scholarly journals Experimental study of the resistance to the movement of trimaran vessels

2021 ◽  
Vol 2131 (3) ◽  
pp. 032074
Author(s):  
A Korepanov ◽  
E Ronnov
Keyword(s):  
Froude Number ◽  
Research Design ◽  
Relative Position ◽  
Model Tests ◽  
Hydrodynamic Resistance ◽  
Design Stage ◽  
Mutual Position ◽  
Design Elements ◽  
Geometric Characteristics ◽  
Classical Principle

Abstract The aim of the work is to develop a method for finding the resistance of a trimaran ship at the initial stages of design, depending on the geometric characteristics of the central hull, outriggers and their mutual position. The program of model tests in the experimental tank is characterized. Based on the analysis of the experimentally obtained data, the graphs of the resistance dependence on the Froude number for the trimaran ship model with the fore, central and stern arrangement of outriggers are presented. A graph of the outriggers’ location influence along the vessel length on its hydrodynamic resistance is also shown. A method for calculating the hydrodynamic resistance for a trimaran vessel at the stages of research design is proposed, which is an adjustment of a single-hull vessel model tests’ recalculation classical principle. One of the developed graphs of the residual drag coefficient dependence on the relative speed according to the Froude number for various central hull geometric characteristics of the vessel, outriggers and their relative position is presented. The analysis of serial model tests made it possible to establish the dependence of the trimaran ship resistance on the geometric characteristics of the central hull and outriggers, and their relative position relative to each other in this study. The method proposed in this work will make it possible to substantiate the best layout of outriggers when solving the problem of optimizing the design elements and characteristics of a trimaran at the research design stage.

High-Speed Trimaran Drag: Numerical Analysis and Model Tests

2004 ◽  
Vol 48 (03) ◽  
pp. 248-259 ◽  
Author(s):  
Igor Mizine ◽  
Eduard Amromin ◽  
Leonard Crook ◽  
William Day ◽  
Richard Korpus
Keyword(s):  
Froude Number ◽  
Linear Theory ◽  
High Speed ◽  
Numerical Technique ◽  
Reynolds Numbers ◽  
Correlation Factor ◽  
Wave Resistance ◽  
Model Tests ◽  
Navier Stokes ◽  
Mutual Position

A numerical technique for high-speed trimaran resistance calculation is developed. The technique is based on the modified viscous-inviscid interaction concept and quasi-linear theory of wave resistance (Amromin et al 1984). The key element of this technique, which is called modified quasi-linear theory (MQLT), is an account of Froude number influence on the ship trim, transom drag, and wetted surface. This influence leads to appearance of a drag component that significantly depends on both Reynolds number and Froude number. This component has been traditionally included in residuary drag in the model test data. The presented preliminary numerical results were obtained with simplifications of the boundary layer theory that are acceptable for slender hulls. Calculated drag is in sufficient accordance with results of model tests. The MQLT computations of boundary layers are also compared with the Reynolds averaged Navier-Stokes (RANS) calculations(one-equation turbulence model by Spalart and Allmaras 1992) at model and ship scale Reynolds numbers. An analysis of the model-ship scale correlation factor for high-speed slender hulls with transom sterns and diverse mutual position of the trimaran hulls is done.

Model Tests for the Validation of Extreme Roll Motion Predictions

2002 ◽  
Author(s):  
Walter L. Kuehnlein ◽  
K.-E. Brink
Keyword(s):  
Practical Knowledge ◽  
Rapid Development ◽  
Model Tests ◽  
Design Stage ◽  
Roll Motion ◽  
Ministry Of Education ◽  
Following Seas ◽  
Early Design Stage ◽  
Shaped Container ◽  
Motion Characteristics

