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Journal ArticleDOI

Characterization of breaking wave impact on vertical wall with recurve

04 May 2019-ISH Journal of Hydraulic Engineering (Taylor & Francis)-Vol. 25, Iss: 2, pp 153-161
Abstract: Large-scale experiments were conducted at the Coastal Research Centre (FZK), Germany to characterize the mechanics and characteristics of impact pressures due to breaking waves on a vertical sea wa...
Topics: Breaking wave (60%)
Citations
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Journal ArticleDOI
Abstract: This paper aims at investigating the intensity of the load applied by non-breaking waves on the recurved parapet wall of vertical breakwaters For this purpose, 2-D experiments were carried out on a simple vertical breakwater physical model with four different geometries of the parapet (with an “exit angle” of recurve of 0°, 45°, 60° and 90°), under both regular and irregular waves The tests showed the presence of loads of a quasi-static nature and loads with a typical church roof impulsive behaviour, depending on the (non breaking) wave characteristics and on the shape of the parapet This impulsive force resulted significantly larger than the quasi-static load of the pure vertical wall case The maximum measured total force under regular waves was compared with the one obtained by a numerical model based on IHFOAM For irregular waves with Hs equal to 80% of the freeboard, the maximum measured horizontal load on a 90° recurved wall is equivalent to the force applied by a constant pressure of order 5 ρgHs It was found, by analysing waves near the leading edge of a wave-group, that history effects are important, ie, in certain circumstances, a high wave preceded by lower waves generated a larger force than if it had been preceded by waves of the same height For regular tests, the largest impulsive forces occurred basically at the beginning of the tests, during the initial transient ramp-up period The irregular wave overtopping was also measured, showing good agreement with the existing predictive formulae and confirming the significant reduction of mean discharge with increasing exit angle and overhanging extension of the parapet

31 citations


Journal ArticleDOI
01 Apr 2020-Ocean Engineering
Abstract: A hybrid structure of pile-supported wharf connecting with pile breakwater is tested in a flume with a scale factor of 1:30. Based on generating regular and irregular waves and accurately reproducing bed profile by using pulverized coal, both wave, scour and load characteristic of this structure are investigated. When structure under wave impact, violent wave reflection is observed and wave transmission is small. With the large wave height and water depth, wave overtopping is significant and induces bigger green water height. Compared with bed without covering layer, rubble covering layer obviously decreases the scour range of bed profile. Pressures of the structure have distinct spatial distribution characteristics. The existing plates between piles of breakwater can easily trap the air during wave attack and induce significant impact pressure. Besides, superstructure of pile-supported wharf is mainly suffered from uplift pressure and attains the maximum pressure when air gap becomes zero. Due to dynamic response of structure, measured forces have smaller values and larger periods than integrated forces, and both horizontal and vertical measured forces decrease with increasing relative wave height. The findings and data presented here may be used by oceanic numerical modelers and engineers, for future research as well as predesign.

7 citations


Journal ArticleDOI
Abstract: Tidal flow has a significant influence on the mooring safety of vessels in deep-sea ports. In order to ensure the mooring safety of vessels, improving the structure form of the wharf can d...

5 citations


Journal ArticleDOI
01 Sep 2019-Ocean Engineering
Abstract: A well tested mathematical model is used to bring out important counter intuitive results on the aspect of reducing tsunami impact forces on on-shore buildings using sea dikes. The mathematical model is based on numerical solution of the general Reynolds Averaged Navier Stokes equations, with SST–k–ω model for turbulence closure. Tsunami waves are allowed to propagate on a 1 in 40 sloped beach and over-top a sea dike before impacting on buildings. The combined effect of various parameters such as position of the dike and shape and size of the dike has been studied, for sloping beaches. A sea dike placed far from the building may increase the tsunami impact force, if its size is not appropriate. It is found that a sea dike positioned close to the building offers best protection only if the height of the wave is small. If the wave height is large, there is an optimal distance at which the dike should be located for minimizing the tsunami impact force. Placing a second sea dike in addition to an existing sea dike may not reduce the tsunami impact force, if the location and size of the sea dikes are not appropriate.

