On the direct stability assessment of parametric rolling with CFD : Preparation for the Second Generation Intact Stability Criteria
Kosonen, Severi (2023)
2023
Teknis-luonnontieteellinen DI-ohjelma - Master's Programme in Science and Engineering
Tekniikan ja luonnontieteiden tiedekunta - Faculty of Engineering and Natural Sciences
This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Hyväksymispäivämäärä
2023-04-19
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:tuni-202303243171
https://urn.fi/URN:NBN:fi:tuni-202303243171
Tiivistelmä
Parametric rolling is a phenomenon where a ship starts to uncontrollably oscillate with increasing amplitude. This is caused by the surrounding waves parametrically amplifying the naturally occurring small rolling motions. The phenomenon can be dangerous, but the irregular nature of the sea makes it rare.
The International Maritime Organization is drafting a new type of assessment for ship stability in wave-related phenomena. This assessment is known as the Second Generation Intact Stability Criterion (SGISC), and parametric rolling is one of its focuses. The ship design is studied at three levels, where the computational complexity gradually increases. The final level is referred to as Direct Stability Assessment (DSA), where the phenomenon is modeled as accurately as possible. One possible method for this phase is Computational Fluid Dynamics (CFD) simulations, where the fluid flow surrounding the ship is numerically resolved from the Navier-Stokes equations. This allows the ship's response to waves to be accurately resolved without making any assumptions about the design.
This thesis studies the possibility of using CFD in the DSA phase for the parametric roll phenomenon. First, a literature survey was conducted on the hydrodynamics of the phenomenon, CFD, and the SGISC. Then, multiple CFD simulations were conducted. These simulations included the actual DSA simulation as well as supplementary simulations for other phases of the assessment. It was found that CFD is a valuable tool for studying the vulnerability to parametric rolling. However, the computational power required to directly study the parametric rolling may still be too high for a typical shipyard.
The International Maritime Organization is drafting a new type of assessment for ship stability in wave-related phenomena. This assessment is known as the Second Generation Intact Stability Criterion (SGISC), and parametric rolling is one of its focuses. The ship design is studied at three levels, where the computational complexity gradually increases. The final level is referred to as Direct Stability Assessment (DSA), where the phenomenon is modeled as accurately as possible. One possible method for this phase is Computational Fluid Dynamics (CFD) simulations, where the fluid flow surrounding the ship is numerically resolved from the Navier-Stokes equations. This allows the ship's response to waves to be accurately resolved without making any assumptions about the design.
This thesis studies the possibility of using CFD in the DSA phase for the parametric roll phenomenon. First, a literature survey was conducted on the hydrodynamics of the phenomenon, CFD, and the SGISC. Then, multiple CFD simulations were conducted. These simulations included the actual DSA simulation as well as supplementary simulations for other phases of the assessment. It was found that CFD is a valuable tool for studying the vulnerability to parametric rolling. However, the computational power required to directly study the parametric rolling may still be too high for a typical shipyard.