The work achieved with the sail dynamometer boat “Fujin”, and the role of full scale tests as the bridge between model tests and CFD

2014 ◽  
Vol 90 ◽  
pp. 72-83 ◽  
Author(s):  
Yutaka Masuyama
Keyword(s):  
Model Tests ◽  
Full Scale ◽  
Full Scale Tests

Continuing Development of Metal-Loss Severity Criteria, Including Width Effects

2020 ◽  
Author(s):  
Brian N. Leis
Keyword(s):  
Failure Criteria ◽  
Full Scale ◽  
Metal Loss ◽  
Pipe Failure ◽  
New Approach ◽  
Planar Shape ◽  
Wide Range ◽  
Level 1 ◽  
Full Scale Tests

Abstract The emergence in the early 1970s of what about a decade later became the first release of ASME B31G began the development and evolution of criteria to assess the severity of metal-loss defects. Motivated by the desire to reduce the conservatism embedded in B31G, the late 1980s saw the release of Modified B31G, with that same report also introducing RSTRENG, which quantified “riverbottom” effects. The desire to avoid excessive conservatism in their application to higher-strength Grades gave rise to alternative criteria for such applications. PCORRC appeared in 1997, with early versions of DNV RP-F101 and British Gas’ LPC-1 criteria following shortly thereafter. It has since become evident for isolated smooth-bottomed features that in addition to feature length and depth, its width can be a factor, as can its planar shape, and through-thickness profile. This paper builds on insight gained from the prior work, presenting and validating a Level 1 failure criteria for isolated metal-loss features. The defect-free term for this Level 1 criterion relies on the Zhu-Leis criterion for defect-free pipe failure. That criterion is coupled to a recalibrated defect term analogous to PCORRC, whose extension to include the effects of width is considered. The resulting Level 1 criterion is validated in reference to full-scale tests of pipe with metal-loss, which include a mix of real corrosion and flat-bottomed machined features. These tests consider Grades from Gr B to X100, a wide range of diameters and thicknesses, and in many cases the effect of width. Finite element results are used to illustrate the role of width. Benchmarked against almost 80 full-scale tests it is shown that this new approach affects a reduction in conservatism. At the same time, it provides clear benefits in regard to reduced predictive scatter, as well as a reduction in required maintenance, and the scope of features that must be considered in field-digs.

A Case Study of Dynamic Instability in a Planing Hull

1987 ◽  
Vol 24 (02) ◽  
pp. 143-163
Author(s):  
Louis Codega ◽  
James Lewis
Keyword(s):  
High Speed ◽  
Dynamic Instability ◽  
Test Procedure ◽  
Large Angle ◽  
Model Tests ◽  
Full Scale ◽  
Planing Craft ◽  
Normal Operating ◽  
Full Scale Tests

Soon after introduction into service, a class of high-speed planing boats began to exhibit a dynamic instability that manifested itself in the craft trimming by the bow, rolling to a large angle of heel to port, and broaching violently to starboard, all within five seconds. This behavior, which occurred within the craft's normal operating envelope, could not be attributed to operator causes and resulted in unacceptable operating restrictions being placed on the craft. After a number of unsuccessful attempts to remedy the problem, an investigation to research possible causes was undertaken. Concurrently, a test boat was instrumented to quantify its behavior and, most importantly, to record the hydrodynamic bottom pressures acting while this phenomenon occurs. The craft is described and initial attempts at solving the problem are outlined. The results of research on this type of phenomena in both planing craft and flying boats are presented. The instrumentation system, complex for this size craft, is detailed and the test procedure described. The results of the full-scale tests are given, along with qualitative comparisons with other craft that display a similar problem and model tests that would indicate the possibility of such instabilities. The cause of the instability is described and recommendations are made to avoid similar problems in future craft.

The Role of Rubber Hysteresis in Skidding Resistance Measurements

1960 ◽  
Vol 33 (1) ◽  
pp. 151-157 ◽  
Author(s):  
C. G. Giles ◽  
Barbara E. Sabet
Keyword(s):  
Full Scale ◽  
Hysteresis Loss ◽  
Test Results ◽  
Friction Coefficients ◽  
Hysteresis Losses ◽  
Testing Techniques ◽  
Full Scale Tests ◽  
Tread Rubber ◽  
Natural And Synthetic

Abstract In this paper the authors have tried to give examples of some of the more important ways in which Dr. Tabor's paper on the importance of rubber hysteresis has contributed to a better understanding of the mechanism of friction between tire and road. It is evident that a number of the problems presented by past test results may now be explained in terms of rubber hysteresis losses, in particular, the mechanism of the dependence of skidding resistance on temperature, and the differences in performance between natural and synthetic tires. In relation to testing techniques it draws attention to the importance of temperature and to the need to standardize the hysteresis loss properties of test tires in addition to the hardness of tread-rubber. Finally, the most important of all, as Dr. Tabor suggests, his work opens up the possibility of improvements in tire characteristics, which could result in greatly increased friction coefficients and hence greater freedom from skidding under wet conditions. The limited full-scale tests the authors have been able to make seem fully to confirm this possibility.

