Ship Sinkage and Trim Predictions Based on a CAD Interfaced Fully Nonlinear Potential Model
- Andrea Mola (SISSA - International School for Advanced Studies) | Luca Heltai (SISSA - International School for Advanced Studies) | Antonio De Simone (SISSA - International School for Advanced Studies)
- Document ID
- International Society of Offshore and Polar Engineers
- The 26th International Ocean and Polar Engineering Conference, 26 June-2 July, Rhodes, Greece
- Publication Date
- Document Type
- Conference Paper
- 2016. International Society of Offshore and Polar Engineers
- Fluid Structure Interaction, Numerical Towing Tank, Boundary Element Method, Fully nonlinear potential
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We present the results of a model for ship ?uid-structure interaction simulations based upon the potential ?ow theory. The govering Laplace equation is complemented by non penetration boundary conditions on the boat surface and by fully nonlinear kinematic and dynamic water free surface conditions, written in semi-Lagrangian form. The hull is represented as a three dimensional rigid body subjected to the action of gravity and hydrodynamic forces.
The spatial discretization of the ?uid dynamic problem is carried out by means of an iso-parametric collocation Boundary Element Method (BEM), which only requires the discretization of the domain boundary surfaces. In such framework, the markers at which the free surface kinematic and dynamic boundary conditions are collocated correspond to the nodes of the computational grid. The application of such spatial discretization results in a system of Di?erential Algebraic Equations (DAE), which is time-integrated by means of an implicit Backward Di?erentiation Formula (BDF) scheme. As for the hull rigid body equations, they are added to the DAE system, so as to obtain a strong coupling between the ?uid dynamic and structural solvers.
Exploiting the simplicity of the surface grids required by BEM, the solver is fully integrated with CAD data structures. At the start of each simulation, the CAD ?le describing the hull is imported and used to automatically generate the computational grid. At each time step, the CAD surface is displaced in the current position, to obtain the proper horizontal positioning of the water nodes in contact with the hull.
The model has been implemented in a stand alone C++ software (WaveBEM). The results of the simulations are compared with sinkage, trim experimental data available for the DTMB-5415 hull.
In the last years, predictive ?ow simulations have become an increasingly common tool in ship and yacht design. The growing computational resources available and the consequent desire to explore new design con?gurations, is pushing researchers to develop models of higher complexity. In particular, design engineers demand accurate prediction of unsteady and nonlinear hydrodynamic loads on the hull, and reliable computations of nonlinear wave-induced ship motions.
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