Numerical Simulation of Flow-Induced Forces on Subsea Structures in a Group Under Uniform and Sheared Flow

Annapeh, Henry Francis; Kurushina, Victoria

doi:10.1007/978-3-031-15758-5_52

Cited by 3 publications

(3 citation statements)

References 28 publications

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“…Distance variations and corresponding case (arrangement) numbers are given in Table 1, where Case 1 is the base case, Cases 1-5 form the first series, Cases 1, 6-9 form the second series and the third series is consistent with distances in Case 1. The planar linear and parabolic sheared flows in this work, following the previous research in this direction [30,31], are defined using velocity profiles 𝑈, depending on the velocity 𝑈 , consistent with the Reynolds number of 3900 at the centreline of the computational domain. The definition of the linear velocity profile is as follows: The parametric studies are performed for the spacing ratios L/D, with respect to the squared cylinder size of D, in the bandwidth from 0.6 to 1.0.…”

Section: Numerical Modelmentioning

confidence: 99%

“…The current work continues the branch of numerical simulation studies performed for a group of three-four structures while placed in a planar sheared flow. Previous research in this direction considers circular structures: two objects of a different size [30] in the uniform flow, a group of three small structures in several arrangements [31] and a group of small structures in a triangular layout in proximity to a larger object [32] in both uniform and sheared flows. A large group of structures of different cross-sections is considered in [33], where the D-shape, previously implemented in [34], is found to have a positive effect on the reduction of fluid loads.…”

Section: Introductionmentioning

confidence: 99%

“…The current study investigates smaller structures with two distinct cross-sectional shapes: circular and half-circular. These smaller cylinders are placed in proximity to a larger squared structure, following the results in [31]. The arrangement leads to a superposition of generated vortex streets, and the aim of this investigation is to identify scenarios of reduced hydrodynamic loads for the considered range of cases, which would be a practical choice of the structural layout.…”

Section: Introductionmentioning

confidence: 99%

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Flow-Induced Forces for a Group of One Large and Several Small Structures in the Sheared Turbulent Flow

Annapeh

Kurushina

2023

Fluids

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Evaluating the hydrodynamic force fluctuations acting on each structure in a group of subsea objects of different cross-section shapes, sizes and relative positions represents a challenge due to the sensitivity of the vortex shedding process, especially for a variety of sheared flows. The present study uses the numerical 2D computational fluid dynamics model to estimate the flow-induced forces on a group of small circular and D-shaped cylinders in the linear and parabolic sheared flow, which are placed in proximity to a larger structure of the squared cross-section. This allows us to evaluate loads, which are affected by the presence of subsea equipment located on the seabed. The average Reynolds number of the considered linear flow profile is 3900, while the parabolic flow profile has the maximum Reynolds number of 3900. The k-ω SST turbulence model is used for simulations. The work demonstrates the effect of the cross-sectional shape of smaller cylinders on hydrodynamic coefficients, explores the effect from the spacing in between the structures and highlights differences between loads in the linearly sheared and parabolic flow. The results obtained show that the presence of the squared cylinder notably influences the mean drag coefficient on the first cylinder, for both circular and D-shaped cylinders. The parabolic sheared flow profile in this series leads to the highest mean drag and the highest amplitudes of the fluctuating drag and lift coefficients.

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Section: Numerical Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Flow-Induced Forces for a Group of One Large and Several Small Structures in the Sheared Turbulent Flow

Annapeh

Kurushina

2023

Fluids

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Analysis of the Drag-Reduction Ability of the Layout and Cross-Sectional Shapes of Subsea Structures in the Critical Flow Mode

