The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Ming-ming Liu - One of the best experts on this subject based on the ideXlab platform.
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numerical investigation of Local Scour around a vibrating pipeline under steady currents
Ocean Engineering, 2021Co-Authors: Ming-ming Liu, Lu Wang, Xin Jin, Fan Yang, Jinbo TangAbstract:Abstract A two-dimensional finite element numerical model was developed to predict Local Scour around a vibration submarine pipeline in steady current. The numerical model was based on incompressible two-dimensional Navier-Stokes equations with a Shear-Stress Transport (SST) k-ω turbulence model closure. The transportations of suspended load and the bed load were taken into consideration in the present numerical simulation. The moving boundaries induced by the vibration pipeline and the evolution of the seabed due to Local Scour were tracked by using the Arbitrary Lagrangian Eulerian (ALE) method. Comparisons between the numerical results and available experimental data showed satisfactory agreements. The Local Scour around a vibrating pipeline has been investigated, including the maximum Scour depth below the pipeline, the vortex shedding mode and the vibration amplitude of the pipeline. The numerical results showed that the maximum vibration amplitude of the pipeline could be about 1.2D, and the maximum Scour depth occurred in the wake side of the vibration pipeline.
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Local Scour around two subsea pipelines in an oscillatory flow
Scour and Erosion, 2016Co-Authors: Ming Zhao, Ming-ming Liu, Liang Cheng, Scott DraperAbstract:In offshore engineering, wave generated flows are generally modelled as oscillatory flows when flow around small scale cylindrical structures are considered. The understanding of Local Scour around subsea pipelines under waves is important to ensure the stability of pipelines. In this study, Local Scour around two identical pipelines in a tandem arrangement in an oscillatory flow is investigated numerically. The flow around the pipelines is simulated by the Reynolds-averaged Navier-Stokes (RANS) equations and the Local Scour is predicted by solving the conservation equation of the sediment mass. The numerical model is firstly validated against experimental data. Then, the effects of the gap between the two pipelines and the KC number on the Scour depth below the pipelines are examined over a wide parameter space.
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Numerical modeling of Local Scour and forces for submarine pipeline under surface waves
Coastal Engineering, 2016Co-Authors: Ming-ming Liu, Ming Zhao, Bin Teng, Guoqiang TangAbstract:Abstract A two-dimensional numerical model is developed to predict Local Scour around submarine pipelines induced by the orbital fluid motion under surface water waves. Instead of being simplified to oscillatory flow, the wave motion is modeled using a fully nonlinear wave model. The numerical model is based on the two-dimensional Reynolds-Averaged Navier–Stokes (RANS) equations with a Shear-Stress Transport (SST) k-ω turbulence closure. Both suspended load and bed load sediment transportations are considered. The moving boundaries of free surface and the evolution of seabed due to Local Scour are tracked using the Arbitrary Lagrangian–Eulerian (ALE) method. The Streamline Upwind Petrov–Galerkin Finite Element Method (SUPG-FEM) is used to discretize the governing equations. The numerical model is validated against the benchmarks of linear and nonlinear wave propagations and their interactions with submerged structures as well as Local Scour around submarine pipeline in steady current. Comparisons between the numerical results and available theoretical, numerical and experimental data show satisfactory agreements. The proposed numerical model is then used to investigate the nonlinear wave-induced Local Scour around pipelines placed flat and sloping seabed. The effects of wave height and wave period on Local Scour and wave forces on the pipelines are examined. The numerical investigations suggest the necessity of utilizing the free surface wave model rather than the simplified oscillatory flow model for the problem of Local Scour around submarine pipelines in case of large amplitude nonlinear waves and pipelines over uneven seabed.
Bruce W. Melville - One of the best experts on this subject based on the ideXlab platform.
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Local Scour at Downstream Sloped Submerged Weirs
Journal of Hydraulic Engineering, 2018Co-Authors: Lu Wang, Bruce W. Melville, Dawei Guan, Colin WhittakerAbstract:AbstractThis paper presents an experimental study of Local Scour at submerged weirs with different downstream slopes. Thirty-three tests of coarse sand (d50=0.85 mm) and 24 tests of fine sand (d50...
