Experimental study of local scour around subsea caissons in steady currents

Zhao, Ming; Zhu, Xiaosong; Cheng, Liang; Teng, Bin

doi:10.1016/j.coastaleng.2011.08.004

Cited by 64 publications

(30 citation statements)

References 15 publications

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“…During the three tests, scour depths at K M and K C were observed. In accordance with [13], the maximum scour depths throughout the tests were found at the upstream corners of the piles. As the local scour depth evolution is asymptotic [6], the tests were stopped when d M and d C grew only slightly.…”

Section: Introductionsupporting

confidence: 79%

“…The absence of an anti-clockwise damming in front of the submerged pile, along with additional water down wash on the side and behind the submerged pile, will change the horseshoe and wake vortex significantly. Thus, the main dynamics of sediment transport, including the horseshoe vortex, concentrated streamlines, and wake vortex will be changed [13]. Dey et al [14] conducted a series of experiments to study the influences of circular cross-section (CC) pile submergence on the scour depth under clear-water scour conditions.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, there is an absence of vortex shedding for the shorter pile of h c /D = 0.5. For the square cross-section (SC) piles, Zhao et al [13] observed that the scouring always starts at the two corners of the pile, and the bed level at the center of the upstream boundary remains almost unchanged before the scour pits extend there. Sarkar and Ratha [16] investigated the local scouring of non-uniform sediment beds around submerged CC and SC piles experimentally, but did not compare the different characteristics of the two pile shapes.…”

mentioning

confidence: 99%

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Comparisons of Local Scouring for Submerged Square and Circular Cross-Section Piles in Steady Currents

Liang

2019

Water

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The local scouring that occurs around submerged vertical piles in steady currents was studied experimentally in this paper. Three experiments were carried out for square cross-section (SC) piles and a circular cross-section (CC) pile with the same width. The key point scour depths, including the center of the upstream boundary point (K C ) and the two upstream corners (K M ), were observed over time. The two-dimensional profiles and the three-dimensional topography around each pile were measured using a Seatek. The different scouring characteristics of the SC and CC piles were investigated. The experiment results show that the scour depth at K C is much smaller than that of K M . The equilibrium scour depth of the CC pile is far less than that of the SC piles. The scour and deposition distributions were different between the CC and SC piles. The maximum scour depth was found at the lateral rear of the CC pile, and the maximum deposition was observed in sections of the SC piles. The evolutions of the scour depths at K M are predicted using a developed exponential equation.the scour depth will be independent from h c . By comparing the flow fields of h c /D = 0.5 and h c /D = 2.5, they found that the horseshoe vortex in front of the pile and the near-bed shear stress around the longer pile are stronger and wider in size, respectively. Moreover, there is an absence of vortex shedding for the shorter pile of h c /D = 0.5. For the square cross-section (SC) piles, Zhao et al. [13] observed that the scouring always starts at the two corners of the pile, and the bed level at the center of the upstream boundary remains almost unchanged before the scour pits extend there. Sarkar and Ratha [16] investigated the local scouring of non-uniform sediment beds around submerged CC and SC piles experimentally, but did not compare the different characteristics of the two pile shapes. Yao et al. [17] provided a relatively systematic report under live-bed scour conditions by carrying out a number of experiments. They found that the height-to-width ratio h c /D has a significant effect on the equilibrium scour depth and equilibrium time scale for the SC piles when h c /D is smaller than 4. Under their clear-water conditions, the Shields number was slightly smaller than the critical Shields number. The equilibrium time scale was found to reduce with an increase in the height-to-width ratio. Since the widths were not the same for the CC and SC piles, comparisons of the CC and SC piles were mainly conducted on the equilibrium time scale. Owing to the high flow intensity of the Shields number, the distributions of scouring and deposition for the two pile shapes did not show clear differences. Euler and Herget [18] stated that the size of the submerged piles and the approach flow velocity have significant effects on the scour hole shape and depth.Motivated by (i) the necessity of further research into the local scouring of submerged vertical piles, (ii) the significant effect of the flow intensity and pile height on local scouring, and (ii...

