Extrapolation of Propulsion Tests for Ships with Appendages and Complex Propulsors

2001 ◽  
Vol 38 (03) ◽  
pp. 145-157
Author(s):  
Jan Holtrop
Keyword(s):  
Scale Effect ◽  
Model Test ◽  
Test Results ◽  
Extrapolation Methods ◽  
Passive Components ◽  
Model Experiments

Prediction of ship powering is traditionally based on the results of model experiments. This paper covers the extrapolation of model test results for ships that may have a multitude of appendages and one or more complex propulsors. The major differences from conventional extrapolation methods are the application of the scale effect corrections to the model propulsion test, the treatment of the appendages and acknowledging the effects of the propeller load on the propulsion parameters. The last feature is considered essential to successfully handle complex propulsors with both rotating and passive components.

Algorithm and Experiment of the Separated Foundation Bearing Capacity of Culverts Considering Lateral Fill

2012 ◽  
Vol 450-451 ◽  
pp. 1616-1624
Author(s):  
Wen Lu Wang ◽  
Shu Jun Cui ◽  
Da Jun Zhao ◽  
Lei Wang
Keyword(s):  
Bearing Capacity ◽  
Model Test ◽  
Similarity Theory ◽  
Calculation Model ◽  
Test Results ◽  
Foundation Soil ◽  
Model Experiments ◽  
M 10 ◽  
Foundation Deformation ◽  
M 12

How to determine the foundation bearing capacity of high-stacked culverts in highway construction becomes a problem that must be taken seriously. Combining with the stress characteristics of the foundation soil, the soil force was analyzed for finding the improved effect on the separated foundation bearing capacity of lateral fill. Establishing the calculation model and algorithm, the general formulation of separated foundation bearing capacity considering lateral fill was deduced. Then under direction of similarity theory, six model experiments were designed to simulate the silt clay foundation deformation in whole loading process. The pressure-settlement curves were drew and the foundation bearing capacity under lateral fill height of 0 m, 4 m, 6 m, 8 m, 10 m, 12 m were measured. Test results showed that with the fill height increasing the bearing capacity increased significantly, it had been reached 815 kPa when the fill height was 10 m. But the growth was nonlinear, it first increased from 18.40% to 20.37% and then reduced to 8.59%. At last the bearing capacity reached 885 kPa while fill height exceeded 12 m. Meanwhile the errors between the calculated results and measured by model test were almost less than 10% so the algorithm was feasible. The conclusion is that the lateral fill is advantageous for improve the foundation bearing capacity and reduce project cost significantly when the settlement of the culverts foundation satisfied the design request, with the lateral fill increasing, the rate of the improvement first increases and then decreases, at last it tends to 885 KPa when fill height exceeded 12 m.

Warp Effects Studied by a Time-Domain Strip Model and Compared to Model Experiments

2020 ◽  
Author(s):  
Karl Garme
Keyword(s):  
Model Test ◽  
Time Domain ◽  
Method Development ◽  
Experimental Methods ◽  
Test Results ◽  
Regular Waves ◽  
Model Experiments ◽  
Strip Method ◽  
Calm Water ◽  
Research And Design

A time-domain strip method, in the Zarnick tradition, is used to discuss the modeling implications when alongships geometrical variations are studied, eg. warp or motion with frequent bow submergence. Results from simulations and published model test results for three warped hulls and their parent prismatic hull, in calm water and regular waves are presented. It is concluded that warp can be modelled by the strip approach. Non-the less, method development is proposed and the importance of combining different numerical end experimental methods both in research and design is stressed.