CFD Simulations of Lifeboat During Sailing Phase in Harsh Weather

2015 ◽  
Author(s):  
Vidar Tregde ◽  
Sverre Steen
Keyword(s):  
Degrees Of Freedom ◽  
Free Fall ◽  
Model Tests ◽  
Full Scale ◽  
Cfd Simulations ◽  
Thrust Coefficient ◽  
Cfd Models ◽  
Calm Water ◽  
Set Up ◽  
Full Scale Tests

A free fall lifeboat is going through several phases during a drop; sliding on the skid, rotation on skid, free fall, water entry, ventilation, maximum submergence, resurfacing and the sailing phase. In the sailing phase, the engine is running, providing propeller thrust, and the vessel is exposed to wind and waves while trying to run away from the host. CFD simulations of the lifeboat in the sailing phase have been run in regular Stokes 5th order waves, as well as simulations in irregular seas. The regular waves have been set up with different wave heights and wave periods. The set-up of waves have been done to fulfil the requirements in DNV-OS-E406, which is the DNV-GL offshore standard for design of free fall lifeboats. Validation of the CFD models are done with comparison to model tests from calm water tests as well as self-propelled model tests in waves. Results from full scale tests in calm water and in waves are also used in validation of CFD results. The hydrodynamic problem solved for 3 degrees-of-freedom (DOF) free running model in waves with thrust force from propeller is solved using the CFD software Star CCM+. A method for estimating thrust coefficient with a combination of full scale calm water results and results from CFD simulations is presented. The CFD simulations have shown to give acceptable accuracy for lifeboat in a seaway. Further, the CFD simulations have shown to be very useful for demonstrating fulfilment of requirements in the offshore standard for lifeboats in the sailing phase.

Correlation Allowances in Model Tests Results: A Delicate Balance Between Performance, Accuracy and Commercial Interests?

2016 ◽  
Author(s):  
Gerco Hagesteijn ◽  
Patrick Hooijmans ◽  
Karola van der Meij
Keyword(s):  
Model Test ◽  
Performance Prediction ◽  
Model Tests ◽  
Full Scale ◽  
Test Results ◽  
Power Performance ◽  
Low Light ◽  
Sea Trial ◽  
Performance Accuracy ◽  
Full Scale Tests

Model tests at ballast and design draught are used to convert the sea trial results from the ballast trial draught to the contractual design draught. Correlation allowances in model test results and their effect on the trial performance prediction are of major importance. Nowadays it is not only typical to verify the contract speed but also the EEDI certification requires a verification of the speed power performance of the vessel. The use of a to favorable CA-value may lead to attractive performance figures, but also leads to higher fuel consumption figures than expected. Furthermore the design point of the propeller is affected, which leads to a too low light running margin and in some cases to erosive cavitation. During a study, large spreading in the values of the correlation allowances for design draughts have been found for merchant vessels tested at different model test institutes, but at ballast trial draught the spreading is much less. Can it happen that some institutes select favorable correlations allowances on the basis of inaccurate trial data of shipyards? Or should we accept a large spreading in correlation allowances and have these indeed been confirmed by sea trials at design draught? This paper will present a discussion using the experience of a large full scale trial database as well as the accuracy of model and full scale tests.

Documentation of Operational Limits of Free-Fall Lifeboats by Combining Model Tests, Full-Scale Tests, and Computer Simulation

2009 ◽  
Author(s):  
Wojciech E. Kauczynski ◽  
Per Werenskiold ◽  
Frode Narten
Keyword(s):  
Wave Height ◽  
Model Test ◽  
Free Fall ◽  
Model Tests ◽  
Full Scale ◽  
Test Results ◽  
Extrapolation Methods ◽  
Basic Performance ◽  
Calm Water ◽  
Full Scale Tests