At present common stability criteria are based on practical knowledge gained from the operation of ships. Therewith the assessment of ship safety against capsizing is partly determined by long-term statistics of accidents. Regulations like the IMO-Resolution A 167 do not rate the typical seakeeping characteristics of different hull form geometries. Therefore strictly speaking, these criteria are just applicable for ships of similar types as included in statistics. Rapid development in ship design calls for the determination of ship and cargo safety in regard of extreme roll motions or capsizing during early design stage. Within the ROLL-S project, which was founded by the German Federal Ministry of Education and Research, dynamic stability tests with a box shaped Container Ship and a RO-RO vessel have been performed. The performance of model tests, which are intended to serve for the validation of numerical simulation methods, put high demands on test and data acquisition techniques. The data of the waves encountered, course and position, as well as the response of the model had to be determined by model tests in order to use these data for the validation of numerical ship motion simulations. During the tests extreme roll motions of the two considered vessels could be observed in head seas and in following seas. Besides critical motion characteristics in following seas, like broaching, parametric induced roll motion effects were investigated in head sea condition. Remark: This paper should be read in conjunction with paper OMAE 2002-28297 which describes generation and transformation of the used waves.

Evaluation of a Small and Fast Planing Boat’s Seakeeping Performance at the Design Stage

2015 ◽  
Author(s):  
Dong Jin Kim ◽  
Sun Young Kim
Keyword(s):  
Model Tests ◽  
Full Scale ◽  
Scale Model ◽  
Design Stage ◽  
Small Scale ◽  
Irregular Wave ◽  
Seakeeping Performance ◽  
Head Waves ◽  
Scale Ratio ◽  
Free Running

Seakeeping performance of a planing boat should be sufficiently considered and evaluated at the design stage for its safe running in rough seas. Model tests in seakeeping model basins are often performed to predict the performance of full-scale planing boats. But, there are many limitations of tank size and wave maker capacity, in particular, for fast small planing boats due to small scale ratio and high Froude numbers of their scale models. In this research, scale model tests are tried in various test conditions, and results are summarized and analyzed to predict a 3 ton-class fast small planing boats designed. In a long and narrow tank, towing tests for a bare hull model are performed with regular head waves and long crested irregular head waves. Motion RAOs are derived from irregular wave tests, and they are in good agreements with RAOs in regular waves. Next, model ships with one water-jet propulsion system are built, and free running model tests are performed in ocean basins. Wave conditions such as significant heights, modal periods, and directions are varied for the free running tests. Motion RMS values, and RAOs are obtained through statistical approaches. They are compared with the results in captive tests for the bare hull model, and are used to predict the full-scale boat performances.

scholarly journals 25 Years of Complex Intervention Trials

2017 ◽  
Vol 28 (5) ◽  
pp. 523-531 ◽  
Author(s):  
Kelli A. Komro
Keyword(s):  
Research Design ◽  
Complex Interventions ◽  
Well Being ◽  
Careful Consideration ◽  
Theory Of Change ◽  
Intervention Design ◽  
High Risk Behaviors ◽  
Design Elements ◽  
Group Randomized Trials ◽  
Intervention Trials

For the past 25 years, I have led multiple group-randomized trials, each focused on a specific underserved population of youth and each one evaluated health effects of complex interventions designed to prevent high-risk behaviors. I share my reflections on issues of intervention and research design, as well as how research results fostered my evolution toward addressing fundamental social determinants of health and well-being. Reflections related to intervention design emphasize the importance of careful consideration of theory of causes and theory of change, theoretical comprehensiveness versus fundamental determinants of population health, how high to reach, and health in all policies. Flowing from these intervention design issues are reflections on implications for research design, including the importance of matching the unit of intervention to the unit of assignment, the emerging field of public health law research, and consideration of design options and design elements beyond and in combination with random assignment.