Study on Numerical Simulation of Jacket Launching Progress

2013 ◽  
Author(s):  
Lingzhi Xiong ◽  
Jianmin Yang ◽  
Xin Li ◽  
Xin Xu
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Scale Effect ◽  
Model Test ◽  
Hydrodynamic Force ◽  
Shallow Waters ◽  
Test Results ◽  
Physical Model Tests ◽  
Wave Basin ◽  
Similarity Law

Jacket type structures are widely used in shallow waters. The size of a jacket is determined by the dimensions of the deck and piles, as well as the environment loads. The jackets are usually transported with barges to the operation water after they have been fabricated in the shipyard, then the jackets slip into the water. Launch operation is the most hazardous stage during the installation of a jacket. The main purpose of this study is to evaluate the physical modeling test results for the launch, and compared to those of numerical simulation. It is found that there are some differences between the numerical simulations and physical model tests. The scale effect cannot be ignored in the prediction of the jacket launching process. The model test is based on the Froude similarity law, and the effect of Reynolds number is neglected. The drag coefficient depending on the Reynolds number plays a crucial role in determining the launch process. With different Reynolds number, the structure has different hydrodynamic force that results to different pitch angle, heave, launch time, acceleration and so on. Thus, a scale effect emerges when we convert the results of a wave basin model test to the prototype scale. This study also includes a sensitivity analysis about some key parameters in the launch process, such as initial barge trim and draft, frictions between barge and jacket.

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.

UJI TARIK HIDRODINAMIKMODEL KAPAL BERSAYAP WiSE DENGAN LAMBUNG DASAR BERSTEP

2013 ◽  
Vol 12 (3) ◽  
Author(s):  
Iskendar Iskendar ◽  
Andi Jamaludin ◽  
Paulus Indiyono
Keyword(s):  
Comparative Study ◽  
Model Test ◽  
Hydrodynamic Model ◽  
Surface Effect ◽  
Center Of Gravity ◽  
Test Results ◽  
Flat Bottom ◽  
Towing Tank ◽  
Test Models ◽  
Wetted Surface Area

This paper describes hydrodynamic model tests of Wing in Surface Effect (WiSE) Craft. These craft  was fitted with  stephull  form in different location on longitudinal flat bottom (stepedhull planning craft) to determine the influences of sticking and porpoising motion performances. These motions are usually occured when the craft start to take-off from water surfaces. The test models with scale of 1 : 7 were comprised of 4 (four) stephull models and 1 (one) non-stephull model  as a comparative study. The hydrodynamic  tests were performed with craft speed of 16 – 32 knots (prototype values) in Towing Tank at UPT. Balai Pengkajian dan Penelitian Hidrodinamika (BPPH), BPPT, Surabaya. The resistance (drag) was measured by dynamo meter and the trim of model (draft changing at fore and aft  of model due to model speed) was measured by trim meter. By knowing the value of model trim, the wetted surface area can be determined. Then, the lift forces were calculated based on these measured values. The model test results were presented on tables and curves.  Test results show that models  with step located far away from center of gravity of the WiSE craft tend to porpoising and sticking condition, except if the step location on the below of these center of gravity. While model without step tends to sticking conditions.

Inclined Loading Capacity of Embedded Suction Anchors in Clay

2009 ◽  
Author(s):  
Y. S. Kim ◽  
K. O. Kim ◽  
Y. Cho ◽  
S. Bang ◽  
K. D. Jones
Keyword(s):  
Analytical Solution ◽  
Model Test ◽  
Inclination Angle ◽  
Load Application ◽  
Centrifuge Model Test ◽  
Loading Capacity ◽  
Test Results ◽  
Pullout Capacity ◽  
Centrifuge Model ◽  
Inclined Loading

An analytical solution has been developed to estimate the inclined pullout capacity of an embedded suction anchor in clay seafloor. Validation has been made through comparisons with a limited number of centrifuge model test results. Results indicate that the inclined pullout capacity of an embedded suction anchor in clay decreases as the load inclination angle to the horizontal increases. As the point of the load application moves downward, the inclined pullout capacity increases, reaches its peak, and then starts to decrease.

