scholarly journals Excessive Acceleration Criterion: Application to Naval Ships

2019 ◽  
Vol 7 (12) ◽  
pp. 431 ◽  
Author(s):  
Guido Boccadamo ◽  
Gennaro Rosano
Keyword(s):  
Failure Modes ◽  
Vertical Direction ◽  
Naval Research ◽  
Stability Criteria ◽  
Office Of Naval Research ◽  
Intact Stability ◽  
The Us ◽  
Ship Roll ◽  
Hull Forms ◽  
Level 2

In this paper, the application of the excessive acceleration (EA) criterion, one of five intact stability failure modes, within the second generation intact stability criteria (SGISC) framework, is shown for a set of naval vessels. First and second level vulnerability assessment of the criterion is applied to parent hulls D1 and D5 of D-Systematic Series, the US Office of Naval Research (ONR) Topside Series model, and the European multi-purpose frigate FREMM. All of which are semi-displacement, transom stern, and round bilge hull forms. Relatively low ship roll periods and great variations of hull geometry in vertical direction make this kind of ship potentially vulnerable to the EA phenomenon. Five displacements are considered for each vessel, and the minimum value of the KG height, which satisfies the Level 2 assessment, is computed for each of them. The curve of the minimum allowable KG is compared with the curve of the maximum KG complying with intact stability criteria specified in RINA (Registro Italiano Navale), classification rules for naval ships.

CHARACTERISTICS OF MOLTEN SALTS AND RECOMMENDATIONS FOR USE IN SOLAR POWER STATIONS

2016 ◽  
Vol 3 (1) ◽  
Author(s):  
Samaan G. Ladkany ◽  
William G. Culbreth ◽  
Nathan Loyd
Keyword(s):  
Molten Salt ◽  
Molten Salts ◽  
Solar Power ◽  
Weather Conditions ◽  
Thermal Capacity ◽  
Naval Research ◽  
Power Stations ◽  
Office Of Naval Research ◽  
The Us ◽  
Efficient Type

Molten salts (MS) in the 580°C range could be used to store excess energy from solar power stations and possibly from nuclear or coal. The energy can be stored up to a week in large containers at elevated temperature to generate eight hours of electricity to be used at night or during peak demand hours. This helps to reduce the fluctuation experienced at thermal solar power stations due to weather conditions. Our research supported by Office of Naval Research (ONR), presents a survey of salts to be used in molten salt technology. The physical characteristics of these salts such as density, melting temperature, viscosity, electric conductivity, surface tension, thermal capacity and cost are discussed. Cost is extremely important given the large volumes of salt required for energy storage at a commercial power station. Formulas are presented showing the amount of salt needed per required megawatts of stored energy depending on the type of salt. The estimated cost and the size of tanks required and the operating temperatures are presented. Recommendations are made regarding the most efficient type of molten salt to use. Commercial thermal solar power stations have been constructed in the US and overseas mainly in Spain for which molten salt is being considered. A field of flat mirrors together with collection towers are used in some designs and parabolic troughs used in others.

Influence of Systematic Hull Shape Variations on Ship Stability Performances in Waves

2020 ◽  
pp. 1-14
Author(s):  
Nicola Petacco ◽  
Giuliano Vernengo ◽  
Diego Villa ◽  
Antonio Coppedé ◽  
Paola Gualeni
Keyword(s):  
Second Generation ◽  
Design Space ◽  
Failure Modes ◽  
Free Form ◽  
Stability Criteria ◽  
Ship Stability ◽  
Parametric Roll ◽  
Modern Approach ◽  
Intact Stability ◽  
Geometric Variation

