Saeed Jaamei

Longitudinal instability (porposing) is one of the most important issues in headwinds due to its adverse effect on hydrodynamic performance. In recent years, the adverse effect of the porposing phenomenon on the performance of head vessels has been noted. In this paper, the effect of porpoising phenomenon on the hydrodynamic behavior of a stepped-headed floating vessel with fixed floor rise is investigated and then, with the increase of floor slope angle in this spring, the phenomenon of porpoiseing is re-examined and the hydrodynamic behavior is reversed. The resulting phenomenon of porposing has been done using numerical simulations. Based on the results of numerical simulation, the change in floor rise and its increase has eliminated the phenomenon of porpoising and also the increase in floor rise has increased the speed and efficiency of the drift system in the results. As a result, the onset of the porpoising phenomenon also increases with the rise of the critical dynamic curve. Therefore, according to the optimal hydrodynamic behavior of the new body, the vessel is built in 1: 1 scale and sea tests are performed on it. According to the results of these experiments, the phenomenon of porposing has been eliminated. By comparing the numerical results of numerical and sea experiments, the accuracy of the numerical simulation process of the new floating hydrodynamic behavior is observed.