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clear water Local Scour at skewed complex bridge piers
Journal of Hydraulic Engineering, 2018Co-Authors: Yifan Yang, Bruce W. Melville, D M Sheppard, Asaad Y ShamseldinAbstract:AbstractAn experimental study on flow-induced clear-water Local Scour at complex bridge piers was conducted using two typical pier models, nine pile-cap elevations, and seven pier skew angles from ...
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THE PHYSICS OF Local Scour AT BRIDGE PIERS
2008Co-Authors: Bruce W. MelvilleAbstract:The relation between the depth of Local Scour at a bridge pier and its dependent parameters is discussed. The dependent parameters describe the flood flow and bed sediment characteristics, the geometry of the bridge pier and the rate of development of Local Scour. Emphasis is given to the underlying physics of the process of Local Scour. Recent research findings are included. Limitations in knowledge of the process are noted. The discussion is restricted to Local Scour at unsubmerged bridges in straight channels with beds comprising homogeneous, alluvial sediments. Flow contraction effects are assumed to be absent. Superstructure submergence effects are considered separately. Additional factors, such as sediment cohesion, layered strata, bedrock effects and Scour at bridges subjected to tidal flows and waves are not considered.
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Local Scour at Complex Piers
World Environmental and Water Resource Congress 2006, 2006Co-Authors: Bruce W. Melville, Stephen E. Coleman, Stephen PriestleyAbstract:A methodology to predict Local Scour depth at a complex pier is presented that recognises the relative Scouring potentials of the components of complex piers, and the transition of Scouring processes occurring for varying pile-cap elevation. Scour depths are predicted over the entire range of possible pile-cap elevations using a combination of existing expressions for Scouring respectively at uniform piers, caisson-founded piers, pile groups with debris rafts, and pile groups alone. The validity of the method is confirmed using measurements of Local Scour at complex piers, and a case study is used to highlight application of the methodology. For design purposes, the method highlights respective pile-cap elevations that maximise (i.e. to be avoided over the pier life) and minimise Local Scour at complex piers. The method reinforces that where the pile-cap elevation relative to the bed can vary with time at a bridge site, potential Local-Scour depths need to be assessed over the range of possible pile-cap elevations for the pier.
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time scale for Local Scour at bridge piers
Journal of Hydraulic Engineering, 2000Co-Authors: Bruce W. Melville, Yee-meng ChiewAbstract:The temporal development of clear-water Local Scour depth at cylindrical bridge piers in uniform sand beds is considered. New data are presented and used to quantify the influence of flow duration on the depth of Local Scour. An equilibrium time scale (t*) is defined. The data show that both t* and the equilibrium Scour depth (dse) are subject to similar influences of flow and sediment parameters, as might be expected because they are inherently interdependent. A method is given for determination of the time for development of dse for a given pier, sediment, and approach flow velocity and the concomitant estimation of the Scour depth at any stage during development of the equilibrium Scour hole. The results show that the Scour depth after 10% of the time to equilibrium is between about 50% and 80% of the equilibrium Scour depth, depending on the approach flow velocity. of Local Scour d se is rapidly attained in live-bed conditions, but rather more slowly in clear-water conditions (Fig. 1). Clear- water Scour occurs for mean flow velocities up to the threshold velocity for bed sediment entrainment, i.e., V # Vc, while live- bed Scour occurs for V > Vc. The maximum equilibrium Scour depth dse)max occurs at V = Vc. In armored cobble or cohesive sediment bed streams, multiple flood events may be required before the maximum clear-water Scour is reached. This may take many years. The equilibrium Scour depth in live-bed con- ditions fluctuates due to the effects of bed form migration. The dashed lines in Fig. 1 represent the temporal average Scour depth under live-bed conditions. The diagram also shows the time taken, te, for the equilibrium Scour depth to develop. The equilibrium time, te, is the focus of this paper. It increases rapidly with flow velocity under clear-water conditions, but then decreases rapidly for live-bed Scour. Existing equations for depth of Local Scour at bridge piers give the equilibrium depth and are therefore conservative re- garding temporal effects. For the live-bed conditions that typ- ically pertain in floods, equilibrium Scour depths are appro- priate. However, where clear-water Scour conditions exist, the equilibrium depth of Scour may be overly conservative. Peak flood flows may last only a number of hours or a few days in the field, and short floods have insufficient time to generate equilibrium depths. For example, bridge piers situated on the floodplain may be wet for periods of less than one day during a flood; typically, clear-water conditions pertain at such sites. The actual Scour may be only a small fraction of the equilib- rium Scour depth, which could take weeks to fully develop. Johnson and McCuen (1991) developed an analytical model to simulate the temporal process of Local Scour at piers. The model was applied to a hypothetical bridge pier using a gen- erated sequence of flood flows over a 75 year period, the in- dividual storms being of 24 h duration. At the end of the 75 year period, the Scour depth was still increasing.
