A Method to Quantify Mitigation Characteristics of Shock Isolation Seats Before Installation in a High-Speed Planing Craft

2015 ◽  
Author(s):  
Michael R. Riley ◽  
Timothy W. Coats ◽  
Heidi P. Murphy ◽  
Neil Ganey
Keyword(s):  
High Speed ◽  
Historical Perspective ◽  
Lessons Learned ◽  
Computational Method ◽  
Impact Loads ◽  
Wave Impact ◽  
New Approach ◽  
Planing Craft ◽  
Acceleration Data ◽  
Shock Isolation

This paper presents a new approach for quantifying the mitigation achieved by a passive marine shock isolation seat. A brief historical perspective is summarized to explain why common myths have evolved that has led to seats being integrated into craft only to find out during subsequent seakeeping trials that the seats provide little to no mitigation or that they actually amplify wave impact loads. Acceleration data is presented to demonstrate use of the new computational method and the lessons learned are explained in terms that support development of a standard for laboratory seat testing.

Lessons Learned from Full-Scale Seakeeping Trial Acceleration Data for HighSpeed Planing Craft and Implications for Scale Model Testing

2017 ◽  
Author(s):  
Michael R. Riley ◽  
Timothy Coats
Keyword(s):  
High Speed ◽  
Impact Load ◽  
Maximum Load ◽  
Model Testing ◽  
Full Scale ◽  
Lessons Learned ◽  
Scale Model ◽  
Wave Impact ◽  
Acceleration Data ◽  
Hull Structure

This paper summarizes lessons learned from analyzing acceleration data recorded during full-scale seakeeping trials of high speed craft. Applications using a consistent maximum wave impact load approach in different areas of interest, including hull structure, shock isolation seat evaluation, and equipment ruggedness criteria are presented. The lessons learned and the maximum load applications suggest that there are implications for scale model testing and computational fluid dynamics.

Coupled Fluid-Structural Modelling to Predict Wave Impact Loads on High-Speed Planing Craft

2001 ◽  
Author(s):  
Simon Rees ◽  
◽  
David Reed ◽  
Colin Cain ◽  
Bob Cripps ◽  
...  
Keyword(s):  
High Speed ◽  
Impact Loads ◽  
Structural Modelling ◽  
Wave Impact ◽  
Planing Craft

scholarly journals An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 2: Mitigation of Wave Impact Loads

2017 ◽  
Vol 61 (2) ◽  
pp. 51-63 ◽  
Author(s):  
Javad AlaviMehr ◽  
Jason Lavroff ◽  
Michael R. Davis ◽  
Damien S. Holloway ◽  
Giles A. Thomas
Keyword(s):  
Experimental Investigation ◽  
High Speed ◽  
Control Algorithms ◽  
Impact Loads ◽  
Wave Impact ◽  
Ride Control

Impact Loads From Drop Test of a Circular Section With 42 Force Transducers

2015 ◽  
Author(s):  
Gunnar Lian ◽  
Ole David Økland ◽  
Tone M. Vestbøstad
Keyword(s):  
Model Test ◽  
Large Volume ◽  
High Speed ◽  
Limit State ◽  
Ultimate Limit State ◽  
Impact Loads ◽  
Wave Impact ◽  
Circular Section ◽  
Force Transducers ◽  
Drop Tests

Results from previous model test campaigns of various large-volume platforms indicate that wave impact loads on vertical platform columns can become high in extreme sea states. Moreover, column slamming is a highly non-linear and complex problem and reliable estimation of Ultimate Limit State (ULS) and Accidental Limit State (ALS) design loads is a challenge. A model test campaign dedicated to investigate column slamming has been performed on a large volume platform at Marintek. Special effort was put into designing a model and instrumentation package that could capture the complex phenomenon of slamming due to breaking or near breaking waves as accurately as possible. As part of the validation of the instrumentation for this test, drop tests were performed on a circular section with 42 force transducers. In the model test, this section was mounted on one of the platform columns for measuring wave impacts. In the present drop tests, the same section was dropped in still water in a small basin. Different impact velocities and impact angles were investigated. High-speed video recordings were also used to document the tests. This paper presents the setup used in the drop tests. The results from the drop tests are discussed and compared to theoretical solutions.

