Nonlinear Effects on Long-Term Distributions of Wave-Induced Loads for Tankers

1998 ◽  
Vol 120 (2) ◽  
pp. 65-70 ◽  
Author(s):  
C. Guedes Soares ◽  
T. E. Schellin
Keyword(s):  
Nonlinear Wave ◽  
Nonlinear Effect ◽  
Nonlinear Effects ◽  
Vertical Load ◽  
Load Effects ◽  
Wave Induced

A method of long-term formulation of the nonlinear wave-induced vertical load effects on ships was applied to three tanker hulls of different sizes. For large tanker hulls, the nonlinear effect is not significant, and thus linear theories can continue to be used for earlier studies on these kind of ships, contrary to what was shown earlier for containership hulls. However, for smaller tankers, significant nonlinear values were obtained, with both sagging and hogging nonlinear results being larger than the linear ones.

Abnormal Wave-Induced Load Effects in Ship Structures

2008 ◽  
Vol 52 (01) ◽  
pp. 30-44 ◽  
Author(s):  
C. Guedes Soares ◽  
N. Fonseca ◽  
R. Pascoal
Keyword(s):  
Extreme Values ◽  
Time History ◽  
Design Criterion ◽  
Freak Waves ◽  
Reference Design ◽  
Load Effects ◽  
Central North Sea ◽  
Wave Induced ◽  
First Time

The paper presents an approach to determine the global load effects induced on shif structures by abnormal, freak, or episodic waves. It refers to the present procedure of determining extreme values of wave-induced responses, including the recent advances of adopting time series of wave elevation as reference design conditions t calculate the wave-induced structural loads on ships in heavy weather. It is show how this procedure can be extended to account for abnormal or episodic waves Reference is made to what is presently known about abnormal or freak waves showing that although it is possible to determine the loads induced by these wave in floating and fixed structures, the present knowledge about the probability of occurrence of these waves is not enough to allow a wave design criterion to be defined in a way consistent with the present probabilistic approaches. However, it is suggested that at the present stage of knowledge it is possible to determine the load induced by abnormal waves similar to ones that have been measured at various ocean locations and that are thus realistic; a method is described to perform such calculations. Although this information cannot replace the wave-induced loads calculated with the presently established procedures, it can serve as guidance for th design. An application example is presented of a containership subjected to a wav trace that includes an episodic wave that was measured during a severe storm in Central North Sea. The measured wave time history is modified in order to investigate the influence of the wave steepness on the induced vertical motions and loads. Th loads induced by the abnormal wave are compared for the first time with extreme values from long-term distributions.

A TECHNIQUE OF PANELS CUTTING FOR MODIFICATION OF HULL GEOMETRY HYDRODYNAMIC MODELS

2021 ◽  
Vol 162 (A2) ◽  
Author(s):  
H Jafaryeganeh ◽  
C Guedes Soares
Keyword(s):  
Case Studies ◽  
The Body ◽  
Vertical Shear ◽  
Vertical Load ◽  
Load Prediction ◽  
Shear Forces ◽  
Hydrodynamic Models ◽  
Initial Mesh ◽  
Load Effects ◽  
Wave Induced

A panel cutting technique is developed for automatic modification of an initial mesh of a ship hull used for hydrodynamic computations leading to improved meshes for the prediction of wave induced vertical load effects. The technique can provide a model with divided panels in any defined position regardless of the initial discretization of the body. The applications of the provided technique include panel distinction and division in predetermined positions, generation of finer mesh based on the initial coarser model of meshes and improvement of vertical load prediction in predetermined positions. The method is applied for case studies of a barge, shuttle tanker and frigate to depict various applications. Finally, the hydrostatic and hydrodynamic vertical shear forces are calculated for two models of initial and modified panels of well-known frigate 5415. The results are compared for the sections alongside the ship and accuracy of load integration is shown for predetermined sections.

A Technique of Panels Cutting for Modification of Hull Geometry Hydrodynamic Models

2020 ◽  
Vol 162 (A2) ◽  
Author(s):  
H Jafaryeganeh ◽  
C Guedes Soares
Keyword(s):  
Case Studies ◽  
The Body ◽  
Vertical Shear ◽  
Vertical Load ◽  
Load Prediction ◽  
Shear Forces ◽  
Hydrodynamic Models ◽  
Initial Mesh ◽  
Load Effects ◽  
Wave Induced