Guoqiang Tang - One of the best experts on this subject based on the ideXlab platform.
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detecting Local Scour using contact image sensors
Journal of Hydraulic Engineering, 2017Co-Authors: Weidong Yao, Ming Zhao, Liang Cheng, Scott Draper, Guoqiang Tang, Yu Shrike Zhang, Philip HortinAbstract:AbstractThe paper presents a novel contact image sensor (CIS) to monitor the Local Scour process around a model pile in water flows. The CIS is an optical sensor that tracks the evolution of the in...
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Numerical modeling of Local Scour and forces for submarine pipeline under surface waves
Coastal Engineering, 2016Co-Authors: Ming-ming Liu, Ming Zhao, Bin Teng, Guoqiang TangAbstract:Abstract A two-dimensional numerical model is developed to predict Local Scour around submarine pipelines induced by the orbital fluid motion under surface water waves. Instead of being simplified to oscillatory flow, the wave motion is modeled using a fully nonlinear wave model. The numerical model is based on the two-dimensional Reynolds-Averaged Navier–Stokes (RANS) equations with a Shear-Stress Transport (SST) k-ω turbulence closure. Both suspended load and bed load sediment transportations are considered. The moving boundaries of free surface and the evolution of seabed due to Local Scour are tracked using the Arbitrary Lagrangian–Eulerian (ALE) method. The Streamline Upwind Petrov–Galerkin Finite Element Method (SUPG-FEM) is used to discretize the governing equations. The numerical model is validated against the benchmarks of linear and nonlinear wave propagations and their interactions with submerged structures as well as Local Scour around submarine pipeline in steady current. Comparisons between the numerical results and available theoretical, numerical and experimental data show satisfactory agreements. The proposed numerical model is then used to investigate the nonlinear wave-induced Local Scour around pipelines placed flat and sloping seabed. The effects of wave height and wave period on Local Scour and wave forces on the pipelines are examined. The numerical investigations suggest the necessity of utilizing the free surface wave model rather than the simplified oscillatory flow model for the problem of Local Scour around submarine pipelines in case of large amplitude nonlinear waves and pipelines over uneven seabed.
Yee-meng Chiew - One of the best experts on this subject based on the ideXlab platform.
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Local Scour and Flow Characteristics around Pipeline Subjected to Vortex-Induced Vibrations
Journal of Hydraulic Engineering, 2020Co-Authors: Dawei Guan, Yee-meng Chiew, Shih-chun Hsieh, Ying Min Low, Maoxing WeiAbstract:AbstractAlthough Local Scour around submarine pipelines has been extensively studied in the last few decades, understanding of the mechanism of Local Scour around pipelines is still in its infancy ...