Practical Structural Assessment of Offshore Structures for Wave Slap

2012 ◽  
Author(s):  
Joong Soo Moon ◽  
Tae Hyun Park ◽  
Woo Seung Sim ◽  
Hyun Soo Shin
Keyword(s):  
Static Pressure ◽  
Impact Load ◽  
Offshore Structures ◽  
Model Tests ◽  
Design Stage ◽  
Load Prediction ◽  
Structural Assessment ◽  
Pressure Impulse ◽  
The Impact ◽  
Design Pressure

By the combination of theoretical and empirical approach, the methodology for practical structural assessment of offshore structures for wave slap is proposed. It is developed for engineers in the sense that the precise design pressure is easily obtainable and quickly applicable in early and detail design stage. For impact load prediction, the Pressure-Impulse theory that was well developed and validated in coastal engineering field is applied. The impact pressures are classified into three types (traditional, sharp, and immersed slap) according to model tests and BP Schiehallion FPSO’s bow monitoring. The time histories of impact pressures for the classified impact types are generated with the pressure impulse predicted by the Pressure-Impulse theory. Nonlinear transient structural analyses are performed using the time series of impact pressures to obtain equivalent static pressure factors. Finally, the design pressure is determined by multiplying the maximum peak pressure by the equivalent static pressure factor. The results are validated through the comparison with model tests and dedicated reports.

scholarly journals Numerical Analysis of the Rudder–Propeller Interaction

2020 ◽  
Vol 8 (12) ◽  
pp. 990
Author(s):  
Diego Villa ◽  
Andrea Franceschi ◽  
Michele Viviani
Keyword(s):  
Flow Problem ◽  
Empirical Method ◽  
Design Stage ◽  
Mutual Position ◽  
Flow Solver ◽  
Additional Information ◽  
Computational Fluid Dynamics Cfd ◽  
Semi Empirical ◽  
Insight Into ◽  
Numerical Approaches

The proper evaluation of the Rudder–Propeller interactions is mandatory to correctly predict the manoeuvring capability of a modern ship, in particular considering the commonly adopted ship layout (rudder often works in the propeller slipstream). Modern Computational Fluid Dynamics (CFD) solvers can provide, not only the performance of the whole system but also an insight into the flow problem. In the present paper, an open-source viscous flow solver has been validated against available literature experimental measurements in different conditions. After an extensive analysis of the numerical influence of the mesh arrangement and the turbulent quantities on the rudder provided forces, the study focused its attention on the forces generated by the rudder varying the propeller loading conditions and the mutual position between the two devices. These analyses give a hint to describe and improve a commonly-used semi-empirical method based on the actuator disk theory. These analyses also demonstrate the ability of these numerical approaches to correctly predict the interaction behaviour in pre-stall conditions with quite reasonable computational requests (proper also for a design stage), giving additional information on the sectional forces distribution along the span-wise rudder direction, useful to further develop a new semi-empirical rudder model.

An Innovative Self Installing Platform (SIP) Concept

2011 ◽  
Author(s):  
Frank Slangen ◽  
Wim Bal ◽  
Mark Riemers
Keyword(s):  
North Sea ◽  
Water Depth ◽  
Structural Design ◽  
Pile Foundation ◽  
Design Stage ◽  
Process Equipment ◽  
Design Elements ◽  
The North ◽  
The North Sea ◽  
Outside Diameter

