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Subrata K. Chakrabarti

Bio: Subrata K. Chakrabarti is an academic researcher. The author has contributed to research in topics: Inertia & Velocity potential. The author has an hindex of 1, co-authored 1 publications receiving 14 citations.

Papers
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TL;DR: In this article, the authors applied diffraction to Stokes' fifth order gravity wave theory to obtain an expression for the velocity potential in the cylindrical polar coordinate system, based on which the dynamic pressure at the surface of a vertical cylinder and the total horizontal force on the cylinder in the direction of the wave propagation were determined.
Abstract: The method of diffraction is applied to Stokes' fifth order gravity wave theory to obtain an expression for the velocity potential in the cylindrical polar coordinate system. Based on this expression, the dynamic pressure at the surface of a vertical cylinder and the total horizontal force on the cylinder in the direction of the wave propagation are determined. The wave force is written in an equivalent form of the inertial part of Morison's equation and the effective inertial coefficients are shown to be functions of a single dimensionless quantity. The different parameters involved are plotted or tabulated so that forces on a vertical cylinder due to a nonlinear wave up to fifth order may be easily evaluated. Correlation of the theory with the available experimental data was found to be reasonably good.

19 citations


Cited by
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TL;DR: In this paper , numerical investigations on a free-floating Catenary Anchor Leg Moorings (CALM) buoy were carried out and an Orcaflex-coupled model of the CALM buoy system with submarine hoses in Lazy-S configuration was presented.

26 citations

Journal ArticleDOI
TL;DR: In this article , the fluid-structure interaction (FSI) from wave diffraction forces on CALM buoys and cylindrical structures, based on the hydrodynamics with connections, was investigated.
Abstract: ABSTRACT This research fills the gap in understanding fluid–structure interaction (FSI) from wave diffraction forces on CALM buoys and cylindrical structures, based on the hydrodynamics with connections. Recently, there is an increased application of (un)loading marine hoses for Catenary Anchor Leg Moorings (CALM) buoy systems in the offshore industry due to the need for more flexible marine structures that are cost-saving, easier to install, and service. However, different operational issues challenge these hoses, like during hose disconnection. Also, the fluid behaviour was investigated based on the analytical and numerical models. The numerical modelling involves the boundary element method (BEM) and Orcaflex line theory. Hydrodynamic analysis is conducted on the disconnection-induced load response of marine bonded hoses during normal operation and accidental operation under irregular waves. A comparative study on hose performance during normal operation and accidental operation is also presented. Results of statistical analysis on CALM buoy system shows good motion characteristics.

20 citations

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TL;DR: In this article, the diffraction of a nonlinear nearly periodic wavetrain by a vertical circular cylinder is investigated using the multiple-scale perturbation method, where the envelope of the incident wavetrain is assumed to modulate slowly in the direction of wave propagation.
Abstract: Using the multiple-scale perturbation method, the diffraction of a nonlinear nearly periodic wavetrain by a vertical circular cylinder is investigated. The envelope of the incident wavetrain is assumed to modulate slowly in the direction of wave propagation. The relationship between the envelopes of incident and scattered waves is derived. It is shown that second-order scattered set-down waves propagate only at the long-wave velocity (gh)½. The formula for low-frequency wave forces acting on the cylinder is presented. The low-frequency wave forces, which are second-order quantities, are caused by set-down waves beneath the wavetrain and the results of the self-interactions of the leading-order first harmonic wave components. Numerical solutions are presented for the case where the wave envelope varies sinusoidally.

13 citations

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TL;DR: In this article , a numerical model was developed using a coupling method modeled by utilizing ANSYS AQWA and Orcaflex (Orcina Ltd., Ulverston, UK) dynamic models of the CALM buoy hoses.
Abstract: There is an increase in the utilization of the floating offshore structure (FOS) called Catenary Anchor Leg Mooring (CALM) buoys and the attached marine hoses due to the increasing demand for oil and gas products. These hoses are flexible and easier to use but have a short service life of about 25 years. They are adaptable in ocean locations of shallow, intermediate and deep waters. In this research, a numerical model was developed using a coupling method modeled by utilizing ANSYS AQWA and Orcaflex (Orcina Ltd., Ulverston, UK) dynamic models of the CALM buoy hoses. Two cases were comparatively studied: Lazy-S and Chinese-lantern configurations, under ocean waves and current. Comparisons were also made between coupled and uncoupled models. This research presents the hydrodynamic characteristics with a sensitivity analysis on the influence of waves, current attack angle, soil gradient, soil stiffness and environmental conditions that influence the performance of marine hoses. The study comparatively looked at the configurations from dynamic amplification factors (DAF) on marine hoses. The results show that marine hoses can be easily configured to suit the designer’s need, seabed soil type, seabed topography and the profiles that are useful for manufacturers. The sensitivity analysis also shows the effect of hose parameters on its hydrodynamic behavior from the wave–current interaction (WCI).

10 citations