The sensitivity of ship stability performance in waves to geometric variation has been investigated by means of a simulation-based design framework. The study was devoted to assess the influence of hull geometry variations on some stability failure modes, namely, parametric roll (PR) and pure loss of stability (PLS). The application has been developed by using a representative model of a postpanamax container vessel. PR and PLS phenomena have been investigated by the application of second-generation intact stability criteria (SGISc). The initial multidimensional design space has been filled by 500 design configurations identified by means of a design of experiments approach. A method developed in-house, combining the subdivision surface and free-form deformation approaches, has been used to create the whole set of design alternatives. The generated design configurations have been assessed analyzing the results derived from application of the first- and the second-level SGIS vulnerability criteria for both the selected stability failure modes. To strengthen the correlation behaviors, the design space has then been further explored by using 10k design configurations exploiting the capabilities of a surrogate model-based approximation, relying on a Gaussian process formulation. The study has been focused on the correlations among the variables and the response functions, i.e., the outcomes of the SGIS vulnerability criteria. The significance, in terms of effects, of each geometry shape variable has been investigated. Results have been discussed in the light of the SGISc structure, to provide further insight into this innovative safety framework for a modern approach to intact stability. 1. Introduction In the last 10 years, the development of the so-called second-generation intact stability criteria (SGISc) has been one of the most engaging topics addressed by the Sub-Committee on Safety Design and Construction (SDC) of the International Maritime Organization (IMO).

Investigation of the 2nd Generation of Intact Stability Criteria for Ships Vulnerable to Parametric Rolling in Following Seas

2013 ◽  
Author(s):  
Stefan Krüger ◽  
Hannes Hatecke ◽  
Heike Billerbeck ◽  
Anna Bruns ◽  
Florian Kluwe
Keyword(s):  
Dynamic Stability ◽  
Direct Calculation ◽  
Stability Criteria ◽  
Parametric Rolling ◽  
Following Seas ◽  
2Nd Generation ◽  
Direct Assessment ◽  
Intact Stability ◽  
New Criteria ◽  
Level 2

The existing IMO intact stability criteria (IS-Code 2008) do not generally provide sufficient safety against dynamic stability failures such as parametric rolling for modern ships. Therefore, new stability criteria have been developed by IMO / SLF. These so-called Second Generation Stability Criteria shall ensure sufficient dynamic stability. The criteria are structured in a three level approach, where the first level consists of quite simple formulae. If a ship does not pass the first level, it is assumed that the ship is vulnerable to the phenomenon addressed, and the second level of criteria shall then be applied. This level consists of computations which are a little more complex, but they still treat the problems addressed in a strongly simplified manner. If now the ship does not pass the second level, a third level shall be applied to ensure that the ship can be designed and operated safely. This third level consists of direct calculation methods which shall be applied, however no criteria or procedures have yet been developed for this third level. We have applied the level 1 and level 2 criteria to a reference ship where a direct stability assessment has been performed during the design. The results showed extremely large scatter in the required GM-values of the criteria, and none of the criteria showed GM values roughly comparable to the direct assessment. The paper shows why the application of the criteria is challenging for the design of RoRo-ships and why a third level (direct assessment) is urgently required before the first two levels are put into force. Some conclusions are also drawn for the possible treatment of the new criteria in a stability booklet.

scholarly journals Little Big El-Mo

2001 ◽  
Vol 123 (10) ◽  
pp. 52-55 ◽  
Author(s):  
Paul Sharke
Keyword(s):  
High Temperature ◽  
Assembly Line ◽  
Naval Research ◽  
New Techniques ◽  
Ship Propulsion ◽  
High Temperature Superconducting ◽  
Superconducting Motor ◽  
Office Of Naval Research ◽  
The Us ◽  
The Many

This article reviews the arrival of commercial high-temperature superconducting (HTS) motors in the market. American Superconductor is concentrating its motor efforts on ship propulsion. The company has a contract with the US Navy’s Office of Naval Research to design and develop propulsion motors up to 33,500 hp. The big advantage of a superconducting motor aboard a ship is its small size, which frees up valuable square footage in the hull for the many other components needed in battle. Because superconducting motors will be about half the weight of their conventional counterparts, the efficiencies an assembly line brings to manufacturing suddenly open for many of them. Lighter, smaller designs also will translate to time saved in testing. Many of the technologies used in the 200-hp machine transferred to the 1000-hp unit, and many new techniques developed as well.

