Investigation effect of wetted surface of cylindrical shell on vibrational frequency in different immersion depth numerically and experimentally

In this paper, effect of wet surface of cylindrical shell on vibrational frequency in contact with water in different immersion depth is investigated vertically and numerically. Three steel cylindrical shells with different D/L ratio are investigated. Numerical simulation and experimental tests were compared in eight different type of water-shell contact. Effects of immersion depth, effect of difference of water-shell contact between the inner and outer surface with water and wet surface geometry for semi-immersed in vertical and horizontal direction are evaluated. The results show that the natural frequencies are suddenly reduced at the beginning of immersion and its end (full immersion). The reduction of natural frequencies in two modes of contact between the inner surface of the cylindrical shell and water as well as its outer surface contact with water is equal. For the equal wet area, more natural frequency reduction was observed at a horizontal position compared with the vertical position. Also, in the equal wetted surface, more frequency reduction is observed in horizontal than vertical directions.