Investigation effect of circumferential mode number on natural frequencies of under-water vibrations of cylindrical shells numerically and experimentally

In the present study, the effect of circumferential mode number on natural frequencies of cylindrical shells was investigated numerically and experimentally. Three cylindrical shells with different diameter to length ratios were examined. Different contact type with water were compared using both numerical simulation and experimental tests. The effects of immersion depth, diameter to length ratio, variations of natural frequency with different circumferential mode number were investigated. The reduction of the natural frequencies of the cylindrical shell for the minimum frequency of different circumferential mode number is low, but it increases for higher and lower frequencies, and at the beginning of immersion and at full immersion, the frequency decreases suddenly. Also, as the ratio of diameter to shell length decreases, the frequencies of the low circumferential mode number decrease and the lower value of the natural frequency tends to lower circumferential mode number. At low circumferential mode number, the natural frequencies differ considerably, and with increase of n number, the difference decreases and converges.