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    Near-Bed Flow Mechanisms Around a Circular Marine Pipeline Close to a Flat Seabed in the Subcritical Flow Regime Using a k-ɛ Model

    Source: Journal of Offshore Mechanics and Arctic Engineering:;2012:;volume( 134 ):;issue: 002::page 21803
    Author:
    Muk Chen Ong
    ,
    Torbjørn Utnes
    ,
    Lars Erik
    ,
    Dag Myrhaug
    ,
    Bjørnar Pettersen
    DOI: 10.1115/1.4004631
    Publisher: The American Society of Mechanical Engineers (ASME)
    Abstract: Flow mechanisms around a two-dimensional (2D) circular marine pipeline close to a flat seabed have been investigated using the 2D unsteady Reynolds-averaged Navier–Stokes (URANS) equations with a standard high Reynolds number k-ɛ model. The Reynolds number (based on the free stream velocity and cylinder diameter) ranges from 1 × 104 to 4.8 × 104 in the subcritical flow regime. The objective of the present study is to show a thorough documentation of the applicability of the k-ɛ model for engineering design within this flow regime by means of a careful comparison with available experimental data. The inflow boundary layer thickness and the Reynolds numbers in the present simulations are set according to published experimental data, with which the simulations are compared. Detailed comparisons with the experimental data for small gap ratios are provided and discussed. The effects of the gap to diameter ratio and the inflow boundary layer thickness have been studied. Although under-predictions of the essential hydrodynamic quantities (e.g., time-averaged drag coefficient, time-averaged lift coefficient, root-mean-square fluctuating lift coefficient, and mean pressure coefficient at the back of the pipeline) are observed due to the limitation of the turbulence model, the present approach is capable of providing good qualitative agreement with the published experimental data. The vortex shedding mechanisms have been investigated, and satisfactory predictions are obtained. The mean pressure coefficient and the mean friction velocity along the flat seabed are predicted reasonably well as compared with published experimental and numerical results. The mean seabed friction velocity at the gap is much larger for small gaps than for large gaps; thus, the bedload sediment transport is much larger for small gaps than for large gaps.
    keyword(s): Flow (Dynamics) , Pipelines , Underwater pipelines , Seabed , Vortex shedding , Mechanisms , Pressure , Engineering simulation , Boundary layers , Cylinders , Reynolds number , Sediments , Thickness AND Turbulence ,
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      Near-Bed Flow Mechanisms Around a Circular Marine Pipeline Close to a Flat Seabed in the Subcritical Flow Regime Using a k-ɛ Model

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    http://yetl.yabesh.ir/yetl1/handle/yetl/150002
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    • Journal of Offshore Mechanics and Arctic Engineering

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    contributor authorMuk Chen Ong
    contributor authorTorbjørn Utnes
    contributor authorLars Erik
    contributor authorDag Myrhaug
    contributor authorBjørnar Pettersen
    date accessioned2017-05-09T00:53:46Z
    date available2017-05-09T00:53:46Z
    date copyrightMay, 2012
    date issued2012
    identifier issn0892-7219
    identifier otherJMOEEX-28394#021803_1.pdf
    identifier urihttp://yetl.yabesh.ir/yetl/handle/yetl/150002
    description abstractFlow mechanisms around a two-dimensional (2D) circular marine pipeline close to a flat seabed have been investigated using the 2D unsteady Reynolds-averaged Navier–Stokes (URANS) equations with a standard high Reynolds number k-ɛ model. The Reynolds number (based on the free stream velocity and cylinder diameter) ranges from 1 × 104 to 4.8 × 104 in the subcritical flow regime. The objective of the present study is to show a thorough documentation of the applicability of the k-ɛ model for engineering design within this flow regime by means of a careful comparison with available experimental data. The inflow boundary layer thickness and the Reynolds numbers in the present simulations are set according to published experimental data, with which the simulations are compared. Detailed comparisons with the experimental data for small gap ratios are provided and discussed. The effects of the gap to diameter ratio and the inflow boundary layer thickness have been studied. Although under-predictions of the essential hydrodynamic quantities (e.g., time-averaged drag coefficient, time-averaged lift coefficient, root-mean-square fluctuating lift coefficient, and mean pressure coefficient at the back of the pipeline) are observed due to the limitation of the turbulence model, the present approach is capable of providing good qualitative agreement with the published experimental data. The vortex shedding mechanisms have been investigated, and satisfactory predictions are obtained. The mean pressure coefficient and the mean friction velocity along the flat seabed are predicted reasonably well as compared with published experimental and numerical results. The mean seabed friction velocity at the gap is much larger for small gaps than for large gaps; thus, the bedload sediment transport is much larger for small gaps than for large gaps.
    publisherThe American Society of Mechanical Engineers (ASME)
    titleNear-Bed Flow Mechanisms Around a Circular Marine Pipeline Close to a Flat Seabed in the Subcritical Flow Regime Using a k-ɛ Model
    typeJournal Paper
    journal volume134
    journal issue2
    journal titleJournal of Offshore Mechanics and Arctic Engineering
    identifier doi10.1115/1.4004631
    journal fristpage21803
    identifier eissn1528-896X
    keywordsFlow (Dynamics)
    keywordsPipelines
    keywordsUnderwater pipelines
    keywordsSeabed
    keywordsVortex shedding
    keywordsMechanisms
    keywordsPressure
    keywordsEngineering simulation
    keywordsBoundary layers
    keywordsCylinders
    keywordsReynolds number
    keywordsSediments
    keywordsThickness AND Turbulence
    treeJournal of Offshore Mechanics and Arctic Engineering:;2012:;volume( 134 ):;issue: 002
    contenttypeFulltext
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