A panel cutting technique is developed for automatic modification of an initial mesh of a ship hull used for hydrodynamic computations leading to improved meshes for the prediction of wave induced vertical load effects. The technique can provide a model with divided panels in any defined position regardless of the initial discretization of the body. The applications of the provided technique include panel distinction and division in predetermined positions, generation of finer mesh based on the initial coarser model of meshes and improvement of vertical load prediction in predetermined positions. The method is applied for case studies of a barge, shuttle tanker and frigate to depict various applications. Finally, the hydrostatic and hydrodynamic vertical shear forces are calculated for two models of initial and modified panels of well-known frigate 5415. The results are compared for is shown for predetermined sections.

scholarly journals A cosmic microscope for the preheating era

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
JiJi Fan ◽  
Zhong-Zhi Xianyu
Keyword(s):  
Scalar Field ◽  
Nonlinear Effect ◽  
Large Scale ◽  
Nonlinear Effects ◽  
Light Fields ◽  
Unique Probe ◽  
Light Scalar ◽  
Spatially Varying ◽  
Near Future ◽  
Scalar Perturbations

Abstract Light fields with spatially varying backgrounds can modulate cosmic preheating, and imprint the nonlinear effects of preheating dynamics at tiny scales on large scale fluctuations. This provides us a unique probe into the preheating era which we dub the “cosmic microscope”. We identify a distinctive effect of preheating on scalar perturbations that turns the Gaussian primordial fluctuations of a light scalar field into square waves, like a diode. The effect manifests itself as local non-Gaussianity. We present a model, “modulated partial preheating”, where this nonlinear effect is consistent with current observations and can be reached by near future cosmic probes.

Resonant reflection of surface water waves by periodic sandbars

1985 ◽  
Vol 152 ◽  
pp. 315-335 ◽  
Author(s):  
Chiang C. Mei
Keyword(s):  
Water Waves ◽  
Resonance Condition ◽  
Nonlinear Effects ◽  
Sea Bottom ◽  
Strong Reflection ◽  
Weak Reflection ◽  
Surface Water Waves ◽  
Wave Induced ◽  
Incident Waves ◽  
Resonant Reflection

One of the possible mechanisms of forming offshore sandbars parallel to a coast is the wave-induced mass transport in the boundary layer near the sea bottom. For this mechanism to be effective, sufficient reflection must be present so that the waves are partially standing. The main part of this paper is to explain a theory that strong reflection can be induced by the sandbars themselves, once the so-called Bragg resonance condition is met. For constant mean depth and simple harmonic waves this resonance has been studied by Davies (1982), whose theory, is however, limited to weak reflection and fails at resonance. Comparison of the strong reflection theory with Heathershaw's (1982) experiments is made. Furthermore, if the incident waves are slightly detuned or slowly modulated in time, the scattering process is found to depend critically on whether the modulational frequency lies above or below a threshold frequency. The effects of mean beach slope are also studied. In addition, it is found for periodically modulated wave groups that nonlinear effects can radiate long waves over the bars far beyond the reach of the short waves themselves. Finally it is argued that the breakpoint bar of ordinary size formed by plunging breakers can provide enough reflection to initiate the first few bars, thereby setting the stage for resonant reflection for more bars.

A First Step Towards the Development of a Pipeline Wrinkle Material Ultimate Limit State

2006 ◽  
Author(s):  
Aaron Dinovitzer ◽  
Sanjay Tiku ◽  
Vlado Semiga ◽  
Abdelfettah Fredj ◽  
Joe Zhou ◽  
...  
Keyword(s):  
Limit State ◽  
Low Frequency ◽  
Failure Criteria ◽  
Ultimate Limit State ◽  
Ongoing Research ◽  
Undesirable Event ◽  
Load Effects ◽  
Line Pressure ◽  
Fault Displacement

While the formation of a wrinkle in an onshore pipeline is an undesirable event, in many instances this event does not have immediate pipeline integrity implications. The magnitude or severity of a wrinkle formed due to displacement controlled loading processes (e.g. slope movement, fault displacement, frost heave and thaw settlement) may increase with time, eventually causing serviceability concerns (e.g. fluid flow or inspection restrictions). Pipe wall damage leading to cracking and eventually a loss of containment involves contributions from the wrinkle formation and growth processes, as well as, wrinkle deformations promoted by in-service line pressure, temperature and seasonal soil displacements. The objective of this paper is to provide an overview of the ongoing research efforts, sponsored by TransCanada PipeLines Ltd. and Tokyo Gas Co. Ltd., towards the development of a mechanics based wrinkle ultimate limits state that may be used in future to evaluate the long term integrity of wrinkled pipeline segments. The research efforts include non-linear finite element modeling to demonstrate the ability of experimentally derived material properties to predict the formation of through wall cracking induced by high and low frequency load effects. This paper outlines the material testing program used to support the development of failure criteria capable of considering the contributions of monotonic deformation, as well as, high and low cycle cyclic loading.

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