Historically, approval of lifeboats is based on a “calm water” philosophy through the SOLAS regulatory regime. In spring 2005 during offshore installation tests in calm water, unacceptable structural deflection of the roof for one type of free-fall lifeboat was revealed. Immediate actions were initiated by the Norwegian Oil Industry Association (OLF) and Statoil, including the goal of studying and documenting the main performance factors for free-fall lifeboats at up to a 100-year weather condition. In addition, OLF has request to develop relevant criteria for in depth classification of performance, and finally to upgrade urgently, when relevant, all free-fall lifeboats operating on the Norwegian continental shelf to the agreed standards. The basic performance criteria of free-fall lifeboat systems in emergency conditions are: structural strength, acceleration loads on passengers during water impact, boat forward speed immediately after water entry, and the manoeuvring away to a safe distance from the installation. Within the OLF-project, MARINTEK has performed an extensive model test program (over 25000 tests) with the 14 different types of free-fall lifeboats (launched by vertical drop or from a skid). Boat performances have been examined in different weather conditions, ranging from still water up to 11m wave height (regular waves and wind) or 7m (irregular significant wave height with corresponding wind). Calm water model test results have been compared to full-scale test results. In order to extend prognosis of the lifeboat performances up to 100-year storm condition (Hs = 15.7m), special extrapolation methods have been developed for studying the three basic performance areas, augmented by computer simulations applied for higher sea states. This paper presents example results and experiences gained from the model tests, full-scale tests and combined use of simulations and model test results. Experimental model test set-up and applied analysis and extrapolation methods are reviewed. Finally, the application of newly proposed performance and technical criteria is discussed.

scholarly journals FULL-SCALE INVESTIGATION OF BERTHING IMPACTS AND EVALUATION OF A HYDRAULIC-PNEUMATIC FLOATING FENDER

1966 ◽  
Vol 1 (10) ◽  
pp. 64
Author(s):  
Theodore T. Lee
Keyword(s):  
Energy Absorption ◽  
High Energy ◽  
Model Tests ◽  
Full Scale ◽  
Ship Motion ◽  
Hydrodynamic Effect ◽  
Research Station ◽  
High Energy Absorption ◽  
Full Scale Tests ◽  
Absorption Characteristics

Two experimental hydraulic-pneumatic floating fenders (camels) were in-service tested in protected and exposed harbors. Due to their high energy-absorption characteristics, the fenders were effective in reducing damage to piers, pier-fender systems, and berthing or moored ships. Their performance relative to a number of individual ship-impacts is discussed, conclusion^drawn, and recommendations made. Measurements as a function of time of ship velocity, berthing force, position of point of impact, and energy absorption by fenders are presented and discussed for 35 berthings involving 14 ships of from 1,400 to 17,600 tons displacement. Load-deflection and energy-absorption curves of the hydraulic and pneumatic fender bags are presented and discussed, and results compared with those predicted by theory. Berthing forces and energy-absorption characteristics are analyzed statistically; their relationships with point of impact are compared with those established with a model of a tanker by the Hydraulic Research Station, Wallingford, England. The resistance to ship motion including hydrodynamic effect is analyzed. It is concluded that hydrodynamic effect is an important parameter which requires further investigation. It is recommended that full-scale tests of berthing impact at exposed harbors be continued and that model tests of berthing impact be initiated, particularly tests of the resistance to ship motion, so that hydrodynamic mass can be properly evaluated.

Investigation of planing craft maneuverability using full-scale tests

2021 ◽  
pp. 147509022110303
Author(s):  
Kazem Sadati ◽  
Hamid Zeraatgar ◽  
Aliasghar Moghaddas
Keyword(s):  
Full Scale ◽  
Performance Characteristics ◽  
Forward Speed ◽  
Speed Reduction ◽  
Planing Craft ◽  
Full Scale Tests ◽  
Turning Maneuver

Maneuverability of planing craft is a complicated hydrodynamic subject that needs more studies to comprehend its characteristics. Planing craft drivers follow a common practice for maneuver of the craft that is fundamentally different from ship’s standards. In situ full-scale tests are normally necessary to understand the maneuverability characteristics of planing craft. In this paper, a study has been conducted to illustrate maneuverability characteristics of planing craft by full-scale tests. Accelerating and turning maneuver tests are conducted on two cases at different forward speeds and rudder angles. In each test, dynamic trim, trajectory, speed, roll of the craft are recorded. The tests are performed in planing mode, semi-planing mode, and transition between planing mode to semi-planing mode to study the effects of the craft forward speed and consequently running attitude on the maneuverability. Analysis of the data reveals that the Steady Turning Diameter (STD) of the planing craft may be as large as 40 L, while it rarely goes beyond 5 L for ships. Results also show that a turning maneuver starting at planing mode might end in semi-planing mode. This transition can remarkably improve the performance characteristics of the planing craft’s maneuverability. Therefore, an alternative practice is proposed instead of the classic turning maneuver. In this practice, the craft traveling in the planing mode is transitioned to the semi-planing mode by forward speed reduction first, and then the turning maneuver is executed.

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