A shipmooring program
The Sim.B.A.D. (SIMulation de Bateaux Amarrés sur Défenses) program allows the calculation of the mooring forces for a given type of vessel. PDSTRIP (Public Domain Strip Method) program, developed by H. Söding and V. Bertram provides the hydrodynamic parameters necessary to solve the linear hydrodynamic model in time domain (Cummins equation). It was simply adapted to obtain the characteristics of the desired parameters. This chain of programs is not intended to replace models that are more elaborate (3D models for example) but because of its quite fast operation, can provide useful information at the time of a pre-feasibility or feasibility study. The comparison with a certain number of results published in the literature (physical or mathematical models) shows that it can provide good orders of magnitude.
PDSTRIP:
PDSTRIP computes from the ship’s characteristics (cross-sectional strips of the wetted hull, displacement, position of centre of gravity, radii of gyration…) the following responses:
- Hydrostatic values,
- Added masses,
- Radiation damping values,
- First order wave forces,
- Drift forces.
Pre-processing:
The hydrodynamic data pre-processing enables to provide:
- The “infinity” added masses,
- The impulse response functions (“IRF”) of radiation damping values,
- The impulse response functions (“IRF”) of wave excitation and drift forces,
- Random wave time series according to different options: o With random phase, on the basis of Hs, Tp and different spectrum density models (Jonswap, Bretschneider, Torsethaugen, McCormick, OchiHubble, Wallop) , o With the Fast method, on the basis of Hs, Tp and different spectrum density models (Jonswap, Bretschneider, Torsethaugen, McCormick, OchiHubble, Wallop) , o With random phase, on the basis of Hs, Tp and a specific density spectrum, o Other options for wave time series: input as a specific file, regular waves.
- Time series of wave excitation forces,
- Time series of drift forces (3 options: no drift forces, mean forces, “Molin” variant).
SIMBAD program:
The SIMBAD program can be used to simulate the behavior of a moored ship, using the Cummins equation (time simulation) and taking into account the following elements:
- Random wave forces (excitation and drift, see above),
- Gusty wind forces (generation of wind speeds according to a wind spectrum),
- Forces induced by a passing ship,
- Linear or non-linear mooring characteristics for mooring lines and fenders, as well as rigid connection type mooring system.
Post-processing:
The results data post-processing enables to provide plots of time series and analysis of results (min, max, 1/3, 1/10 values) for:
- Mooring line and fender loads,
- Motions, speeds and accelerations at the center of gravity and at other possible points of the ship.
A specific program enables the calculation of the motions of a given type of vessel in response to the wave forces acting on the ship, calculated with the PDSTRIP program. A comparison with published data is also provided.
Some spreadsheets provide wind and current coefficients for different types of ships, such as published in the literature. A specific spreadsheet is dedicated to the Fujiwara method for the estimation of wind load coefficients.
A specific spreadsheet is dedicated to the estimation of passing ship induced forces on moored ships for an open jetty and vertical quay.
A program allows the estimation of forces induced by wind-assisted propulsion systems, namely a rigid wing sail or Flettner rotor.
A specific spreadsheet is dedicated to the estimation of water depth in a channel or canal, according to the ship and bottom related factors (wave response allowance to be determined externally).
A specific spreadsheet provides geometric (lengths, breadth, draft…) and hydrostatic characteristics (metacentric height, KG) for different types of ships.