Energy Dissipation and Air Bubbles Mixing Inside Surf Zone

Hwung, Hwung Hweng; Chyan, Jih Ming; Chung, Yeong Chyang

doi:10.1061/9780872629332.023

Cited by 15 publications

(27 citation statements)

References 3 publications

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“…The temporal variation of void fraction above the still water normalized by the wave period and average void fraction appears to be remarkably self-similar (independently of the breaker type). Hwung et al (1992) found a deeper penetration of air bubbles under plunging breaking waves and higher void fractions (18%), compared to the spilling breaking waves (12%). Similarly Hoque and Aoki (2005), using a conductivity probe, measured maximum void fractions of 20% and 16% beneath plunging and spilling breakers, respectively.…”

Section: Flow Analogies or Not?mentioning

confidence: 98%

Are breaking waves, bores, surges and jumps the same flow?

Lubin

Chanson

2016

Environ Fluid Mech

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The flow structure in the aerated region of the roller generated by breaking waves remains a great challenge to study, with large quantities of entrained air and turbulence interactions making it very difficult to investigate in details. A number of analogies were proposed between breaking waves in deep or shallow water, tidal bores and hydraulic jumps. Many numerical models used to simulate waves in the surf zone do not implicitly simulate the breaking process of the waves, but are required to parameterise the wave-breaking effects, thus relying on experimental data. Analogies are also assumed to quantify the roller dynamics and the energy dissipation. The scope of this paper is to review the different analogies proposed in the literature and to discuss current practices. A thorough survey is offered and a discussion is developed an aimed at improving the use of possible breaking proxies. The most recent data are revisited and scrutinised for the use of most advanced numerical models to educe the surf zone hydrodynamics. In particular, the roller dynamics and geometrical characteristics are discussed. An open discussion is proposed to explore the actual practices and propose perspectives based on the most appropriate analogy, namely the tidal bore.

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Section: Flow Analogies or Not?mentioning

confidence: 98%

Are breaking waves, bores, surges and jumps the same flow?

Lubin

Chanson

2016

Environ Fluid Mech

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“…A bore is a body of highly turbulent and aerated water moving shoreward. Energy is dissipated by the entrainment of air (Ftihrboter 1970, Hwung et al 1992. As with breaking waves, prediction of pressures exerted by broken waves relies on experimental and empirical evidence.…”

Section: Erosion By Wavesmentioning

confidence: 99%

Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand

2000

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Shore platforms on the Kaikoura Peninsula have been examined to determine the roles of marine and subaerial weathering processes in platform evolution. Erosion was measured to assess rates of development and processes of erosion. Lowering rates on platforms are presented from two years of monitoring using a traversing micro-erosion meter. Cliff retreats were calculated using aerial photographic interpretation. Marine processes were investigated by using deep water wave data, by measuring waves on shore platforms and by analysing measured tidal data. Weathering processes were investigated using tidal data, climate data, the Schmidt Hammer test, and a laboratory experiment on wetting and drying.Lowering rates over two years ranged from 0.07 to 19.80mm, and annual rates ranged from 0.154 to 9.194mm/yr. Rates of erosion varied with lithology and the type of platform.Erosion on Type A mudstone platforms was 1.98mm/yr; on Type B mudstone platforms erosion was 0.733mm/yr; and on limestone platforms it was 0.88mm/yr. The grand mean lowering rate for all shore platforms was 1. 13mm/yr . These rates fall in the middle of the range of published rates from previous studies at Kaikoura and at locations around the world. For the fITst time, erosion data from a traversing micro-erosion meter were presented as volumes of material eroded.The total volume of rock eroded from study sites having, each with an area of 45.4cm 2 , ranged from 1.20 to 92.50cm 3 • A significant finding was that rock surfaces swell up as indicated by a rise in surface level rather than lowering from erosion. The maximum measured swelling was 8.90mm. At some measurement sites as much as 90 per cent of measurements showed swelling over a period of 98 days. Values for erosion and swelling were higher during summer months.Both erosion and swelling were shown to be statistically related to season, suggesting that weathering is the group of processes causing both erosion and swelling. Summer provides better conditions for wetting and drying, which is thought to be the most important weathering process on shore platforms. Horizontal retreat rates were calculated over 52 years for cliffs, beaches and lagoon deposits backing shore platforms at Kaikoura, these ranged from 0.05 to 0.91mJyr.Investigation of marine processes showed that the deep water wave environment off the Kaikoura Peninsula is very energetic, but the amount of wave energy delivered to platforms is very low. A comparison of deep water wave energy flux with wave energy flux at the landward cliff of platforms, showed that there was a reduction by as much as five orders of magnitude. An analysis of the role of breaking waves revealed that these were ineffective as an erosional agent ii because the depth of water offshore causes breaking well before waves arrive on platform surfaces. Shear stresses and dynamic forces under waves were calculated from waves measured on shore platforms. TIus showed that these forces never exceeded the compressive strength the platform rocks at Kaikoura. It was co...

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“…These previous studies have made use of a variety of techniques including various types of conductivity probe (Lamarre & Melville 1994;Hoque & Aoki 2005), acoustic techniques (Loewen et al 1996) and laser methods (Hwung et al 1992). In the present investigation we used optical fibre phase detection probes.…”

Section: Introductionmentioning

confidence: 99%

“…Several researchers including Hwung et al (1992), Hoque (2002), Cox & Shin (2003) and Hoque & Aoki (2005) have carried out more detailed laboratory investigations of the void fraction field in breaking waves, providing useful information about the vertical and horizontal distributions of void fraction. But by far the most comprehensive set of measurements was completed by Lamarre (1993) and is also reported by Lamarre & Melville (1991).…”

Section: Introductionmentioning

confidence: 99%

Void fraction measurements in breaking waves

2007

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This paper describes detailed measurements and analysis of the time-varying distribution of void fractions in three different breaking waves under laboratory conditions. The measurements were made with highly sensitive optical fibre phase detection probes and document the rapid spatial and temporal evolutions of both the bubble plume generated beneath the free surface and the splashes above. Integral properties of the measured void fraction fields reveal a remarkable degree of similarity between characteristics of the two-phase flow in different breaker types as they evolve with time. Depending on the breaker type, the energy expended in entraining air and generating splash accounts for a minimum of between 6.5 and 14% of the total energy dissipated during wave breaking.

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Energy Dissipation and Air Bubbles Mixing Inside Surf Zone

Cited by 15 publications

References 3 publications

Are breaking waves, bores, surges and jumps the same flow?

Are breaking waves, bores, surges and jumps the same flow?

Development of shore platforms on Kaikoura Peninsula, South Island, New Zealand

Void fraction measurements in breaking waves

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