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Section: Introductionsupporting

confidence: 79%

Section: Introductionmentioning

confidence: 99%

mentioning

confidence: 99%

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Comparisons of Local Scouring for Submerged Square and Circular Cross-Section Piles in Steady Currents

Liang

2019

Water

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“…To this aim, this parameter was firstly estimated at 5.50E-05 kg m -2 s -1 based on experimental studies by Wang et al (2011), and linearly increased up to 1.26E-03 kg m -2 s -1 within 0.80 m from the upstream edges. This correction allowed to reproduce the scouring patterns observed by Zhao et al (2012) around a submerged cubic block hit by an orthogonal subcritical current.…”

Section: Small-scale Simulationsmentioning

confidence: 99%

Sediment transport modifications induced by submerged artificial reef systems: a case study for the Gulf of Venice

Bonaldo

Benetazzo

Bergamasco

et al. 2014

Oceanological and Hydrobiological Studies

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The shallow, gently sloping, sandy-silty seabed of the Venetian coast (Italy) is studded by a number of outcropping rocky systems of different size encouraging the development of peculiar zoobenthic biocenoses with considerably higher biodiversity indexes compared to neighbouring areas. In order to protect and enhance the growth of settling communities, artificial monolithic reefs were deployed close to the most important formations, providing further nesting sites and mechanical hindrance to illegal trawl fishing.In this framework, a multi-step and multi-scale numerical modelling activity was carried out to predict the perturbations induced by the presence of artificial structures on sediment transport over the outcroppings and their implications on turbidity and water quality. After having characterized wave and * Corresponding author e-mail: sandro.carniel@ismar.cnr.it current circulation climate at the sub-basin scale over a reference year, a set of small scale simulations was carried out to describe the effects of a single monolith under different geometries and hydrodynamic forcings, encompassing the conditions likely occurring at the study sites. A dedicated tool was then developed to compose the information contained in the small-scale database into realistic deployment configurations, and applied in four protected outcroppings identified as test sites. With reference to these cases, under current meteomarine climate the application highlighted a small and localised increase in suspended sediment concentration, suggesting that the implemented deployment strategy is not likely to produce harmful effects on turbidity close to the outcroppings.In a broader context, the activity is oriented at the tuning of a flexible instrument for supporting the decision-making process in benthic environments of outstanding environmental relevance, especially in the Integrated Coastal Zone Management or Maritime Spatial Planning applications. The dissemination of sub-basin scale modelling results via the THREDDS Data Server, together with an user-friendly software for composing single-monolith runs and a graphical interface for exploring the available data, significantly improves the quantitative information collection and sharing among scientists, stakeholders and policymakers.

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“…Water elevation η(x; t) is calculated using the Fourier transformation Some parameters of experimental tests (B4) [9] are as follows: Water depth Hn=50cm; Velocity in X axis Vx=32.5cm/s; Specific gravity (s)=2.67; Diameter D50 mm=0.135; Critical shields parameter=0.0625.…”

Section: Stokes and Cnoidal Waves Generatormentioning

confidence: 99%

Numerical Simulation 3D of Local Scour around Subsea Caisson Structures in Steady Currents and Waves

Hoang¹

2015

Proceedings of the 2015 International Conference on Modeling, Simulation and Applied Mathematics

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Abstract-This paper studied the local scour processes at subsea structures using using the computational fluid dynamics codes (OPENSOURCE CODE). The model solved the fully threedimensional, Reynolds-averaged Navier-Stokes equation closed with the LES model. Stokes and Cnoidal Waves were generated using Fenton's Fourier series method. Two empirical models must be used to compute the boundary layer at the interface and bed-load transport. We used the types of structured Cartesian grids. The velocity amplification at the corners is the dominant flow mechanism that controls the maximum scour depth. The results were agreement with the experimental study.

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Experimental study of local scour around subsea caissons in steady currents

Cited by 64 publications

References 15 publications

Comparisons of Local Scouring for Submerged Square and Circular Cross-Section Piles in Steady Currents

Comparisons of Local Scouring for Submerged Square and Circular Cross-Section Piles in Steady Currents

Sediment transport modifications induced by submerged artificial reef systems: a case study for the Gulf of Venice

Numerical Simulation 3D of Local Scour around Subsea Caisson Structures in Steady Currents and Waves

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