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Large-scale experimental study on scour around offshore wind monopiles under irregular waves

Water Science and Engineering 2022年第1期15卷 40-46页

作者： Song-gui Chen En-yu Gong Xu Zhao Taro Arikawa Xin Chen Tianjin Research Institute for Water Transport Engineering Tianjin 300456China College of Water Resources and Civil Engineering China Agricultural UniversityBeijing 100083China Department of Civil and Environmental Engineering Chuo UniversityTokyo 112-8551Japan

The Keulegan-Carpenter(KC)number is the main dimensionless parameter that affects the local scour of offshore wind power monopile *** study conducted large-scale(1:13)physical model tests to study the local scour shape,equilibrium scour depth,and local scour volume of offshore wind power monopiles under the action of irregular waves with different KC *** experiments were carried out with the KC number ranging from 1.0 to *** a small KC number(KCscour mainly occurred on both cross-flow sides of the monopile with a low scour *** the KC number exceeded 4,the shape of the scour hole changed from a fan to an ellipse,and the maximum scour depth increased significantly with *** a large KC number(KC>6),the proposed method better predicted the equilibrium scour depth when the wave *** addition,according to the results of three-dimensional terrain scanning,the relationship between the local equilibrium scour volume of a single offshore wind power monopile and the KC number was *** provided a rational method for estimation of the riprap redundancy for monopile protection against scour.

关键词： Keulegan-Carpenter number Large-scale test scour hole shape equilibrium scour depth Local scour hole volume

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Effect of trapezoidal collars as a scour countermeasure around wing-wall abutments

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Water Science and Engineering 2018年第1期11卷 53-60页

作者： Payam Khosravinia Amir Malekpour Ali Hosseinzadehdalir Davod Farsadizadeh College of Agriculture University of KurdistanSanandaj 66177Iran College of Agricultural Sciences University of GuilanRasht 41996Iran College of Agriculture University of TabrizTabriz 51666Iran

Local scour around bridge abutments is a widespread problem that can result in structural failure. Collars can be used as a countermeasure to reduce the scour depth. In this study, the temporal scour development around a wing-wall abutment was investigated with and without collars. The tests were carried out under clear-water conditions for different abutment lengths, with collars of different sizes placed at the bed level. When no collar was used in the experiments, 70% of the maximum scour depth occurred in less than 2 h. However, when a collar with a width greater than the length of the abutment was used, no scour was observed for up to 200 min from the beginning of the experiments. The results show that an increase in the collar width not only led to a lag time for the onset of scouring but also reduced the maximum scour depth. Moreover, an increased collar width led to a better performance in mitigating scouring around smaller abutments. Generally, the scour depth decreased by 9%-37% with different collar widths.

关键词： scour development equilibrium scour depth Trapezoidal collar Wing-wall abutment Clear-water condition

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Development of current-induced scour beneath elevated subsea pipelines

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Journal of Ocean Engineering and Science 2018年第4期3卷 265-281页

作者： Jun Y.Lee Alexander L.Forrest Fauzi A.Hardjanto Shuhong Chai Remo Cossu Zhi Q.Leong National Centre for Maritime Engineering and Hydrodynamics Australian Maritime CollegeUniversity of TasmaniaLocked Bag 1395Launceston Tasmania 7250Australia Department of Civil and Environmental Engineering University of California-DavisDavisCA 95616United States School of Civil Engineering University of QueenslandSt Lucia Queensland 4072Australia

When scour occurs beneath a subsea pipeline and develops to a certain extent,the pipeline may experience vortex-induced vibrations,through which there can be a potential accumulation of fatigue ***,when a pipeline is laid on an uneven seabed,certain sections may have an elevation with respect to the far-field seabed,e o,at which the development of scour would *** work focused on predicting the development of the scour depth beneath subsea pipelines with an elevation under steady flow conditions.A range of pipe elevation-to-diameter ratios(i.e.0≤e o/D≤0.5)have been considered for laboratory experiments conducted in a sediment *** corresponding equilibrium scour depths and scour time scales were obtained;experimental data from published literature have been collected and added to the present study to produce a more complete analysis *** correlation between existing empirical equations for predicting the time scale and the experimental data was assessed,resulting in a new set of constants.A new manner of converting the scour time scale into a non-dimensional form was found to aid the empirical equations in attaining a better correlation to the experimental ***,a new empirical equation has also been proposed in this work,which accounts for the influence of e o/D on the non-dimensional scour time *** was found to have the best overall correlation with the experimental ***,full-scale predictions of the seabed gaps and time scales were made for the Tasmanian Gas Pipeline(TGP).