Centrica Energy (formerly Venture) selected a self installing and re-usable platform concept (SIP) to develop their F3FA gas field in the Northern Part of the Dutch sector of the North Sea. On 6 February 2009 and following an initial FEED study, the contract was awarded to Heerema Fabrication Group (Main Contractor and Fabricator), in partnership with Iv-Oil & Gas (Designer and Procurer of process equipment) and SPT Offshore (Installation Contractor and Foundation Designer). The platform weighed in total 8,800 ton, including a 4,000 ton deck and 4,800 ton substructure including the suction pile foundation. The water depth at the F3FA site is 41m and the bottom of the cellar deck is located at 20m above LAT. The platform has an overall dimension of 63m × 45m footprint and protrudes some 90m above the seabed (excluding vent stack). The platform concept consists basically of a deck of 5 levels supported by 4 unbraced legs (3.25m outside diameter × 77m long) and founded on 4 huge suction piles (15m outside diameter × 13m deep). The platform is transported and installed using a large flat top barge (BOA 35 measuring 124m long × 31.5m wide × 8m high) and 3 tug boats (75, 90 and 183 ton bollard pull) for the tow from HFG’s yard in Vlissingen to the F3FA site in the Dutch sector of the North Sea. The leg lowering and deck lifting was achieved using 12× 900 ton strand jacks. The suction pile foundation was installed using 4× suction pumps. During the detailed design stage of the project, the concept design was subject to several elementary changes in the structural design. This had to do with the severe environment, the increased deck weight and water depth compared to the earlier utilisation of the concept. Fatigue and transport and installation issues had a significant impact on several key structural design elements. This complicated the deck-leg connections and several members in the truss deck. The deck leg connection was amended from a simple clamp connection in to a superbolt and sleeve connection at the top deck and a clamped and grouted connection at the cellar deck. In order to improve the stiffness of the legs, leg stiffening frames were placed on top of the suction piles. Due to the limited and slow roll & pitch response of the platform whilst on the BOA barge during tow, high seafastening forces were predicted. These high seafastening forces were transferred in to the barge using pinned seafastening arms. Water depth limitations and the additional leg stiffening frames necessitated to use a fairly high grillage structure of 6.5m high. All these items changed the deck construction towards a method obstructing completion of non-structural disciplines and changed the inshore mating operation of the substructure with that topside towards a complex lifting and fitting campaign. Despite these elementary design changes and some rigorous changes in the planning of the various activities, the contract schedule was achieved in time. The above efforts had an obvious effect on the managerial issues towards the project. It required a doubling of the manning levels and engineering issues of in some cases R&D nature. Despite all these challenges and complications, the platform left Vlissingen well ahead of time, on 18 August 2010, to set sail for the F3FA site. Upon arrival in the field, the weather deteriorated severely and the tow was forced to seek shelter in Rotterdam. Just before arrival in Rotterdam severe waves were encountered up to 6–7m maximum. Upon inspection in Rotterdam, the design proved to be resilient as no signs of damage were observed. Following 10 days waiting on weather the platform was towed to the field for the second time. Installation and lifting the deck to the top elevation was achieved within a record time of 2 days and 4 hours. Thereafter the platform hook-up team continued to work on the platform including completing the deck leg connections, such as installation of superbolts at the top deck level and clamp shells, rubber pads and grout at the cellar deck level. Further hook-up work consisted of hooking up the life support systems before arrival of the drill rig on 14th October 2010. The drilling of the first well was completed early January 2011 and first gas was introduced in to the pipeline system since week 4 of 2011.

Theoretical Investigation on Ice Resistance Prediction Methods for Ships in Level Ice

2014 ◽  
Author(s):  
Daniela Myland ◽  
Sören Ehlers
Keyword(s):  
Physical Nature ◽  
Model Tests ◽  
Design Stage ◽  
Prediction Methods ◽  
Sufficient Information ◽  
Early Design Stage ◽  
Level Ice ◽  
Resistance Prediction ◽  
Ship Performance ◽  
Ice Resistance

The assessment of the ship performance in ice covered waters has become more and more important in view of the increased interest in Arctic field logistics and transportation. The performance of ice-going or ice breaking ships is usually defined by their ability to proceed in uniform level ice, where good performance means low ice resistance, high propulsion efficiency and continuous ice breaking. In order to assess the ice breaking performance in an early design stage, model tests may be executed or several theoretical methods may be applied to predict the ice resistance may be applied. Due to the physical nature of model tests, all processes, i.e. forces contributing to ice resistance are considered. Thus, the execution of model tests is still the most reliable method to determine the ice resistance. But with regard to the high costs of model tests there is continued demand to gain knowledge on the reliability of theoretical prediction methods. The applicability of the method of choice depends on the underlying assumptions of the method itself and thus the method’s capability to predict and consider physical phenomena of interest. In this paper model tests are used to evaluate the influence of hull shape parameters and ice conditions on the breaking process, i.e. the ice resistance and the ship performance. Based on the knowledge gained a systematic comparison of existing, representative ice resistance prediction methods is carried out. The methods considered are state-of-the-art techniques which the original publications introduced with sufficient information to allow for their use in this comparison. It focuses on the suitability of the existing methods as engineering tools for the prediction of different components, as well as the total ice resistance itself. The incorporation of the ice resistance contributions in the different prediction methods is presented and differences are identified. On this basis an assessment of the assumptions and simplifications of these different numerical methods is outlined.

