Polski Rejestr Statków S.A., Gdańsk
Numerical solutions of nonlinear hydrodynamics problems with free surface
The paper presents numerical solutions of hydrodynamics problems with free surface developed in Polski Rejestr Statków during last several years. Modelling phenomenon of ship motion in waves, sloshing inside tanks or flooded holds and flow of trapped water on vessel deck requires special assumptions and algorithms. Accuracy of these methods significantly affects the solutions. The paper contains comparison of various methods. The studies contribute to better awareness of ship behaviour, capsizing phenomenon, failure of ship structure and other undesired events.
Volume of fluid technique, shallow water method, Boundary Element Method, Finite Elements Method, and others are used to solve the hydrodynamics problems. It is important to choose a model as simple as possible but without loosing sight of the essence of water behaviour. The proper determination of hydrodynamic forces acting on the moving ship in waves is very important in terms of safety.
Most hydrodynamics problems are solved with linear or quasi-linear assumptions. In determining the forces acting on the objects submerged in water the elevation of waves is neglected or the elevation is obtained from the linear part of Bernoulli equation.
Such phenomena as:
need more sophisticated methods, which describe the free surface elevation and consequently pressure exerted on the body with more accuracy.