A Dynamic Simulation of Wave Impact Loads on Offshore Floating Platforms

1976 ◽  
Vol 98 (2) ◽  
pp. 550-557
Author(s):  
J. G. Giannotti
Keyword(s):  
Structural Analysis ◽  
High Speed ◽  
Degrees Of Freedom ◽  
Impulsive Loading ◽  
Impact Loads ◽  
Offshore Platforms ◽  
Wave Impact ◽  
Six Degrees Of Freedom ◽  
Marine Vehicles ◽  
Floating Platforms

Some of the most critical loads to consider in developing design criteria for offshore platforms are those caused by wave hydrodynamic impact. The effect of these loads can be of a local nature in the form of plating damage as a result of impulsive loading, or it can be felt on the overall structure in the form of induced vibration, and increased bending moments and shears. Traditionally, the prediction of these loads has been highly empirical and designers have had to rely heavily on conservative factors of safety in order to account for the lack of confidence in these predictions. The current degree of sophistication of advanced techniques of structural analysis such as the finite element method has not been matched by equally sophisticated loads prediction methods. Consequently, the advantages offered by the computerized structural analysis schemes are considerably reduced due to the unacceptable load inputs. This paper fills part of this void by presenting an analytical model for predicting wave impact loads for the design of offshore platforms. The method is based on the Payne Impact Program which has been used before for predicting impact pressures and loads acting on high speed marine vehicles. The model simulates six-degrees-of-freedom and allows impacts at any wave heading. As inputs it requires geometric information, sea state definition, and a description of the relative motion of platform and wave. It is particularly suited to allow analysis of the results in probabilistic form, so that the severity and frequency of occurrence of impacts can be predicted.

Wave Impact Loads Prediction With Compressible Air Effects Using CFD

2019 ◽  
Author(s):  
I. Gatin ◽  
S. Liu ◽  
N. Vladimir ◽  
H. Jasak
Keyword(s):  
Vertical Wall ◽  
Wave Theory ◽  
Ideal Gas ◽  
Computational Method ◽  
Green Water ◽  
Impact Loads ◽  
Wave Impact ◽  
Trapped Air ◽  
Air Pockets ◽  
Air Compression

Abstract A computational method for predicting wave impact loads where compressible air effects might be present is presented in this paper. The method is a Finite Volume based Computational Fluid Dynamics method where air is modelled as a compressible ideal gas while water is treated as incompressible. Special numerical treatment of the interface based on the Ghost Fluid Method enables capturing the sharp transition in compressible properties of air and water across the free surface, making the method accurate for predicting trapped air pockets during wave impacts or slamming. The approach enables predicting impacts where trapped air pockets play an important role in the loading of the structure due to the capacity to absorb and redistribute wave impact energy. The present approach is validated on a falling water slamming case where trapped air compression is present. Next, a full scale wave breaking impact on a vertical wall is simulated and the results compared to experimental measurements, with trapped air compression effects. Finally, the method is applied on a breakwater green water loading calculation of an Ultra Large Container Ship in an extreme focused wave impact based on the Response Conditioned Wave theory. Motion of the container vessel is calculated directly during the simulation. The calculation is shown to be computed with limited computer resources in reasonable amount of time. Overall the approach proved to be accurate, robust and efficient, providing a tool for assessing wave impact loads with or without compressible air effects.

scholarly journals An Experimental Investigation of Ride Control Algorithms for High-Speed Catamarans Part 2: Mitigation of Wave Impact Loads

2017 ◽  
Vol 61 (02) ◽  
pp. 51-63
Author(s):  
Javad AlaviMehr ◽  
Jason Lavroff ◽  
Michael R. Davis ◽  
Damien S. Holloway ◽  
Giles A. Thomas
Keyword(s):  
Control System ◽  
High Speed ◽  
Control Algorithms ◽  
Impact Loads ◽  
Wave Impact ◽  
Pitch Control ◽  
Model Scale ◽  
Ride Control ◽  
Control Feedback ◽  
Ride Control System

