Year: 2019 Language: english Author: Renske Maria Marijnissen Publisher: tu delft Edition: 1st ISBN: 000000000000 Format: PDF Quality: eBook Pages count: 105 Description: this is een thesis In the past decade several high performance tugs were involved in serious accidents. This encouraged the discussion about the current regulation for tugs, which are nowadays equipped with large power installations. Those regulations, set by class societies, distinguish thee types of stability, namely: tow-tripping, self-tripping and escort stability. The latter is analysed in this research. Class societies Bureau Veritas and ABS have set the following requirement to simulations tools used to predict the safety of escort tugs: "The numerical simulation tool should be able to analyse the dynamic effects before a steady state is reached." To fulfil this requirement, the existing performance prediction tool TugSim is extended to a four degrees of freedom time domain simulation tool. This tool is able to simulate the dynamic behaviour of tugs in escort operations. The challenge is to find accurate expressions for the hydrodynamic forces in this simulation tool, especially for the roll motion. To obtain these forces, a combination of several methods is used. So are the steady state force contributions, being the damping terms as a result of a pure sway velocity, obtained with TugSim. The pure roll damping is obtained using the results of some free decay tests together with the method of Ikeda, which accounts for the additional lift induced roll damping when sailing with forward speed. The remaining terms, coherent with the yaw velocity, are obtained using a combination of the semi-empirical method developed by V. Ankudinov and some turning cycle tests.
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Stability assessment of tugs in escort operations
Language: english
Author: Renske Maria Marijnissen
Publisher: tu delft
Edition: 1st
ISBN: 000000000000
Format: PDF
Quality: eBook
Pages count: 105
Description: this is een thesis
In the past decade several high performance tugs were involved in serious accidents. This encouraged the discussion about the current regulation for tugs, which are nowadays equipped with large power installations. Those
regulations, set by class societies, distinguish thee types of stability, namely: tow-tripping, self-tripping and escort
stability. The latter is analysed in this research.
Class societies Bureau Veritas and ABS have set the following requirement to simulations tools used to predict
the safety of escort tugs:
"The numerical simulation tool should be able to analyse the dynamic effects before a steady state is reached."
To fulfil this requirement, the existing performance prediction tool TugSim is extended to a four degrees of freedom
time domain simulation tool. This tool is able to simulate the dynamic behaviour of tugs in escort operations.
The challenge is to find accurate expressions for the hydrodynamic forces in this simulation tool, especially for
the roll motion. To obtain these forces, a combination of several methods is used. So are the steady state force
contributions, being the damping terms as a result of a pure sway velocity, obtained with TugSim. The pure roll
damping is obtained using the results of some free decay tests together with the method of Ikeda, which accounts
for the additional lift induced roll damping when sailing with forward speed. The remaining terms, coherent with
the yaw velocity, are obtained using a combination of the semi-empirical method developed by V. Ankudinov and
some turning cycle tests.
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