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.

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.

Experimental Study on Hydrodynamics of Hybrid Deep-V Monohull With Different Built-Up Appendages

2018 ◽  
Author(s):  
Shuzheng Sun ◽  
Hui Li ◽  
Muk Chen Ong
Keyword(s):  
Model Test ◽  
Performance Model ◽  
Hydrodynamic Performance ◽  
Irregular Waves ◽  
Hydrodynamic Characteristics ◽  
Vertical Acceleration ◽  
Test Results ◽  
Regular Waves ◽  
Sea State ◽  
Seakeeping Performance

The hydrodynamic characteristics of a hybrid deep-V monohull with different built-up appendages are investigated experimentally in order to improve the resistance and seakeeping performance. Model tests have been carried out to study the hydrodynamic performance between a bare deep-V vessel and a deep-V monohull with different built-up appendage configurations (i.e. a hybrid deep-V monohull). From the model test results, it is found that the existence of the appendages will reduce the amplitude of pitching angle and bow vertical acceleration compared to that of the bare deep-V vessel in heading regular waves. However, the resistances for the hybrid deep-V monohull with built-up appendages are increased 15.6% for Fn = 0.264, and 0.1% for Fn = 0.441 compared to the resistance of the bare deep-V vessel. The model test results of seakeeping performance in irregular waves show that the hybrid deep-V monohull gives a better seakeeping performance than the deep-V vessel. The pitching angle and bow vertical acceleration of the hybrid deep-V monohull containing a built-up appendage are reduced 15.3% and 20.6% compared to the deep-V monohull in irregular waves at Fn = 0.441 in 6th class sea state (H1/3 = 6m).

Experimental Investigation of Wave Loads Based on Trimaran Self-Propulsion Model

2016 ◽  
Author(s):  
Wei Xiaobo ◽  
Huilong Ren ◽  
Yanlong Sun ◽  
Di Wang ◽  
Zhen Yu Wang
Keyword(s):  
Model Test ◽  
High Speed ◽  
High Performance ◽  
Similarity Theory ◽  
Scale Model ◽  
Comprehensive Model ◽  
Wave Loads ◽  
Test Results ◽  
Regular Waves ◽  
Test Study

Trimaran, as a high performance ship, its special ship form is different from regular monohull ship. The particular characteristics of longitudinal and transverse wave loads are concerned greatly by ship structure designers. Theoretical methods for forecasting the wave loads of trimaran are under developing. And the relative comprehensive model test study of trimaran’s wave loads is rare in the publication. In this paper, the trimaran model test had been carried out in the tank. According to similarity theory and simulation of stiffness, a scale model of trimaran with measurement system had been manufactured. Then the segmented model had navigated in regular waves of different sea conditions. Through analysis of the experimental data, the wave loads characteristics of this trimaran are presented. A comparison of test results and theoretical values is also made to show the similarities and differences. This study can provide some useful information for further design of high-speed trimaran in the point of wave loads, which maybe a reference for research of trimaran.

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.

Time-domain numerical research of the hydrodynamic characteristics of a trimaran in calm water and regular waves

2019 ◽  
Vol 194 ◽  
pp. 106669
Author(s):  
Rui Deng ◽  
Fuqiang Luo ◽  
Tiecheng Wu ◽  
Siyuan Chen ◽  
Yulong Li
Keyword(s):  
Time Domain ◽  
Hydrodynamic Characteristics ◽  
Regular Waves ◽  
Calm Water ◽  
Numerical Research

CFD and EFD Based Studies of Hull Wetness of Fast Mono-WPC

2016 ◽  
Author(s):  
Chengzhu Wei ◽  
Yinghui Li ◽  
Hong Yi
Keyword(s):  
Numerical Methods ◽  
Numerical Simulations ◽  
Froude Number ◽  
Experimental Methods ◽  
Long Waves ◽  
Irregular Waves ◽  
Regular Waves ◽  
High Speeds ◽  
Calm Water ◽  
High Froude Number