High-speed craft frequently experience large wave impact loads due to their large motions and accelerations. One solution to reduce the severity of motion and impact loadings is the installation of ride control systems. Part 1 of this study investigates the influence of control algorithms on the motions of a 112-m highspeed catamaran using a 2.5-m model fitted with a ride control system. The present study extends this to investigate the influence of control algorithms on the loads and internal forces acting on a hydroelastic segmented catamaran model. As in Part 1, the model active control system consisted of a center bow T-Foil and two stern tabs. Six motion control feedback algorithms were used to activate the model-scale ride control system and surfaces in a closed loop system: local motion, heave, and pitch control, each in a linear and nonlinear application. The loads were further determined with a passive ride control system and without control surfaces fitted for direct comparison. The model was segmented into seven parts, connected by flexible links that replicate the first two natural frequencies and mode shapes of the 112-m INCAT vessel, enabling isolation and measurement of a center bow force and bending moments at two cross sections along the demi-hulls. The model was tested in regular head seas at different wave heights and frequencies. From these tests, it was found that the pitch control mode was most effective and in 60-mm model-scale waves it significantly reduced the peak slam force by 90% and the average slam induced bending moment by 75% when compared with a bare hull without ride controls fitted. This clearly demonstrates the effectiveness of a ride control system in reducing wave impact loads acting on high-speed catamaran vessels.

Yaw Galloping of a TLWP Platform Under High Speed Currents by Analytical Methods and its Comparison With Experimental Results

2017 ◽  
Author(s):  
Francisco Lamas ◽  
Miguel A. M. Ramirez ◽  
Antonio Carlos Fernandes
Keyword(s):  
High Speed ◽  
Production Systems ◽  
Experimental Tests ◽  
Experimental Results ◽  
Analytical Methodology ◽  
New Approach ◽  
Laboratory Facilities ◽  
Polynomial Curve ◽  
Computational Fluid Dynamics Cfd ◽  
Cfd Analyses

Flow Induced Motions are always an important subject during both design and operational phases of an offshore platform life. These motions could significantly affect the performance of the platform, including its mooring and oil production systems. These kind of analyses are performed using basically two different approaches: experimental tests with reduced models and, more recently, with Computational Fluid Dynamics (CFD) dynamic analysis. The main objective of this work is to present a new approach, based on an analytical methodology using static CFD analyses to estimate the response on yaw motions of a Tension Leg Wellhead Platform on one of the several types of motions that can be classified as flow-induced motions, known as galloping. The first step is to review the equations that govern the yaw motions of an ocean platform when subjected to currents from different angles of attack. The yaw moment coefficients will be obtained using CFD steady-state analysis, on which the yaw moments will be calculated for several angles of attack, placed around the central angle where the analysis is being carried out. Having the force coefficients plotted against the angle values, we can adjust a polynomial curve around each analysis point in order to evaluate the amplitude of the yaw motion using a limit cycle approach. Other properties of the system which are flow-dependent, such as damping and added mass, will also be estimated using CFD. The last part of this work consists in comparing the analytical results with experimental results obtained at the LOC/COPPE-UFRJ laboratory facilities.

scholarly journals Why Protect Ancient Woodland in the UK? Rethinking the Ecosystem Approach

2020 ◽  
pp. 1-24
Author(s):  
Jona Razzaque ◽  
Claire Lester
Keyword(s):  
High Speed ◽  
Biodiversity Loss ◽  
Ecosystem Approach ◽  
Lessons Learned ◽  
Value Systems ◽  
Ancient Woodland ◽  
Forestry Practices ◽  
Regulatory Frameworks ◽  
Trade Offs ◽  
The Uk

Abstract Sites of ancient woodland in the United Kingdom (UK) are diminishing rapidly and the multifunctional forest management system with its fragmented approach fails effectively to protect such woodland. In the face of reports on the destruction of ancient woodland, the HS2 High-Speed train project in the UK signifies the extent of trade-offs among the key stakeholders. Such large infrastructure projects typically come with high environmental and social costs, including deforestation, habitat fragmentation, biodiversity loss, and social disruption. This article examines the protection of ancient woodland in the UK and assesses the challenges in applying the ecosystem approach, an internationally recognized sustainability strategy, in the context of such protection. A better understanding of the ecosystem approach to manage ancient woodland is critical for promoting sustainable forestry practices in the UK and informs the discussion in this article of the importance of conserving ancient woodland globally. Lessons learned from UK woodland policies and certification schemes include the need to have in place strong regulatory frameworks, introduce clear indicators, and recognize pluralistic value systems alongside economic considerations. The article concludes that the protection of ancient woodland in the UK requires distinct and strong laws that reflect multiple values of this resource, acknowledge the trade-offs among stakeholders, and adopt an inclusive approach to reduce power asymmetries.

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