Experimental study of slamming pressure for a trimaran section with different drop heights and heel angles

Abstract

Trimarans may suffer from large motion and strong slamming accompanied by repeated water entry and water exit motions when sailing under severe sea conditions, and the huge instantaneous slamming load is prone to causing local structural damage. In this study, a free-drop water-entry model test of a trimaran section with different drop heights and heel angles was conducted. The motion and slamming pressure under different test conditions were compared, and the evolution of the free surface and flow field was observed using PIV (Particle Image Velocimetry) technology. We found that the peak value of the pressure was proportional to the square of the impact velocity, and that the peak pressure increased with the increasing heel angle on the lower side of the trimaran. Moreover, the flow separation phenomenon was more obvious at higher drop heights and larger heel angles. Finally, a Gaussian distribution function fitting model is proposed to fit the time-history curve of the slamming pressure within the slamming duration time on cross deck. The non-dimensional pressure coefficient and slamming action time under different conditions are summarised, and the fitting form which considers the impact velocity and impact angle in our results shows good agreement with the experimental data.