  The water impact of an inclined flat plate and at high horizontal velocity is
experimentally investigated with focus on the fluid-structure interaction
aspects. Several test conditions have been examined by varying the vertical to
horizontal velocity ratio, the pitch angle and the plate thickness.
Measurements are performed in terms of strains, loads and local pressure. The
study highlights the significant changes in the strains and, more in general,
in the structural behaviour when varying the plate stiffness and the test
conditions. For some of the test presented, permanent deformations are also
found. The strong fluid-structure interaction is analysed by comparing the
simultaneous measurements of strains and pressures, and it is shown that the
deformation of the plate leads to a reduction of the pressure peak and to a
corresponding pressure rise behind it. The variation in the shape of the spray
root caused by the structural deformation are discussed based on both pressure
measurements and underwater images. Despite the reduction of the pressure peak
intensity, it is shown that the structural deformation leads to an increase in
the total loading up to 50% for the test conditions examined in this study. It
is also observed that in presence of large structural deformations the
hydrodynamic loads do not obey the scaling that works in the case of the thick
plates, and some practical conclusions about the scaling of tests in presence
of a strong fluid-structure interaction are provided.
