507 research outputs found
Void fraction measurements and scale effects in breaking waves in freshwater and seawater
No full textThis paper follows from the work of Blenkinsopp and Chaplin (2007) and describes detailed measurements of the time-varying distribution of void fractions generated by breaking waves in freshwater, artificial seawater and natural seawater under laboratory conditions, along with flow visualisation of the entrainment process. The measurements were made with highly sensitive optical fibre phase detection probes and the results demonstrate that although an additional population of fine (d < 0.3 mm) bubbles existed in the seawater cases, the total volume and distribution of entrained air, and the spatial and temporal evolution of the bubble plumes were very similar in all three water types. The influence of water type may be relatively insignificant, but a numerical bubble tracking model shows that the effect of scale is an important consideration when modelling the post-entrainment evolution of breaker-entrained bubble plumes. Consequently the results suggest that while the use of freshwater in laboratory models of oceanic processes can be considered valid in most situations, the effect of scale may impact interpretation of the results
Mass transport around a horizontal cylinder beneath waves
No full textAround a horizontal cylinder submerged beneath waves with its axis parallel to the wave crests there exists, owing to streaming flow in the boundary layer, circulation with the same sense of rotation as that of the orbital motion in the waves. Experimental results, for conditions in which the effects of separation are not important, confirm theoretical predictions of the mass-transport velocity at the outer edge of the oscillatory boundary layer. Pressure measurements on the cylinder reveal a nonlinear component which is interpreted as a consequence of circulation induced by steady streaming.<br/
History forces on a cylinder resulting from an impulsive change in the direction of the incident flow
No full textComputation of non-linear wave reflections and transmissions from a submerged horizontal cylinder
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Non-linear wave interactions with a submerged horizontal cylinder
No full textMeasurements of some non-linear features of waves propagating over a submerged horizontal cylinder with its axis parallel with the wave crests are compared with previous analytical and numerical predictions of the potential flow. Good agreement is found in most respects with second order results for the transmitted waves and the set down in the mean surface level over the cylinder, but a non-linear contribution to the phase lag of the first harmonic wave component is attributed to the effect of circulation around the cylinder induced by viscosity. The limiting conditions at which waves first break over the cylinder are plotted over a wide range of conditions
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