Development of an Efficient Method to Calculate Springing Induced Higher Order Loads
Prof. Dr.-Ing. Bettar Ould el Moctar
Malte Riesner M.Eng..
The aim of this project is to further develop a three-dimensional boundary element method based on Rankine sources to predict sectional loads acting on ship structures in waves taking into account springing-induced hydroelasticity effects. Wave induced forces, leading to resonant ship responses, are subdivided into Froude-Krylov, radiation and diffraction forces. For higher order springing it is important to consider nonlinear effects related to Froude-Krylov forces. These forces are computed in each time step based on the instantaneous wetted surface. With regard to springing, diffraction and radiation forces can be treated in a linear way. They are computed in the frequency domain and transferred into the time domain using convolution integrals. To account for hydroelasticity effects, the flow equations are coupled with the equations of motion (rigid and elastic). The elastic deformations are computed using a modal decomposition approach to efficiently solve a reduced set of natural modes. A Vlasov beam and three dimensional Finite-Element models will be used. Further, simplified methods for prediction of hydrodynamic damping will be developed and verified. The methods to be developed are extensively validated using results from model tests and field methods based on Reynolds-Averaged-Navier-Stokes-Equations.
- Riesner, M., van Graefe, A., Shigunov, V. and el Moctar, O., “Prediction of non-linear ship responses in waves considering forward speed effects”. Journal of Ship Technology Research, Volume 63, Issue 3, 2016