Development and Verification of Modeling Practice for CFD Decay Calculations to Obtain Roll Damping of FPSO

2021 ◽  
Author(s):  
Arjen Koop ◽  
Pierre Crepier ◽  
Sebastien Loubeyre ◽  
Corentin Dobral ◽  
Kai Yu ◽  
...  
Keyword(s):  
Model Test ◽  
Test Results ◽  
Cfd Modelling ◽  
Roll Damping ◽  
Natural Period ◽  
Computational Mesh ◽  
Safety Studies ◽  
Offshore Industry ◽  
Decay Tests ◽  
Set Up

Abstract Estimates for roll damping are important input parameters for simulation studies on vessels operating at sea, e.g. FPSO mooring in waves, wind and current, workability and operability investigations, Dynamic Position studies, ship-to-ship operations and safety studies of vessels. To accurately predict the motions of vessels this quantity should be determined with confidence in the values. Traditionally, model experiments in water basins using so-called decay tests are carried out to determine the roll damping. With recent advancements in CFD modelling, the offshore industry has started using CFD as an alternative tool to compute the roll damping of FPSO’s. In order to help adopt CFD as a widely accepted tool, there is a need to develop confidence in CFD predictions. Therefore, a practical CFD modelling practice is developed within the Reproducible CFD JIP for roll decay CFD simulations. The Modelling Practice describes the geometry modelling, computational mesh, model set-up and post-processing for these type of CFD calculations. This modelling practice is verified and validated by three independent verifiers against available model test data. This paper provides an overview of the developed modelling practice and the calculated CFD results from the verifiers. The CFD modelling practice is benchmarked against available model test results for a tanker-shaped FPSO. By following this modelling practice, the CFD predictions for the equivalent linear damping coefficient and natural period of the roll motions are within 10% for all verifiers and within 10% from the model test results. Therefore, we conclude that when following the developed modelling practice for roll decay simulations, reliable, accurate and reproducible results can be obtained for the roll damping of tanker-shaped FPSOs.

FROUDE’S LAW OF SIMILITUDE – CONTEMPORARY AND FUTURE SEAKEEPING TESTING

2021 ◽  
Vol 153 (A2) ◽  
Author(s):  
R P Dallinga ◽  
R H M Huijsmans
Keyword(s):  
Model Test ◽  
Scale Effects ◽  
Higher Order ◽  
Air Pressure ◽  
Test Results ◽  
Viscous Effects ◽  
Two Phase ◽  
Scale Models ◽  
Non Linear

Historically “scale effects” in the interpretation of tests with scale models in waves using Froude’s Law of Similitude are mostly associated with viscous effects. Nowadays, with a much more complete modelling of reality and a focus on higher order non-linear phenomena, scaling of model test results implies a wider range of assumptions than the validity of Froude’s Law. Our contribution to the conference is a visionary review of contemporary and future problems in the interpretation of these tests. In this context we will discuss the developments in test techniques, including the development of a new Two-Phase Laboratory facilitating seakeeping and sloshing tests at reduced air pressure.

Outlier analysis of sloshing impact loads on liquid ship cargo

2022 ◽  
pp. 147509022110695
Author(s):  
Sang-Yeob Kim ◽  
Yonghwan Kim ◽  
Yang-Jun Ahn
Keyword(s):  
Model Test ◽  
Present Method ◽  
Treatment Method ◽  
Liquefied Natural Gas ◽  
Impact Loads ◽  
Test Results ◽  
Outlier Analysis ◽  
Load Prediction ◽  
Conventional Procedure

This paper introduces an outlier analysis which can improve the convergence of the statistical analysis results of sloshing model test data. The paper classify possible outliers in the sloshing model test into three categories and present a treatment method for each outlier. The developed outlier analysis is adapted to the model test results for the cargo of the liquefied-natural-gas (LNG) carrier in operation. The results of the present new method are compared with those of the conventional procedure, particularly focusing on long-term sloshing prediction. Through this study, the effectiveness of the present method is observed, and it is found that the present method provides is robust and reliable results in the application of experimental data for load prediction.

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