Topic
Wave flume
About: Wave flume is a research topic. Over the lifetime, 1627 publications have been published within this topic receiving 23335 citations.
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01 May 2009TL;DR: In this paper, the authors analyzed wave reflection from permeable structures with a berm, including reshaping cases, based on the observation that for reflection, differently from what happens for overtopping and run-up, the whole slope below sea water level (SWL) is important, the slope to appear in the breaker parameter is evaluated as a weighted average of the structure slope below the berm level and the average slope in the run up/rundown area.
Abstract: This paper analyses wave reflection from permeable structures with a berm, including reshaping cases. Data are obtained from recent wave flume experiments and from 2DV numerical simulations performed with the COBRAS-UC code. The objectives of this research were to identify the proper representation of the average structure slope to be included in the breaker parameter and to check the performance of the formula for the reflection coefficient developed for straight slopes by the Authors. Based on the observation that for reflection, differently from what happens for overtopping and run-up, the whole slope below sea water level (SWL) is important, the slope to appear in the breaker parameter is evaluated as a weighted average of the structure slope below the berm level and the average slope in the run-up/run-down area. The inclusion of this slope in the proposed formula allows to extend its prediction capacity to structures with a berm and a fair agreement with both experiments and simulations is obtained.
11 citations
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TL;DR: In this article, the authors investigated the wave forces of tsunami on simplified onshore buildings at Penang Island and revealed that the nature of wave attack on building model depends on the relationship between model height and nominal height of the wave.
Abstract: In this study, wave forces of tsunami on simplified onshore buildings at Penang Island were investigated. Single-storey and double-storey buildings were downscaled at a ratio of 1:100 and subjected to tsunami bores of various runup heights in a 1 m x 1 m with 40 m long wave flume. Tsunami wave height and velocity at the location of building model were obtained. The experimental results revealed that the nature of wave attack on building model depends on the relationship between model height and nominal height of the wave. The time histories of forces in the horizontal and vertical direction and pressures on buildings due to simulated tsunami-like waves were measured. The relationships among the forces and pressures for the incident wave with nominal wave height around 40 mm were discussed in detail. It is observed that the maximum horizontal force and front pressure were attained when nominal height of the wave was achieved by the flow. The experimental results provide useful information for the dynamic analysis in the later stage of the study.
11 citations
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06 Sep 2006TL;DR: In this paper, the authors present some results obtained by using numerical models on the hydro-morphodynamic behaviour of such structural concept. They illustrate the observed interactions between the freeboard of the structure, its distance to the coast and the resulting wave field, induced circulation and sediment transport patterns.
Abstract: Submerged barriers are one of the most promising kind of shoreline protecting structures. The advantages offered vs. the conventional emerged structures are somehow off set because they are much more difficult to project. This decreases their use and limits their application potential. The paper presents some results, obtained by using numerical models on the hydro-morphodynamic behaviour of such structural concept. They illustrate the observed interactions between the freeboard of the structure, its distance to the coast and the resulting wave field, induced circulation and sediment transport patterns.
11 citations
01 Apr 2015
TL;DR: In this article, the authors investigated the placement pattern, packing density and wave over-topping over slope of a single-layer concrete unit called crablock in a 1:4/3 slope with the use of random and uniform placement.