4 citations


Journal ArticleDOI
TL;DR: It is indeed shown that the concrete quality plays a dominant role for the survivability of the structure, even allowing the design of a recurved concrete parapet without reinforcing steel bars.
Abstract: Several failures of recurved concrete crownwalls have been observed in recent years. This work aims to get a better insight within the processes underlying the loading phase of these structures due to non-breaking wave impulsive loading conditions and to identify the dominant failure modes. The investigation is carried out through an offline one-way coupling of computational fluid dynamics (CFD) generated wave pressure time series and a time-varying structural Finite Element Analysis. The recent failure of the Civitavecchia (Italy) recurved parapet is adopted as an explanatory case study. Modal analysis aimed to identify the main modal parameters such as natural frequencies, modal masses and modal shapes is firstly performed to comprehensively describe the dynamic response of the investigated structure. Following, the CFD generated pressure field time-series is applied to linear and non-linear finite element model, the developed maximum stresses and the development of cracks are properly captured in both models. Three non-linear analyses are performed in order to investigate the performance of the crownwall concrete class. Starting with higher quality concrete class, it is decreased until the formation of cracks is reached under the action of the same regular wave condition. It is indeed shown that the concrete quality plays a dominant role for the survivability of the structure, even allowing the design of a recurved concrete parapet without reinforcing steel bars.

4 citations


References
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Journal ArticleDOI
Abstract: Laboratory experiments were conducted to improve our understanding of the physics and characteristics of impact pressures due to collisions of breaking waves against a vertical wall. Measurements of impact wave pressures were performed simultaneously with observation of high-speed video pictures of the violent wave motion at the collision. The physics and characteristics of the impact pressure significantly depend on the colliding conditions of breaking waves. These were studied for the following colliding conditions: flip-through, collision of the vertical wave front, and plunging wave collision. When a small amount of air is entrapped between the breaking wave and the wall at the collision, the impact pressure increases considerably. The highest pressure, of very short duration, is observed when a vertical wave front strikes the wall while trapping a small amount of air in the form of either bubbles or a thin lens-shaped pocket. The impulsive pressure, occurring in the vicinity of the still water level, is transmitted downwards through the water body with the sound velocity. The larger the amount of the entrapped air at impact of the plunging breakers, the lower the magnitude and the longer the rise or compression time of the impact pressures. When plunging and curling of the breaking wave develop well, a thick air pocket is trapped, and damped pressure oscillations, due to the air pocket pulsation, appear immediately after the peak of the impact pressure. The oscillation frequencies are lower the greater the amount of entrapped air, and are almost equal to the resonant frequency of pulsating air pockets. The damping mechanisms, however, still remain unknown. Agreements between the measured and predicted oscillation frequencies suggest that adiabatic processes of the air pocket play an essential role in the physics of high impact pressure.

207 citations


"Characterization of breaking wave i..." refers background or methods or result in this paper

  • ...This may be due to decompression of compressed air pockets locked due to change in streamlining surface, conforming to the Hattori et al. (1994) and Kisacik (2012) observations....

    [...]

  • ...The experimental results of Hattori et al. (1994), Kirkgöz (1990) corresponds to small scale investigations, whereas Bullock et al. (2001) corresponds to large scale investigation....

    [...]

  • ...However, with advances in technology, Hattori et al. (1994), Kirkgöz (1995) and Lugni et al. (2006) used a visual observation method using high-speed cameras to quantify the spatial amount of entrapped air at the moment wave impinges the structure....

    [...]

  • ...Many researchers, including Schmidt et al. (1992), Hattori and Arami (1992), Hattori et al. (1994), Peregrine and Topliss (1994), and Kirkgöz (1995) have tried to observe the influence of the air entrained by a breaking wave....

    [...]

  • ...The comparison of best fit equations from the present investigation and from the earlier experimental works of Hattori et al. (1994), Kirkgöz (1990) and Bullock et al. (2001) are shown in Figure 8....

    [...]


Journal ArticleDOI
06 Dec 2006-Physics of Fluids
Abstract: The impact of waves upon a vertical, rigid wall during sloshing is analyzed with specific focus on the modes that lead to the generation of a flip-through [M. J. Cooker and D. H. Peregrine, “A model for breaking wave impact pressures,” in Proceedings of the 22nd International Conference on Coastal Engineering (ASCE, Delft, 1990), Vol. 2, pp. 1473–1486]. Experimental data, based on a time-resolved particle image velocimetry technique and on a novel free-surface tracking method [M. Miozzi, “Particle image velocimetry using feature tracking and Delaunay tessellation,” in Proceedings of the 12th International Symposium on Applications of Laser Techniques to Fluid Mechanics (2004)], are used to characterize the details of the flip-through dynamics while wave loads are computed by integrating the experimental pressure distributions. Three different flip-through modes are observed and studied in dependence on the amount and modes of air trapping. No air entrapment characterizes a “mode (a) flip-through,” engulfm...