Risk-based Simulation Models for the Construction of the Mobile Offshore Base

2000 ◽  
Vol 16 (04) ◽  
pp. 241-252
Author(s):  
William J. Bender ◽  
Andrew N. Blair ◽  
Bilal M. Ayyub
Keyword(s):  
Simulation Models ◽  
Construction Cost ◽  
Simulation Software ◽  
Naval Research ◽  
Floating Structure ◽  
Feasibility Assessment ◽  
Office Of Naval Research ◽  
The Us ◽  
Resource Requirements ◽  
Mobile Offshore Base

Several very large ocean structures have been proposed as part of the Office of Naval Research feasibility study of a Mobile Offshore Base (MOB). The MOB platform nominally is about 1500 m (l mile) by 129 m (400 ft), which is unprecedented in size and operations compared to any floating structure to date. The objective of this study was to provide a risk-informed construction feasibility assessment for five proposed MOB concepts and quantify their construction cost and schedule. The risks associated with the concepts' cost and schedule were established by comparing resource requirements to build a MOB with the US industrial capacity. These risks were then modeled and simulated using commercial simulation software to provide cost and schedule estimates that accounted for uncertainty and risks. The scope of this study was limited to the construction of the hull.

Second Generation Intact Stability Criteria Fallout on Naval Ships Limiting KG Curves

2020 ◽  
Author(s):  
Gennaro Rosano ◽  
Ermina Begović ◽  
Guido Boccadamo ◽  
Barbara Rinauro
Keyword(s):  
Dynamic Stability ◽  
Second Generation ◽  
Loss Of Stability ◽  
Stability Criteria ◽  
Parametric Roll ◽  
Intact Stability ◽  
Surf Riding ◽  
Hull Forms ◽  
Onr Tumblehome ◽  
Dead Ship Condition

The International Maritime Organization (IMO) finalized the Second Generation Intact Stability Criteria (SGISC), in February 2020. They are intended to be included in Part A of the 2008 International Code on Intact Stability in the following years. The SGISC consider five modes of dynamic stability failure in waves: parametric roll, pure loss of stability, surf-riding/broaching to, dead ship condition and excessive acceleration. In this paper, two semi-displacement, round bilge and transom stern hull forms, the parent hull of the Systematic Series D and the ONR Tumblehome, i.e. typical naval hull forms, are examined. Although naval ships are not directly impacted by SGISC, they are sensitive to dynamic stability failure phenomena due to their geometry and range of service speeds. The procedures to assess the ship vulnerability to the dead ship condition and excessive acceleration criteria, referring to the latest drafts of the criteria (SDC 7/5, 2019), were implemented in Matlab®,. The limiting KG curves associated with this set of criteria were obtained for each vessel. The minimum allowable KG curve associated with the excessive acceleration criterion was compared with the maximum allowable KG curve associated with dead ship condition, to investigate the existence of a safe operational area.

Application of the Second Generation Intact Stability Criteria in Initial Ship Design

2014 ◽  
Author(s):  
M. Tompuri ◽  
P. Ruponen ◽  
M. Forss ◽  
D. Lindroth
Keyword(s):  
Second Generation ◽  
Failure Modes ◽  
Ship Design ◽  
Stability Criteria ◽  
Parametric Roll ◽  
Safety Measures ◽  
Main Emphasis ◽  
Intact Stability ◽  
Surf Riding ◽  
Additional Safety

The International Maritime Organization (IMO) is revising the Intact Stability Code. The so-called second generation intact stability criteria will provide additional safety measures against stability failures in waves. The draft regulations for three failure modes, parametric roll, pure loss of stability and surf-riding/broaching are reviewed and sample calculations for a fast RoPax ship are presented. The main emphasis is on the sensitivity of the results to the applied input data, which is not very accurate in the initial design phase. The implementation and effects of the new calculations to the ship design are discussed.

Sign in / Sign up

Export Citation Format

Share Document