Annapeh,

Kurushina

2024

Vestnik Donskogo gosudarstvennogo tehničeskogo universiteta

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Introduction. Slender structures of subsea energy production systems are under constant influence of currents and waves. Hydrodynamic loads result from the interaction of subsea pipelines, umbilicals, equipment supports with fluid flows, and lead to the vortex formation in the area behind the structures. Vortex-induced forces are the sources of the cyclic loading. They accelerate gradually the fatigue damage, which may result in a failure. One of the ways to reduce the loads on subsea structures is to alter the shape of a cross-section, taking into account the flow regime. Dependence of the resulting hydrodynamic loads on the cross-sectional shape and relative position of structures has not been studied in details for the uniform flow in the critical mode. The current work is aimed at filling this gap. The research objective is to consider the impact of the distance between the structures, and also, the presence of a D-shaped structure, placed upstream relative to the group of three cylinders of different cross-sectional shapes.Materials and Methods. The computational fluid dynamics approach was used in this work for numerical simulations of vortex-induced forces in the ANSYS Fluent software for cylinder with D = 0.3 m. Modelling was conducted with the Detached Eddy Simulation (DES) method, which combined advantages of the Reynolds-averaged Navier-Stokes equation (RANS) method and the Large Eddy Simulation (LES) method. The object of the research was the system of four structures in the 2D computational domain, which included the upstream D-shaped cylinder and the main group of three cylinders with the circular, squared and diamond shapes of the cross-section. The transient process was considered, where structures were under the influence of the uniform flow in the critical regime at Re = 2.5×10⁵.Results. Five sets of data were obtained in simulations for the time-dependent coefficients of the lift and drag forces: for the main system — of the D-shaped, circular, square and diamond structures, and also for the four systems — of only D-shaped, only circular, only square and only diamond shaped structures. Additional analysis was conducted for the effect of the distance between the structures on the amplitude of fluctuating hydrodynamic force coefficients. The obtained results are presented as time histories of coefficients of the lift and drag forces, frequency analysis and contours of velocity, pressure and vorticity fields. The results indicate a positive effect of the upstream D-shaped structure on reducing the drag force, acting on the central structure in the group of three cylinders located downstream.Discussion and Conclusion. The results of the performed studies facilitate the informed decisions regarding the arrangement of subsea structures in a group of four objects, depending on the cross-sectional shape and the distance between the structures. The upstream D-shaped structure provides reducing the hydrodynamic drag force acting on the central structure in the downstream group of three structures, thereby slowing the fatigue accumulation and increasing the time of safe operation.

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Transversal Vortex-Induced Vibration of a Circular Cylinder in Tandem with a Stationary Square Structure

Annapeh,

Kurushina

2024

Applied Mechanics

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This paper considers a system with two offshore structures in tandem, where the upstream square structure is fixed and the downstream circular structure has one degree of freedom. Cylinders are subject to uniform and linearly sheared flow conditions. The dynamics of the downstream structure are investigated by using a computational fluid dynamics approach for a Reynolds number range of 1000–6500 at the centerline. The spacing ratio for the tandem structures is L/D = 6 in this work, corresponding to the wake interference regime. The effect of the shear parameter on the development of vortex-induced vibrations in the lock-in state within the downstream structure is studied, in comparison with the lock-in of an isolated circular structure. The results of this research include statistics on the displacement amplitude, drag and lift coefficients, frequency ratio, time histories and contours of vorticity. The results obtained show the maximum displacement amplitude of the isolated structure in a uniform flow at the level of 0.8 diameters during the upper branch. The investigation also shows a later development in the maximum displacement during the upper branch of the downstream structure under shear flow conditions, with the highest maximum displacement of 1.18 diameters seen for the shear parameter of 0.05.

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Numerical Simulation of Flow-Induced Forces on Subsea Structures in a Group Under Uniform and Sheared Flow

Cited by 3 publications

References 28 publications

Flow-Induced Forces for a Group of One Large and Several Small Structures in the Sheared Turbulent Flow

Flow-Induced Forces for a Group of One Large and Several Small Structures in the Sheared Turbulent Flow

Analysis of the Drag-Reduction Ability of the Layout and Cross-Sectional Shapes of Subsea Structures in the Critical Flow Mode

Transversal Vortex-Induced Vibration of a Circular Cylinder in Tandem with a Stationary Square Structure

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