149 citations


"Characterization of breaking wave i..." refers background or methods in this paper

  • ...(1994), Kirkgöz (1995) and Lugni et al. (2006) used a visual observation method using high-speed cameras to quantify the spatial amount of entrapped air at the moment wave impinges the structure. Researchers also started classifying the wave breaking based on the breaking criteria rather than wave type. Hull and Müller (2002) presented the resulting impact pressure based on the focusing of various wave shapes and Lugni et al. (2006) also reported that the shape of the impacting wave has a significant effect on wave impact pressure exerted on vertical walls....

    [...]

  • ...However, with advances in technology, Hattori et al. (1994), Kirkgöz (1995) and Lugni et al. (2006) used a visual observation method using high-speed cameras to quantify the spatial amount of entrapped air at the moment wave impinges the structure....

    [...]

  • ...(1994), Kirkgöz (1995) and Lugni et al. (2006) used a visual observation method using high-speed cameras to quantify the spatial amount of entrapped air at the moment wave impinges the structure. Researchers also started classifying the wave breaking based on the breaking criteria rather than wave type. Hull and Müller (2002) presented the resulting impact pressure based on the focusing of various wave shapes and Lugni et al. (2006) also reported that the shape of the impacting wave has a significant effect on wave impact pressure exerted on vertical walls. Oumeraci et al. (1993) comprehended the impact pressure into four major categories, namely non-breaking dynamic wave pressure, single sharp-peaked pressure, pressure oscillations with high frequencies, and pressure oscillations with low frequencies. Kisacik et al. (2012) implemented the ideology by Oumeraci et al. (1993) for the vertical wall with overhanging horizontal cantilever slab, and classified the breakers into slightly breaking wave (SBW), breaking wave small air trap (BWSAT), and breaking wave large air trap (BWLAT)....

    [...]

  • ...(1994), Kirkgöz (1995) and Lugni et al. (2006) used a visual observation method using high-speed cameras to quantify the spatial amount of entrapped air at the moment wave impinges the structure. Researchers also started classifying the wave breaking based on the breaking criteria rather than wave type. Hull and Müller (2002) presented the resulting impact pressure based on the focusing of various wave shapes and Lugni et al. (2006) also reported that the shape of the impacting wave has a significant effect on wave impact pressure exerted on vertical walls. Oumeraci et al. (1993) comprehended the impact pressure into four major categories, namely non-breaking dynamic wave pressure, single sharp-peaked pressure, pressure oscillations with high frequencies, and pressure oscillations with low frequencies....

    [...]

  • ...(1994), Kirkgöz (1995) and Lugni et al. (2006) used a visual observation method using high-speed cameras to quantify the spatial amount of entrapped air at the moment wave impinges the structure....

    [...]


Journal ArticleDOI
Abstract: Both laboratory and field tests that are described provide new information on the characteristics of wave impacts. Laboratory drop tests conducted using seawater and freshwater demonstrate that maximum impact pressures and rise times are influenced by both the level of aeration and the violence of the impact. A relationship is derived which enables the reduction in impact pressure caused by aeration to be estimated. This relationship is shown to provide a better means of predicting impact pressures in laboratory seawater wave tests from freshwater tests than either the Froude or Cauchy laws. Measurements are presented which show that, due to the different properties of seawater and freshwater, aeration levels are higher in seawater breakers than in freshwater breakers, even at a 1:25 model scale. The ways in which this affects the temporal variation in pressure and the scale relationships are discussed in some detail. Aeration and pressure measurements are also presented for full-scale wave impacts on a breakwater exposed to Atlantic waves. Attention is drawn to the likely role of expelled air and data included which indicate that the equivalent of up to 55% of entrained air does not necessarily prevent the occurrence of high impact pressures with short rise times.

134 citations


"Characterization of breaking wave i..." refers background or methods or result in this paper

  • ...(1994), Kirkgöz (1990) and Bullock et al. (2001) are shown in Figure 8....

    [...]

  • ...The experimental results of Hattori et al. (1994), Kirkgöz (1990) corresponds to small scale investigations, whereas Bullock et al. (2001) corresponds to large scale investigation....

    [...]

  • ...(1994), Kirkgöz (1990) and Bullock et al. (2001) are shown in Figure 8. The experimental results of Hattori et al. (1994), Kirkgöz (1990) corresponds to small scale investigations, whereas Bullock et al....