关键词： scour time scale equilibrium scour depth Subsea pipelines Pipe elevation Steady currents.

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Clear-water scour around semi-elliptical abutments with armored beds

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International Journal of Sediment Research 2010年第3期25卷 233-244页

作者： Hossein AFZALIMEHR Abdolreza Kabiri SAMANI Mehrnoosh MAHERANI Department of Water Engineering Isfahan University of Technology Department of Civil Engineering Isfahan University of Technology

Experimental study has been carried out under a clear-water scour condition to explore the local scour around semi-elliptical model bridge abutments with armor-layer bed, compared with the local scour process around semi-circular abutment. Two types of model bridge abutments, namely semi- elliptical and semi-circular abutments have been used in this experimental study. The model abutments had a ratio of streamwise length of abutment to the length of abutment transverse to the flow of 2 for semi-circular abutments and 3 for semi-elliptical abutments. In total, 50 Experiments have been designed and conducted under different flow conditions such as bed shear velocities, flow depth, and dimensions of bridge abutment model, as well as grain size of the bed material. Based on these experiments, the scour process around bridge abutments has been assessed. The dependence of the equilibrium scour depth of the scour hole on hydraulic variables has been studied. Empirical equation describing the equilibrium scour depth of the scour hole around bridge abutments has been developed.

关键词： Armor-layer equilibrium scour depth Local scour Particle grain size Semi-circular abutment Semi-elliptical abutment Shear velocity

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EFFECTS OF FLOW INTENSITY, OBSTACLE ALIGNMENT AND CROSS-SECTION GEOMETRY ON scour AT BRIDGE ABUTMENTS

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International Journal of Sediment Research 2002年第2期17卷 102-113页

作者： A. H. CARDOSO1, J. S. SANTOS2 and M. ROCA3 EFFECTS OF FLOW INTENSITY, OBSTACLE ALIGNMENT AND CROSS-SECTION GEOMETRY ON scour AT BRIDGE ABUTMENTS A. H. CARDOSO1, J. S. SANTOS2 and M. ROCA3 EFFECTS OF FLOW INTENSITY, OBSTACLE ALIGNMENT AND CROSS-SECTIO Associate Professor Instituto Superior Técnico Department of Civil Engineering and Architecture Av. Rovisco Pais 1049-001 Lisboa Civil Engineer GIBB Angola LAWGIBB group member Rua Augusto Tadeu Bastos 3 1° - 1 P.O. Box 35 I-C Luanda Teaching Assistant Universidad Politécnica de Catalunha Departamento de Ingenieria Hidráulica Marítima y Ambiental Jordi Girona1-3D1 08034 Barcelona

Experiments are reported on the effects of flow intensity, obstacle alignment and cross-section geometry on the equilibrium scour depth around abutments. The effect of flow intensity was studied for clear-water flow conditions, the obstacle alignment was studied for a wide range of angles of the obstacle with the flow direction, and tests on the cross-section geometry apply only to the case where the abutment extends into the main channel of a compound cross-section (two-stage channel). The channel bank and flood plain were built up with sand. The hypothesis of zero scour for flow velocities smaller than approximately 50% of the threshold velocity for the beginning of motion in the approaching flow cannot be rejected; maximum scour occurs for obstacles protruding at right angle from the cross-section walls, the reduction being small when obstacles point upstream; compared with rigid banks, the scour depth seems to be significantly reduced when channel bank and flood plain are constituted of alluvial material.

关键词： Flow intensity Obstacle alignment equilibrium scour depth Threshold velocity Flood plain

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