scholarly journals Numerical Estimation of Hull Hydrodynamic Derivatives in Ship Maneuvering Prediction

2021 ◽  
Vol 28 (2) ◽  
pp. 46-53
Author(s):  
Radosław Kołodziej ◽  
Paweł Hoffmann
Keyword(s):  
Model Tests ◽  
Circular Motion ◽  
Computational Method ◽  
Design Stage ◽  
Hydrodynamic Characteristics ◽  
Ship Maneuvering ◽  
Hydrodynamic Derivatives ◽  
Captive Model Tests ◽  
Ship Maneuverability ◽  
Free Running

Abstract Prediction of the maneuvering characteristics of a ship at the design stage can be done by means of model tests, computational simulations or a combination of both. The model tests can be realized as a direct simulation of the standard maneuvers with the free running model, which gives the most accurate results but is also the least affordable, as it requires a very large tank or natural lake, as well as the complex equipment of the model. Alternatively, a captive model test can be used to identify the hydrodynamic characteristics of the hull, which can be used to simulate the standard maneuvers with the use of dedicated software. Two types of captive model tests are distinguished: circular motion tests (CMT) and planar motion mechanism tests (PMM). The paper presents an attempt to develop a computational method for ship maneuverability prediction in which the hydrodynamic characteristics of the hull are identified by means of computational fluid dynamics (CFD). The CFD analyses presented here directly simulate the circular motion test. The resulting hull characteristics are verified against the available literature data, and the results of the simulations are verified against the results of free running model tests. Reasonable agreement shows the large potential of the proposed method.

scholarly journals Modeling of Discrete Contacts for the Thermodynamic Element System of a Modular Wood-Milling Cutter

2021 ◽  
pp. 162-172
Author(s):  
Natalia Kapustina ◽  
◽  
Vladimir Malygin ◽  
Vladimir Melekhov ◽  
Vladimir Slutskov ◽  
...  
Keyword(s):  
Finite Element ◽  
Contact Interaction ◽  
Cutting Tool ◽  
Design Stage ◽  
Contact Conditions ◽  
Ongoing Research ◽  
Design Elements ◽  
Standard Design ◽  
Wood Cutting ◽  
Thermodynamic Processes

Operational capability of a modular wood-cutting tool depends, besides many factors, on the design features of cutting element fastening unit. There are no clear and precise methods that explain major factors influencing tool durability for selecting the design of the modular wood-cutting tool, which would meet production requirements. Thermodynamics modeling under contact interaction of elements enables to choose a design for effective application and increases the tool efficient life. The research purpose is modeling of thermodynamic processes in the cutter element fastening unit in the wood-cutting tool body in order to optimize the design, technological parameters and operating modes of the tool. The research subject is the contact interaction conditions and heat transfer processes between the device elements. The cutting element fastening unit is designed and the model of interaction between the parts of the mechanism of the modular wood-milling tool is developed. Further tasks, namely, development of a model of thermodynamic processes in the cutting element fastening unit, discussion of the results and identifying the recommendations for choosing the design of the modular wood-cutting tool at the design stage were realized in a work that continues the ongoing research. The finite-element model of rough wavy surfaces contact interaction of design elements was developed on the basis of standard design of a shell-type plain woodmilling cutter. The analysis concluded that further analytical modeling of contact conditions with existing parameters is possible. The contacting surfaces approach and the radii of single contact areas were determined taking into account the data of design and calculation of wood cutting forces. These results will be used next in modeling of thermodynamic processes. Methodology and research methods comprise theoretical study and mathematical modeling, including finite-element analysis. The models developed are possible to be used in the creation of a complex durability model of the wood-cutting tool with regard to other factors. The main result of this research stage is obtaining the model of contact conditions and initial data for further modeling of thermodynamic processes in the knife fastening unit in the milling body to predict its thermal condition.

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