    [...]

  • ...The comparison of best fit equations from the present investigation and from the earlier experimental works of Hattori et al. (1994), Kirkgöz (1990) and Bullock et al. (2001) are shown in Figure 8....

    [...]

  • ...Hence, the present best fit equation is line with the full scale investigation results from Bullock et al. (2001)....

    [...]


Journal ArticleDOI
01 Jan 1995-Ocean Engineering
Abstract: The results of laboratory experiments on the maximum and bottom impact pressures from waves breaking directly on vertical and sloping faced coastal structures are presented. Direct wave breaking on a wall is classified as early, late, and perfect breaking. Although the present study is aimed at dealing with the type of impact resulting from the perfect breaking, to some extent the occurrence of early and late breaking are unavoidable. The wave impact pressures, therefore, have a random nature of variation from impact-to-impact under the same conditions. The maximum and bottom impact pressures on walls are treated statistically. The effects of the wall angle and foreshore slope on these two quantities are examined. The results show that for practical applications, the still-water level can be taken as the acting place for the maximum impact pressure on the wall. Simultaneous impact pressure distribution below and above still-water level may be approximated as parabolic and linear, respectively. Finally, using a wall deflection criterion, a water depth region in front of the wall is defined, where the breaking wave forces may reach a critical level.

81 citations


"Characterization of breaking wave i..." refers background or methods in this paper

  • ...Many researchers, including Schmidt et al. (1992), Hattori and Arami (1992), Hattori et al. (1994), Peregrine and Topliss (1994), and Kirkgöz (1995) have tried to observe the influence of the air entrained by a breaking wave....

    [...]

  • ...However, with advances in technology, Hattori et al. (1994), Kirkgöz (1995) and Lugni et al. (2006) used a visual observation method using high-speed cameras to quantify the spatial amount of entrapped air at the moment wave impinges the structure....

    [...]


Journal ArticleDOI
01 Jan 2002-Ocean Engineering
Abstract: The shape of breaking waves has a significant effect on wave impact pressures on vertical sea walls. In order to refine the results of previous researchers, a systematic study of breaker shapes and wave impact pressures on a vertical wall using a newly developed experimental technique, sequential flash photography, was conducted at Queen's University of Belfast. Assumptions, like the existence of a vertical flip-through jet or a parallel face impact, could not be confirmed. The maximum pressure was found to occur for plunging breakers and at Still Water Level (SWL), although high pressures can also occur for other breaker types above or below SWL.

78 citations


"Characterization of breaking wave i..." refers background or result in this paper

  • ...From the literature, it is inferred that the location of maximum impact pressure occurs in the region where the wave impinges the structure (Hull and Müller 2002)....

    [...]

  • ...From the literature, it is inferred that the location of maximum impact pressure occurs in the region where the wave impinges the structure (Hull and Müller 2002). However, from the above observation, it may also be based on the type of breaking. Mostly, for BWSAT & BWLAT waves tend to break exactly at SWL; for SBW case, slightly above SWL; waves start losing energy even before reaching the wall (Figure 3(a)), so wave breaks at a particular distance from location of wall (Figure 3(b)). The white spikes at the wave tongue clearly indicate this phenomenon. The occurrence of parallel faces is not observed during impact which is similar to the findings of Kisacik et al. (2012) and Hull and Müller (2002)....

    [...]

  • ...From the literature, it is inferred that the location of maximum impact pressure occurs in the region where the wave impinges the structure (Hull and Müller 2002). However, from the above observation, it may also be based on the type of breaking. Mostly, for BWSAT & BWLAT waves tend to break exactly at SWL; for SBW case, slightly above SWL; waves start losing energy even before reaching the wall (Figure 3(a)), so wave breaks at a particular distance from location of wall (Figure 3(b)). The white spikes at the wave tongue clearly indicate this phenomenon. The occurrence of parallel faces is not observed during impact which is similar to the findings of Kisacik et al. (2012) and Hull and Müller (2002). The accelerated water arrives earlier than wave crest enclosing a small amount of air between the wave crest and structure (Figure 3(c))....

    [...]

  • ...The occurrence of parallel faces is not observed during impact which is similar to the findings of Kisacik et al. (2012) and Hull and Müller (2002)....

    [...]

  • ...Hull and Müller (2002) presented the resulting impact pressure based on the focusing of various wave shapes and Lugni et al. (2006) also reported that the shape of the impacting wave has a significant effect on wave impact pressure exerted on vertical walls....

    [...]


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