scholarly journals Validation of Ship Manoeuvring in Shallow Water Through Free-Running Tests

2015 ◽  
Author(s):  
Katrien Eloot ◽  
Guillaume Delefortrie ◽  
Marc Vantorre ◽  
Frans Quadvlieg
Keyword(s):  
Mathematical Model ◽  
Numerical Methods ◽  
Mathematical Models ◽  
Shallow Water ◽  
Model Tests ◽  
Water Effect ◽  
Ship Manoeuvring ◽  
International Collaborations ◽  
Free Running ◽  
Shallow Water Effect

The shallow water effect on ship manoeuvring cannot be neglected. Most sea-going ships become more course stable when they sail from deep to (very) shallow water. International collaborations such as SIMMAN intend to grade up the knowledge on ship manoeuvring prediction through model tests and system based and numerical methods. Free-running model tests executed with the very large crude carrier KVLCC2 at two laboratories have been compared with the results of simulated turning circles and zigzag manoeuvres from two different mathematical models. It was concluded that the type of mathematical model has an important influence on the simulated behaviour. Moreover, further research is necessary as simulations result into a more course stable behaviour compared to free-running tests at model scale.

Experimental Investigation of Trimaran Models in Shallow Water

2014 ◽  
Vol 30 (02) ◽  
pp. 66-78
Author(s):  
Mark Pavkov ◽  
Morabito Morabitob
Keyword(s):  
Shallow Water ◽  
Water Depth ◽  
Critical Speed ◽  
Water Effect ◽  
Finite Water Depth ◽  
Speed Regime ◽  
Displacement Speed ◽  
Littoral Combat Ship ◽  
Shallow Water Effect ◽  
The U.S

Experiments were conducted at the U.S. Naval Academy's Hydromechanics Laboratory to determine the effect of finite water depth on the resistance, heave, and trim of two different trimaran models. The models were tested at the same length to water depth ratios over a range of Froude numbers in the displacement speed regime. The models were also towed in deep water for comparison. Additionally, the side hulls were adjusted to two different longitudinal positions to investigate possible differences resulting from position. Near critical speed, a large increase in resistance and sinkage was observed, consistent with observations of conventional displacement hulls. The data from the two models are scaled up to a notional 125-m length to illustrate the effects that would be observed for actual ships similar in size to the U.S. Navy's Independence Class Littoral Combat Ship. Faired plots are developed to allow for rapid estimation of shallow water effect on trimaran resistance and under keel clearance. An example is provided.

Paper 26. Stability and Control in Waves: A Survey of the Problem

1972 ◽  
Vol 14 (7) ◽  
pp. 186-193 ◽  
Author(s):  
J. E. Conolly
Keyword(s):  
Mathematical Models ◽  
Orbital Motion ◽  
Model Tests ◽  
Point Of View ◽  
Stability And Control ◽  
Free Running ◽  
And Control

Manoeuvrability in waves is discussed from the point of view of the dangers of broaching-to when a ship is running before the sea. Conditions are assessed under which this may occur, illustrated by documented cases, including the Wahine disaster in 1968. Because of the problems involved in investigating broaching-to by means of free-running model tests, there is an urgent need for reliable mathematical models: however, theories published so far, based on two different simplifications, are shown to have limitations. It is argued that the theory must take account of pitching, surging, rolling and orbital motion of the water particles.

scholarly journals Confirmation of shallow water effect in swimming pool

2004 ◽  
Vol 7 (1) ◽  
pp. 59-65
Author(s):  
Tokuzo FUKAMACHI ◽  
Tetsuo KAWASE ◽  
Yoshiaki TSUKADA
Keyword(s):  
Shallow Water ◽  
Swimming Pool ◽  
Water Effect ◽  
Shallow Water Effect

Estimation of Hydrodynamic Coefficients of a Nonlinear Manoeuvring Mathematical Model With Free-Running Ship Model Tests

2018 ◽  
Vol Vol 160 (A3) ◽  
Author(s):  
Haitong Xu ◽  
M A Hinostroza ◽  
C Guedes Soares
Keyword(s):  
Mathematical Model ◽  
System Identification ◽  
Model Tests ◽  
Loss Functions ◽  
Identification Algorithm ◽  
Hydrodynamic Coefficients ◽  
Global Optimization Algorithm ◽  
Identification Process ◽  
Ship Model ◽  
Free Running

Free-running model tests have been carried out based on a scaled chemical tanker ship model, having a guidance, control and navigation system developed and implemented in LabVIEW. In order to make the modelling more flexible and physically more realistic, a modified version of Abkowitz model was introduced. During the identification process, the model’s structure is fixed and its parameters have been obtained using system identification. A global optimization algorithm has been used to search the optimum values and minimize the loss functions. In order to reduce the effect of noise in the variables, different loss functions considering the empirical errors and generalization performance have been defined and implemented in the system identification program. The hydrodynamic coefficients have been identified based on the manoeuvring test data of free-running ship model. Validations of the system identification algorithm were also carried out and the comparisons with experiments demonstrated the effectiveness of the proposed system identification method.

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