A higher order time domain panel method for linear and weakly non linear seakeeping problems.

This paper presents a higher order time domain boundary elements method based on the Rankine sources for the computation of both linear and weakly non-linear effects for both fixed and free floating bodies. The geometry is described based on surfaces in a standard iges file, considering a NURBS (Non Uniform Rational Basis-Spline) description. The potential function, velocity, free-surface elevation and other quantities are defined using b-splines of arbitrary degree and the floating body interaction is solved using the potential acceleration approach on a Runge-Kutta scheme for time evolution. The integral equation is obtained and solved considering several possibilities for the collocation points, leading to an over-determined system. The integration over the panels is performed using a mixed desingularized-numerical method over Gaussian points. The results comparison are performed with WAMIT solution for a floating sphere concerning wave runup, body motions, velocity field, mean drift components in time domain.

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A 3D Higher Order Time Domain Rankine Panel Method for Wave-Current Interaction

Volume 7: Ocean Engineering ◽

10.1115/omae2016-54994 ◽

2016 ◽

Author(s):

Felipe Ruggeri ◽

Rafael A. Watai ◽

Alexandre N. Simos

Keyword(s):

Time Domain ◽

Higher Order ◽

Second Order ◽

Panel Method ◽

Order Effects ◽

Rankine Panel Method ◽

Wave Drift Damping ◽

Current Interaction ◽

Order Quantities ◽

The University

The wave-current effects are very important in several offshore applications, for instance, the wave-drift-damping of a Turret moored FPSO. This papers presents the incorporation of current effects in the higher order time domain Rankine Panel Method on development in the Numerical Offshore Tank (TPN) at the University of São Paulo (USP) already introduced in [1]. The method is based on a perturbation theory to study first and second order effects, considering the geometry described using NURBS (Non Uniform Rational Basis Spline) and the potential function, free surface elevation, pressure etc by B-splines of arbitrary degree. The study is performed for a simplified geometry (sphere) and the results regarding a fixed hemisphere compared to other numerical methods considering both first and second order quantities are presented.

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Geometrically Non-Linear Analysis of Doubly Curved Laminated and Sandwich Fibre Reinforced Composite Shells with a Higher Order Theory and C° Finite Elements

Journal of Reinforced Plastics and Composites ◽

10.1177/073168449201100905 ◽

1992 ◽

Vol 11 (9) ◽

pp. 1048-1076 ◽

Cited By ~ 17

Author(s):

T. Kant ◽

J.R. Kommineni

Keyword(s):

Finite Elements ◽

Order Theory ◽

Linear Analysis ◽

Higher Order ◽

Composite Shells ◽

Reinforced Composite ◽

Non Linear ◽

Higher Order Theory ◽

Doubly Curved

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Prediction of deepwater riser VIV with an improved time domain model including non-linear structural behavior

Ocean Engineering ◽

10.1016/j.oceaneng.2021.109508 ◽

2021 ◽

Vol 236 ◽

pp. 109508

Author(s):

Sang Woo Kim ◽

Svein Sævik ◽

Jie Wu ◽

Bernt Johan Leira

Keyword(s):

Time Domain ◽

Domain Model ◽

Structural Behavior ◽

Non Linear ◽

Deepwater Riser

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Concrete Modeling for Extreme Wave Slam Events

Volume 3A: Structures, Safety and Reliability ◽

10.1115/omae2017-61331 ◽

2017 ◽

Author(s):

Kasper Wåsjø ◽

Terje P. Stavang ◽

Tore H. Søreide

Keyword(s):

Time Domain ◽

Linear Time ◽

Limit State ◽

Material Model ◽

Time Domain Analysis ◽

Domain Analysis ◽

Capacity Control ◽

Extreme Wave ◽

Conventional Design ◽

Non Linear

Experience from model tests has initiated a growing attention towards extreme wave slam as a critical load situation for offshore large volume structures. Most of the problem is related to the local slam pressure, which may go up to several MPa’s for 100-year and 10 000-year waves. The paper deals with modeling techniques for marine concrete structures under extreme slam loading from waves where dynamic effects together with material softening play a major role for the response. Different analysis approaches for ultimate limit state (ULS) and accidental limit state (ALS) controls are discussed in view of reliability philosophy as basis for conventional design approach. The present paper is devoted to the local impact scenario and the alternative approaches for response and capacity control involving non-linear time domain analyses. Conventional design schemes as based on linear elastic models for response calculation together with code specified capacity control often come out more conservative than non-linear approach. The paper demonstrates by case studies how softening of the structure in general reduces the response in terms of section forces. A key issue when going from conventional linear approaches into non-linear techniques is to still keep an acceptable reliability level on the capacity control. Load and material factors are normally based on structures with limited non-linearity where linear response modeling is representative. Implementing non-linear material model in time domain analysis has a major challenge in limiting the sensitivity in response and capacity calculation. The paper demonstrates the way material model of concrete affects the section forces to go into local capacity control, and concludes on needed sensitivity analyses. Practical approaches on the concrete slam problem together with resulting utilizations from the control are demonstrated. The full non-linear technique by response and capacity control in one analysis is also handled, using average material parameters and justifying safety factors for the effect of implementing characteristic lower strength of concrete in the capacity. The paper ends up in a recommendation on non-linear time domain analysis procedure for typically slam problems. A discussion is also given on applicable design codes with attention to non-linear analysis.

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