Breaking bore: Physical observations of roller characteristics

Leng, Xinqian; Chanson, Hubert

doi:10.1016/j.mechrescom.2015.02.008

Cited by 31 publications

(23 citation statements)

References 17 publications

(12 reference statements)

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“…The same data set showed that the toe perimeter shape fluctuated rapidly with transverse distance and time, and large fluctuations in bore celerity were observed. That is, the celerity of the roller toe fluctuated rapidly with both time and transverse distance, although in a quasi-two-dimensional manner on average (Leng and Chanson 2015b). Yet both laboratory and field observations hinted to the existence of large-scale three-dimensional bubbly structures (Leng and Chanson 2015a, Chanson 2016, Leng and Chanson 2016.…”

Section: Tidal Boresmentioning

confidence: 99%

“…It is believed that a more relevant analogy is the tidal breaking bore, as seen in Figure 2B. A breaking bore with a quasi-two-dimensional roller is observed for Froude numbers greater than 1.4 to 1.6 Chanson 2008, Leng andChanson 2015b), although localised form of breaking might appear for Froude numbers above 1.3 to 1.4, including shock waves upstream of and limited breaking at the first wave crest (Treske 1994, Chanson 2010a). In the field, tidal bores are typically observed for Froude numbers less than 2.5, as shown in Table 3.…”

Section: How Can Better Flow Analogies Help?mentioning

confidence: 99%

“…A steepening wave can propagate for a long distance before clearly breaking and developing a roller; so the crest kinematics still need to be elucidated in complex situations (3D, current, turbulence, wind, etc.). The transient evolution of the roller is crucial for future studies (Leng and Chanson 2015b). Future interests should also encompass bubble size distribution and dynamics, two-phase gas-liquid turbulence and LUBIN, P., and .…”

Section: How Can Better Flow Analogies Help?mentioning

confidence: 99%

See 2 more Smart Citations

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: Tidal Boresmentioning

confidence: 99%

Section: How Can Better Flow Analogies Help?mentioning

confidence: 99%

Section: How Can Better Flow Analogies Help?mentioning

confidence: 99%

See 1 more Smart Citation

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

Lubin

Chanson

2016

Environ Fluid Mech

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“…In addition, the biochemical properties of the water may be considered particularly in natural estuarine systems, as well as the sediment characteristics. In tidal bores, a Froude similitude is derived theoretically (Henderson 1966, Lighthill 1978, Leng and Chanson 2015. That is, the model and prototype Froude numbers must be equal.…”

Section: Physical Modelling and Experimental Setup Presentationmentioning

confidence: 99%

“…where V 1 is the initial flow velocity positive downstream, U is the bore celerity positive upstream, g is the gravity acceleration, A 1 is the initial flow cross-section area and B 1 is the initial free-surface width (Leng and Chanson 2015). For Fr 1 < 1.3 to1.4, the bore is undular: its front is followed by a train of quasi-periodic free-surface undulations (Peregrine 1966, Treske 1994.…”

Section: Introductionmentioning

confidence: 99%

Impact of a large cylindrical roughness on tidal bore propagation

2016

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Word count : 5,450 words. Abstract:A tidal bore is a hydrodynamic shock, surging upstream in some shallow-water bays and estuaries during the flood tide under large tidal range. This study investigates experimentally the propagation of tidal bores over a large cylindrical roughness element, representative of damaged bridge pier foundation. In the initially steady flow, the large cylindrical element generated a wake region, with extents comparable to steady flow literature. During the tidal bore propagation, the presence of the element had negligible effect on the free-surface properties, but a significant impact in terms of the instantaneous velocity and Reynolds stresses. This resulted in longer transient recirculation both upstream and downstream of the element and larger maximum velocity recirculation magnitudes, as well as enhanced turbulent stress levels and potential bed erosion around the large element, within two diameters from the element centre. The results showed the potential development of a large scour hole around the cylindrical element.

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Coupling between free-surface fluctuations, velocity fluctuations and turbulent Reynolds stresses during the upstream propagation of positive surges, bores and compression waves

Leng

Chanson

2015

Environ Fluid Mech

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In open channel, canals and rivers, a rapid increase in flow depth will induce a positive surge, also called bore or compression wave. The positive surge is a translating hydraulic jump. Herein new experiments were conducted in a large-size rectangular channel to characterise the unsteady turbulent properties, including the coupling between free-surface and velocity fluctuations. Experiments were repeated 25 times and the data analyses yielded the instantaneous median and instantaneous fluctuations of free-surface elevation, velocities and turbulent Reynolds stresses. The passage of the surge front was associated with large free-surface fluctuations, comparable to those observed in stationary hydraulic jumps, coupled with large instantaneous velocity fluctuations. The bore propagation was associated with large turbulent Reynolds stresses and instantaneous shear stress fluctuations, during the passage of the surge. A broad range of shear stress levels was observed underneath the bore front, with the probability density of the tangential stresses distributed normally and the normal stresses distributed in a skewed single-mode fashion. Maxima in normal and tangential stresses were observed shortly after the passage of a breaking bore roller toe. The maximum Reynolds stresses occurred after the occurrence of the maximum free-surface fluctuations, and this time lag implied some interaction between the free-surface fluctuations and shear stress fluctuations beneath the surge front, and possibly some causal effect.

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Breaking bore: Physical observations of roller characteristics

Cited by 31 publications

References 17 publications

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

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

Impact of a large cylindrical roughness on tidal bore propagation

Coupling between free-surface fluctuations, velocity fluctuations and turbulent Reynolds stresses during the upstream propagation of positive surges, bores and compression waves

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