Nonlinear analysis of submerged ocean buoy systems

Merchant, H. C.; Kelf, M.

doi:10.1109/oceans.1973.1161318

Cited by 6 publications

(7 citation statements)

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“…It was not in widespread use and not a candidate for cable system modeling. The LM representation matured over the next two decades [22], which naturally led to FEA concepts being applied to the cable dynamics problem [23]. As Ketchman and Lou [23] demonstrated, however, the LM methodology converges onto the same results as FEA representations as long as the discretization size is sufficiently small.…”

Section: Mooring Line Theoriesmentioning

confidence: 99%

“…The output vector is information passed back to the FAST glue code to advance to the next time-step sequence. In this application, the constraint variable, z, consists of the coefficients' cubic polynomial function, , in Equation (22). As a result, the constraints are .…”

Section: Figure 5: Inputs Outputs and Internal States For The Lm Momentioning

confidence: 99%

“…(36) The second state equations, the constraint equations, are those iterating on the constraint variables, z(t), to minimize a function. In this case, the functions minimized are those providing the solution to the cubic spline interpolation function in Equation (22). An example algorithm is given in [55].…”

Section: Equationsmentioning

confidence: 99%

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Extending the Capabilities of the Mooring Analysis Program: A Survey of Dynamic Mooring Line Theories for Integration Into FAST

Masciola

Jonkman

Robertson

2014

Volume 9A: Ocean Renewable Energy

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Techniques to model dynamic mooring lines take various forms. The most widely used models include a heuristic representation of the physics (such as a lumped-mass system), a finite-element analysis discretization of the lines (discretized in space), or a finite-difference model (which is discretized in both space and time). In this paper, the authors explore the features of the various models, weigh the advantages of each, and propose a plan for implementing one dynamic mooring line model into the open-source Mooring Analysis Program (MAP). MAP is currently used as a module for the FAST offshore wind turbine computer-aided engineering (CAE) tool to model mooring systems quasi-statically, although dynamic mooring capabilities are desired. Based on the exploration in this paper, the lumped-mass representation is selected for implementation in MAP based on its simplicity, low computational cost, and ability to provide physics similar to those captured by higher-order models. To begin, the underlying theories defining the three classes of dynamic mooring line models are identified and explored. This leads to insight into the capabilities of each representation. These capabilities are weighed against the current needs of the FAST wind turbine CAE tool, to which MAP will be coupled. Based on the assessment, a plan for integrating the dynamic mooring line theory into the current MAP structure is developed. Common problems arising from the determination of the model static equilibrium and known issues with numerical stability are addressed. Because MAP is a module that FAST can call, a plan consistent with the FAST modularization framework principles is described. Adding dynamic mooring line capabilities extends the features in MAP and also allows uncoupled analysis to be performed through MAP’s native Python bindings.

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Section: Mooring Line Theoriesmentioning

confidence: 99%

Section: Figure 5: Inputs Outputs and Internal States For The Lm Momentioning

confidence: 99%

See 1 more Smart Citation

Extending the Capabilities of the Mooring Analysis Program: A Survey of Dynamic Mooring Line Theories for Integration Into FAST

Masciola

Jonkman

Robertson

2014

Volume 9A: Ocean Renewable Energy

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“…In this study, a dynamic analysis of the proposed platform was performed through simulation before platform development. The existing studies mainly analyzed the motion between the ROV and the underwater cable while the USV was fixed or analyzed the motion changes of the underwater cable according to the USV motion at high speed [7][8][9][10][11][12][13], but, the unmanned ocean platform proposed in this study performs marine exploration while the USV and UUV move simultaneously. Therefore, it is necessary to analyze the effect of the underwater cable on the movement of the USV and UUV while the platform is moving.…”

Section: Introductionmentioning

confidence: 99%

Dynamics Modeling and Motion Simulation of USV/UUV with Linked Underwater Cable

Hong

Kim

2020

JMSE

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This paper describes a study on the dynamic modeling and the motion simulation of an unmanned ocean platform to overcome the limitations of existing unmanned ocean platforms for ocean exploration. The proposed unmanned ocean vehicle combines an unmanned surface vehicle and unmanned underwater vehicle with an underwater cable. This platform is connected by underwater cable, and the forces generated in each platform can influence each other’s dynamic motion. Therefore, before developing and operating an unmanned ocean platform, it is necessary to derive a dynamic equation and analyze dynamic behavior using it. In this paper, Newton’s second law and lumped-mass method are used to derive the equations of motion of unmanned surface vehicle, unmanned underwater vehicle, and underwater cable. As the underwater cable among the components of the unmanned ocean platform is expected to affect the motion of unmanned surface vehicle and unmanned underwater vehicle, the similarity of modeling is described by comparing with the cable modeling results and the experimental data. Finally, we constructed a dynamic simulator using Matlab and Simulink, and analyzed the dynamic behavior of the unmanned ocean platform through open-loop simulation.

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“…The discretized cable system presented in this paper is modeled using a lumped mass approach. This technique was developed heuristically as an extension of the finite element process and is based on a reorganization of the mass matrix (Walton and Polacheck 1960;Merchant and Kelf 1973). This simplification allows the dynamics problem to be computed more efficiently compared to strict finite element derivations, but without a significant compromise to accuracy (Ketchman and Lou 1975;Kamman and Huston 1999).…”

Section: Introductionmentioning

confidence: 99%

Static Analysis of the Lumped Mass Cable Model Using a Shooting Algorithm

Masciola

Nahon

Driscoll

2012

J. Waterway, Port, Coastal, Ocean Eng.

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This paper focuses on a method to solve the static configuration for a lumped mass cable system. The method demonstrated here is intended to be used prior to performing a dynamics simulation of the cable system. Conventional static analysis approaches resort to dynamics relaxation methods or root-finding algorithms (such as the Newton-Raphson method) to find the equilibrium profile. The alternative method demonstrated here is general enough for most cable configurations (slack or taut) and ranges of cable elasticity. The forces considered acting on the cable are due to elasticity, weight, buoyancy and hydrodynamics. For the three-dimensional problem, the initial cable profile is obtained from a set of two equations, regardless of the cable discretization resolution. Our analysis discusses regions and circumstances when failures in the method are encountered.

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Nonlinear analysis of submerged ocean buoy systems

Cited by 6 publications

References 0 publications

Extending the Capabilities of the Mooring Analysis Program: A Survey of Dynamic Mooring Line Theories for Integration Into FAST

Extending the Capabilities of the Mooring Analysis Program: A Survey of Dynamic Mooring Line Theories for Integration Into FAST

Dynamics Modeling and Motion Simulation of USV/UUV with Linked Underwater Cable

Static Analysis of the Lumped Mass Cable Model Using a Shooting Algorithm

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