DEFINING PARAMETERS OF EQUILIBRIUM STRANDING OF A SHIP USING SIMULATION MODELLING

Abstract

Equilibrium stranding of a ship is a necessary preliminary step for application of other decision support system algorithms, such as identification of a flooded compartment, predicting an emergency vessel capsize probability, and others. The equilibrium stranding using a real ship as an example based on the heel angle sensors readings for rolling and pitching, and the water column pressure sensors readings for the vertical roll, is calculated. In the linear case, the mean value of an individual value coincides with the equilibrium position on the corresponding coordinate axis. However, a ship rolling in a sea is, as a rule, non-linear process, and hence the mathematical average correction is required. The use of the Nechaev’s method for determining the equilibrium position of a floating vessel in a heavy sea is illustrated in the paper. An algorithm based on simulation modeling in the Virtual Testbed software package is proposed. It has been proved that complication of wave model used for coefficients obtaining in Y. I. Nechaev’s algorithm changes obtained equilibrium parameter value insignificantly, but in this case time spent for generation of one simulation is increased significantly enough. When using linear waves or Stokes waves, the generation of two minutes of simulation is faster than two minutes of real time; when using Gerstner waves, the simulation time approaching three minutes of real time, which already exceeds the simulation time. In this case, when using the Stokes waves model, it is possible to achieve the results closer to the Gerstner model than when using the linear waves model without consuming additional time. This fact allows us to conclude about the optimal use of the algorithm.