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time scale for Local Scour at bridge piers
Journal of Hydraulic Engineering, 2000Co-Authors: Bruce W. Melville, Yee-meng ChiewAbstract:The temporal development of clear-water Local Scour depth at cylindrical bridge piers in uniform sand beds is considered. New data are presented and used to quantify the influence of flow duration on the depth of Local Scour. An equilibrium time scale (t*) is defined. The data show that both t* and the equilibrium Scour depth (dse) are subject to similar influences of flow and sediment parameters, as might be expected because they are inherently interdependent. A method is given for determination of the time for development of dse for a given pier, sediment, and approach flow velocity and the concomitant estimation of the Scour depth at any stage during development of the equilibrium Scour hole. The results show that the Scour depth after 10% of the time to equilibrium is between about 50% and 80% of the equilibrium Scour depth, depending on the approach flow velocity. of Local Scour d se is rapidly attained in live-bed conditions, but rather more slowly in clear-water conditions (Fig. 1). Clear- water Scour occurs for mean flow velocities up to the threshold velocity for bed sediment entrainment, i.e., V # Vc, while live- bed Scour occurs for V > Vc. The maximum equilibrium Scour depth dse)max occurs at V = Vc. In armored cobble or cohesive sediment bed streams, multiple flood events may be required before the maximum clear-water Scour is reached. This may take many years. The equilibrium Scour depth in live-bed con- ditions fluctuates due to the effects of bed form migration. The dashed lines in Fig. 1 represent the temporal average Scour depth under live-bed conditions. The diagram also shows the time taken, te, for the equilibrium Scour depth to develop. The equilibrium time, te, is the focus of this paper. It increases rapidly with flow velocity under clear-water conditions, but then decreases rapidly for live-bed Scour. Existing equations for depth of Local Scour at bridge piers give the equilibrium depth and are therefore conservative re- garding temporal effects. For the live-bed conditions that typ- ically pertain in floods, equilibrium Scour depths are appro- priate. However, where clear-water Scour conditions exist, the equilibrium depth of Scour may be overly conservative. Peak flood flows may last only a number of hours or a few days in the field, and short floods have insufficient time to generate equilibrium depths. For example, bridge piers situated on the floodplain may be wet for periods of less than one day during a flood; typically, clear-water conditions pertain at such sites. The actual Scour may be only a small fraction of the equilib- rium Scour depth, which could take weeks to fully develop. Johnson and McCuen (1991) developed an analytical model to simulate the temporal process of Local Scour at piers. The model was applied to a hypothetical bridge pier using a gen- erated sequence of flood flows over a 75 year period, the in- dividual storms being of 24 h duration. At the end of the 75 year period, the Scour depth was still increasing.
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Temporal Development of Local Scour at Bridge Piers
1999Co-Authors: Yee-meng Chiew, Bruce W. MelvilleAbstract:The temporal development of Local Scour depth at circular cylindrical bridge piers is considered. New data are presented and used to quantify the influence of flow duration on the depth of Local Scour under clear-water conditions. A method is given for determination of the time for development of the equilibrium depth of Scour for a given pier, sediment and approach flow velocity and the concomitant estimation of the Scour depth at any stage during development of the equilibrium Scour hole. The results show that the Scour depth after 10% of the time to equilibrium is between about 55% and 80% of the equilibrium Scour depth, depending on the approach flow velocity.
Nasir Ahmad Rather - One of the best experts on this subject based on the ideXlab platform.
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Significance of Shape Factor of Obstacle on Local Scour
Iranian Journal of Science and Technology Transactions of Civil Engineering, 2019Co-Authors: Bintul Huda Mir, Mohd Akbar Lone, Nasir Ahmad RatherAbstract:The main goal of this research was to determine the effect of shape factor of obstacle on Local Scour. The research aimed at better quantification of Local Scour depth with respect to obstacle shape and bed material variations. The shape factor has been defined as a ratio of Scour of any shape to the Scour of circular shape under similar conditions. Four different shapes and five different bed materials were used in the study. The shape factors were computed for all the shapes in each bed material used, and the shape factor for a particular shape was found to remain almost unaffected for different bed materials and the flow parameters. On the basis of this research work, a relation was developed for the estimation of Local Scour, taking into account the effect of shape factor along with other factors responsible for the Scour phenomenon. The model so developed was validated for different bed materials and different obstacle shapes with the help of Breusers model.
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Effect of Gradation of Bed Material on Local Scour Depth
Geotechnical and Geological Engineering, 2018Co-Authors: Bintul Huda Mir, Mohd Akbar Lone, Javeed Ahmad Bhat, Nasir Ahmad RatherAbstract:The paper presents a study on Local Scour with respect to bed material gradation, flow depth and the Froude number. In the study, bed materials collected from five different rivers were used separately for four different shapes of the obstructions. The water discharge was also varied for each run. The experimental results obtained, reveal the dependence of Local Scour on the overall bed material gradation, and shape of the obstruction, especially the upstream interface. The models developed on basis of the experimental findings for different shapes are more realistic than the widely adopted criteria which mainly consider only effective size, d _50 of the bed material, ignoring the other gradation parameters. Moreover, it was found that the obstruction shape also affects the Scour phenomenon considerably.