Three-dimensional scour below offshore pipelines in steady currents

Cheng, Liang; Yeow, Kervin; Zhang, Zhipeng; Teng, Bin

doi:10.1016/j.coastaleng.2008.12.004

Cited by 80 publications

(109 citation statements)

References 10 publications

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“…The scour propagation velocity (V h ) along the pipeline was obtained by analysing the time dependent scour depths of each individual probe installed on the model pipeline in the same manner as that reported by Cheng et al (2009).…”

Section: Wave Only Conditionsmentioning

confidence: 99%

“…A simple levelling device, previously used in Cheng et al (2009), was used to ensure consistent embedment depth along the full length of the model pipeline. A small hole (also called worm hole) was dug underneath the model pipe at the middle section of the pipeline to allow scour propagation in both directions towards the flume walls.…”

Section: Experiments Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…The work reported in this paper can be considered as an extension of the investigation by Cheng et al (2009). Local scour depths directly below the model pipeline were measured using conductivity scour probes in the same way as described in Cheng et al (2009). Relationships between the scour propagation rate (V h ) and the key parameters such as the Keuglegan-Carpenter number (KC), embedment depth (e/D) and wave angle of attack are established.…”

Section: Introductionmentioning

confidence: 99%

“…This model was later improved by Hansen et al (1991) to account for parameters that may slow down the scouring process such as pipeline embedment and sagging. Cheng et al (2009) conducted an experimental investigation on the propagation of scour along pipelines subject to steady currents under live-bed conditions. Physical model experiments were conducted to quantify the effects of various parameters on scour propagation velocities along the pipeline.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

3D scour below pipelines under waves and combined waves and currents

Cheng

Yeow

Zang

et al. 2014

Coastal Engineering

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This paper presents the results of an experimental investigation on three-dimensional local scour below a rigid pipeline subjected to wave only and combined wave and current conditions. The tests were conducted in a conventional wave flume. The major emphasis of the investigation was on the scour propagation speed (free span expansion rate) along the pipeline after local scour was initiated at a controlled location. The effects of flow ratio (steady current velocity vs. combined waves/current velocity), flow incidence angle and pipeline initial embedment depth on free span expansion rate were investigated. It was observed that the scour along the pipeline propagated at a constant rate under wave only conditions. The scour propagation rate decreased with increasing embedment depth, however, increased with the increasing Keuglegan-Carpenter (KC) number. Under combined wave and current conditions, the effect of velocity ratio on scour propagation velocity along the pipeline was quantified. Empirical relationships between the scour propagation rate (V h ) and key parameters such as the KC number and embedment depth (e/D) were established based on the testing results.

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Section: Wave Only Conditionsmentioning

confidence: 99%

Section: Experiments Setupmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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3D scour below pipelines under waves and combined waves and currents

Cheng

Yeow

Zang

et al. 2014

Coastal Engineering

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Numerical study on local scour characteristics around submarine pipelines in the Yellow River Delta silty sandy soil under waves and currents

Yu,

Hu,

Zhang

et al. 2024

Deep Underground Science and Engineering

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Due to their high reliability and cost‐efficiency, submarine pipelines are widely used in offshore oil and gas resource engineering. Due to the interaction of waves, currents, seabed, and pipeline structures, the soil around submarine pipelines is prone to local scour, severely affecting their operational safety. With the Yellow River Delta as the research area and based on the renormalized group (RNG) k‐ε turbulence model and Stokes fifth‐order wave theory, this study solves the Navier–Stokes (N–S) equation using the finite difference method. The volume of fluid (VOF) method is used to describe the fluid‐free surface, and a three‐dimensional numerical model of currents and waves–submarine pipeline–silty sandy seabed is established. The rationality of the numerical model is verified using a self‐built waveflow flume. On this basis, in this study, the local scour development and characteristics of submarine pipelines in the Yellow River Delta silty sandy seabed in the prototype environment are explored and the influence of the presence of pipelines on hydrodynamic features such as surrounding flow field, shear stress, and turbulence intensity is analyzed. The results indicate that (1) local scour around submarine pipelines can be divided into three stages: rapid scour, slow scour, and stable scour. The maximum scour depth occurs directly below the pipeline, and the shape of the scour pits is asymmetric. (2) As the water depth decreases and the pipeline suspension height increases, the scour becomes more intense. (3) When currents go through a pipeline, a clear stagnation point is formed in front of the pipeline, and the flow velocity is positively correlated with the depth of scour. This study can provide a valuable reference for the protection of submarine pipelines in this area.

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Experimental studies of local scour in the pressurized OCF below a wooden log across the flow

Maji

Hanmaiahgari

Dey

2014

Sadhana

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The proposed study examined and reviewed the published experimental results related to clear water scour below a cylinder across the flow. It also highlighted the limitations of existing methods for estimating the scour depth below a submerged cylinder. In the present study, experiments were performed for 50% and 75% submergences of a 70 mm diameter cylinder in the free surface flow over a uniform sand bed with d 50 = 0.98 mm downstream of an apron. Based on the experimental results, an empirical equation was proposed to estimate the amount of gap flow between the cylinder and the bed for an equilibrium scour for a given flow depth and sediment properties. Measured scour profile consisted of a scour hole and immediately followed by a dune. However, no general sediment transport was occurring away from the cylinder due to the undisturbed bed shear stress less than or equal to the critical shear stress required for the sediment entrainment. Different submergence ratios of the cylinder resulted in different longitudinal and vertical extensions of the scour hole and the dune. The maximum equilibrium scour depth occurred when the cylinder is fully submerged in the unidirectional flow with water depth equals to the cylinder diameter. The non-dimensional measured scour profiles were found to be similar. The characteristic lengths of the scour hole and the dune were computed analytically by approximating the measured scour profile by third degree polynomials. The computed non-dimensional scour profiles compared satisfactorily with the measured profiles. It was found that analytical non-dimensional scour profiles were identical for a given diameter of a cylinder with different submergences for the same flow conditions.

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Three-dimensional scour below offshore pipelines in steady currents

Cited by 80 publications

References 10 publications

3D scour below pipelines under waves and combined waves and currents

3D scour below pipelines under waves and combined waves and currents

Numerical study on local scour characteristics around submarine pipelines in the Yellow River Delta silty sandy soil under waves and currents

Experimental studies of local scour in the pressurized OCF below a wooden log across the flow

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