Abstract: In the design of rubble mound breakwaters, nowadays single layer systems using concrete armour units have become more common practice compared to conventional two layer systems. However, after the introduction of the accropode in eighties, a small number of single layer armour units have been developed over the years; for example core-loc, A-jack, xbloc, accropode-II, cubipod and core-loc II. Recently, a new concrete armour unit called crablock has been invented and applied as one layer system in one damaged breakwater at Al Fujeirah, UAE. In contrast to other existing monolayer units, the shape of this unit is symmetrical which allows placing both in uniform and random pattern. As the crablock unit is still under development, no design guidance exists yet for this concrete armour unit. To use crablock as monolayer system the preliminary design guidance on placement of crablock, stability and wave overtopping are required. This led the present research to investigate the placement pattern, packing density and wave overtopping over slope to come with first design guidance for the application of crablock. It should be mentioned that stability of the crablock against wave attack was also looked at, but that will be reported by Mr. Andre Broere, an MSc-student at Delft University of Technology. The present research was based on a literature study, small scale dry placement tests and small scale hydraulic tests in a wave flume. Regarding to the review of literature studies on the existing single layer units and crablock, set up of dry placement tests and flume tests have been made for this experimental research. Dry placement tests as well as 2D wave flume tests were carried out at the Fluid Mechanics Laboratory of the Faculty of Civil Engineering and Geosciences at Delft University of Technology, Netherlands. Both placement and hydraulic tests were executed with the use of small units. In total 14 independent placement test series were executed to investigate the placement pattern, placing grid and packing density of crablock. All the tests were performed on a 1:4/3 slope with the use of random and uniform placement in a rectangular as well as in a diamond shaped placing grid. Results of placement tests showed that uniform placement of crablock is achievable with the use of relatively small and smooth under layer in a rectangular placing grid. The performance of regular placement using a conventional under layer with size 1/10th to 1/15th of the size of the armour layer was not so satisfactory. Furthermore, it was found that uniform pattern was hardly reachable in a diamond-shaped grid with conventional under layer. However, irregular placement of crablock was certainly easier to construct and possible to place with higher accuracy compared to uniform placement in a diamond grid. It should be noted that all the tests using a conventional underlayer were performed without the fixation of first row due to the difficulties in placement with model crablock units. If this can be fixated by designing dedicated toe units (both in rotation and location) it may perform better. Still, the large underlayer makes it difficult to place uniformly. Finally, two preferred placing patterns appeared from the placement tests, a regular pattern in a rectangular grid using a relatively small under layer and a random pattern in a diamond grid using a conventional under layer. For the determination of wave overtopping, altogether 14 different test series were performed in a wave flume. In this research, two constant spectral wave steepnesses of 0.02 and 0.04 were tested together with two different orientations of units, two different placing grids and four different packing densities. The preferred placing patterns were constructed in a wave flume on a modelled breakwater cross-section in front of the sloping foreshore of 1:30. Each test series was comprised of number of sub tests for specific wave height and period. In each test series, wave heights and periods were continued to measure until the failure of armour slope. The armour layer was reconstructed prior to start of each test series. The test results of 2D flume tests showed that wave overtopping over crablock slope did not vary much between the different test series with same wave steepness. Nevertheless, it was observed that wave overtopping is little bit higher for longer wave period that means for low steepness compared to short period. Based on test results, it was also found that overtopping behaviour does not really change with the change in packing density and also with different placement pattern of armour layer. Regarding to the comparison of relative overtopping rate over crablock armour between test results and empirical prediction, it was found that that empirical equation with assuming roughness factor of 0.45 underestimate the measured wave overtopping over crablock. However, the comparison between the test results on overtopping percentages and estimation by EurOtop (2007) proved that percentage of waves overtopped over crablock can be well predicted by using empirical formula. Furthermore, the measured wave overtopping over crablock slope was found slightly higher in comparison to CLASH (2004) results on other single layer units. This variation was mainly observed for the test results with low wave steepness. Besides relatively low wave steepness, most of the tests on crablock were performed with relatively longer wave periods in comparison to CLASH (2004) which was also one of the triggering factor for higher overtopping over crablock slope compared to CLASH (2004). Moreover, the use of sloping foreshore (1:30) instead of horizontal one by CLASH (2004) might also influence the overtopping behaviour. The 1:30 slope changed the shape of the waves and the waves at the structure toe showed a clear increase in velocity of the wave crest (near or at breaking) The resulting wave overtopping over crablock slope was also compared with the overtopping over xbloc slope measured by DMC (2003). From the comparison, it was found that wave overtopping over crablock is significantly lower compared to xbloc measurements by DMC (2003). Based on the comparison of wave overtopping over different armour slope with and without Ursell parameter, it was recognised that use of the Ursell parameter may explain wave period differences in some cases, but introduces also unexpected differences.
11 citations
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TL;DR: In this paper, the authors present the results of a 2D experimental model application of an alternative environment-friendly coastal structure, an inclined thin plate (ITP), and the primary objectives of this study were to understand (a) wave energy dissipation mechanism of ITP, (b) wave attenuation performance, and (c) the influence of the ITP on water particle (orbital) velocity characteristics.
11 citations