| Author | Armaoğlu, E. |
| Title | Dynamic instability of semi-displacement monohulls |
| Conference/Journal | PhD-thesis Universities of Glasgow and Strathclyde |
| Month | June |
| Year | 2007 |
Abstract
The motions of a ship in semi-displacement region is investigated. The focus is on the vertical dynamic forces which should not be neglected at this speed range. Two approaches are used to identify these dynamic forces. First is an amalgamated approach that uses a database of dynamic forces acting on the ship depending on the running attitude and speed of the ship. This database can be obtained from either CFD calculations or experiments. The second approach is an engineering assumption which states that the dynamic forces are quasi-steady and independant of wave frequency for this speed region. This assumption is validated for semi-displacement region by seakeeping experiments for regular waves in 3 degrees of freedom. A manoeuvring mathematical model using horizontal body axis, which allows for a combination of seakeeping and manoeuvring models and takes into account high-amplitude motions, is used and the forces and motions are evaluated in six degrees of freedom in time domain. Various numerical methods are comparatively investigated and the current numerical model is tested for qualitative and quantitative agreement with experimental results. The effect of speed on manoeuvring hydrodynamic coefficients, control parameters and end effects are discussed. This new mathematical model is used to investigate unstable motions and create capsize boundaries for a semi-displacement craft.
The motions of a ship in semi-displacement region is investigated. The focus is on the vertical dynamic forces which should not be neglected at this speed range. Two approaches are used to identify these dynamic forces. First is an amalgamated approach that uses a database of dynamic forces acting on the ship depending on the running attitude and speed of the ship. This database can be obtained from either CFD calculations or experiments. The second approach is an engineering assumption which states that the dynamic forces are quasi-steady and independant of wave frequency for this speed region. This assumption is validated for semi-displacement region by seakeeping experiments for regular waves in 3 degrees of freedom. A manoeuvring mathematical model using horizontal body axis, which allows for a combination of seakeeping and manoeuvring models and takes into account high-amplitude motions, is used and the forces and motions are evaluated in six degrees of freedom in time domain. Various numerical methods are comparatively investigated and the current numerical model is tested for qualitative and quantitative agreement with experimental results. The effect of speed on manoeuvring hydrodynamic coefficients, control parameters and end effects are discussed. This new mathematical model is used to investigate unstable motions and create capsize boundaries for a semi-displacement craft.
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June 1, 2007