Fast mono-wave-piercing craft (Fast Mono-WPC) use a tumblehome design and run at high speeds. Efforts have been made to study hull wetness problems because of the special hull shape and running state of Fast Mono-WPC. Numerical and experimental methods were adopted to study hull wetness problems of Fast Mono-WPC both in calm water and waves. Numerical methods were based on RANS. Dynamic mesh methods were used to simulate model motions. Influence of velocity, spray strips and hull motions on hull wetness of Fast Mono-WPC in calm water was studied. Results of CFD and EFD in calm water show that hull wetness of Fast Mono-WPC is sensitive to hull motions such as heave and pitch, and spray strips on the bow can reduce hull wetness. Model tests in regular and irregular waves and numerical simulations in regular waves of a free Fast Mono-WPC model were conducted at a high Froude number, Fn = 0.815. Numerical results show that wetness is slight when Fast Mono-WPC runs in 1L-long and 4L-long waves, and water climbs up the freeboard to the deck when Fast Mono-WPC cuts through 2L-long waves. Serious hull wetness was also experimentally observed both in regular and irregular waves.

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.

A Simple Method for Predicting the Maximum Squat of a High-Speed Displacement Ship

2006 ◽  
Vol 43 (03) ◽  
pp. 146-151
Author(s):  
Tim Gourlay
Keyword(s):  
Satisfactory Agreement ◽  
Model Test ◽  
High Speed ◽  
Simple Formula ◽  
Test Results ◽  
Simple Method ◽  
Wide Range ◽  
Speed Range ◽  
Calm Water ◽  
Hull Forms

A simple formula is developed for predicting the maximum squat of a displacement ship as it passes through the transcritical speed range. This is given in terms of a maximum sinkage coefficient, which is almost constant across a wide range of hull forms. Satisfactory agreement is shown with model test results, and it is shown that large stern sinkages in the order of 3 to 6 meters are predicted for frigate and destroyer type hulls in shallow calm water.

scholarly journals Test Studies of the Resistance and Seakeeping Performance of a Trimaran Planing Hull

2015 ◽  
Vol 22 (1) ◽  
pp. 22-27 ◽  
Author(s):  
Weijia Ma ◽  
D. Hanbing Sun ◽  
D. Huawei Sun ◽  
D. Jin Zou ◽  
Jiayuan Zhuang
Keyword(s):  
Small Angle ◽  
Test Results ◽  
Regular Waves ◽  
Longitudinal Stability ◽  
Towing Tank ◽  
Centre Of Gravity ◽  
Air Jets ◽  
Seakeeping Performance ◽  
Calm Water ◽  
The Stability

Abstract Towing tank tests in calm water were performed on a trimaran planing hull to verify its navigational properties with different displacements and centres of gravity, as well as to assess the effects of air jets and bilge keels on the hull’s planing capabilities, and to increase the longitudinal stability of the hull. Hydrostatic roll tests, zero speed tests, and sea trials in the presence of regular waves were conducted to investigate the hull’s seakeeping ability. The test results indicate that the influence of the location of the centre of gravity on the hull resistance is similar to that of a normal trimaran planing hull; namely, moving the centre of gravity backward will reduce the resistance but lower the stability. Bilge keels improve the longitudinal stability but slightly affect the resistance, and the presence of air jets in the hull’s channels decreases the trim angle and increases heaving but has little effect on the resistance. Frequent small-angle rolling occurs in waves. The heaving and pitching motions peak at the encounter frequency of , and the peaks increase with velocity and move towards greater encounter frequencies. When the encounter frequency exceeds, the hull motion decreases, which leads to changes in the navigation speed and frequency.

An Analysis of Chain Forces of a SBS Under Regular Wave Action

1983 ◽  
Vol 105 (3) ◽  
pp. 333-336
Author(s):  
Yu-Xiu Yu
Keyword(s):  
Model Test ◽  
Storage System ◽  
Oil Production ◽  
Wave Action ◽  
Test Results ◽  
Regular Wave ◽  
Static Characteristics ◽  
Regular Waves ◽  
Chain Force

Since the first Single Buoy Storage System (SBS) installed in Aquitaine-Tunisia in 1974 [1, 2], many similar systems have been installed. To facilitate oil production in Gulf Bohai, China, a model test of a SBS to investigate its motion and the forces under the action of regular waves has been carried out. Consulting the test results, this SBS “OFFSHORE 621” has been designed and launched. In this paper, the methods for determining the static characteristics of the multichain anchoring buoy system (MABS) and the measure for decreasing the chain force are given.

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