and Holland , 2000; Holland et al , 2001].…”

Section: Introductionmentioning

confidence: 99%

Comparison of optical and radar measurements of surf and swash zone velocity fields

et al. 2003

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[1] Surf zone bore celerities and swash zone surface currents were measured on a shallow sloping, low-energy beach using two remote sensing methods that differ fundamentally in their imaging mechanisms. Microwave Doppler radar measures electromagnetic backscatter from small-scale ocean surface roughness while video-based particle image velocimetry (PIV) relies on image texture resulting from variations in light reflectivity from the ocean surface. Imagery from the two methods showed high correlation, in which regions of high radar backscatter corresponded to visibly identifiable waves and bores propagating across the surf zone. Correlation coefficients between radial velocity time series sampled using the two methods at multiple locations across the surf zone were typically greater than 0.5 for frequencies less than a noise cutoff of 0.25 Hz. Similarly, spectra were found to be coherent at the 95% level with a nearly zero phase shift between the two signals near the broad spectral peak between 0.02 and 0.25 Hz. However, some significant differences were evident. PIV was capable of estimating both cross-shore and alongshore surface velocities while the use of one microwave Doppler radar system restricted surface velocity estimates from that technique to line of sight (radial) only. PIV was found to be more capable of estimating swash zone (uprush and backwash) surface velocities as a smoother water surface in the swash zone adversely affected radar reflectivity. In contrast, microwave Doppler radar was found to be more capable of estimating the surface velocity between bores when insufficient image texture was recorded in the video imagery. Both techniques were capable of measuring surf zone bore celerities through comparison to a shallow water model and to independent celerity estimates extracted from the slope of individual bore trajectories. Typical normalized errors were roughly 25% for radar and 15% for PIV.

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PIV Measurements of Oscillatory Flow Over a Rippled Bed.

Cited by 6 publications

References 2 publications

The Flow Around FPSO’s in Steep Regular Beam Waves: Results of PIV Experiments and RANS Computations

The Flow Around FPSO’s in Steep Regular Beam Waves: Results of PIV Experiments and RANS Computations

Sand Transport Over Rippled Beds in Oscillatory Flow

Comparison of optical and radar measurements of surf and swash zone velocity fields

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