Natural frequency analysis of deep-sea mining riser considering varying tension and buffer station

The natural frequency of tensioned marine riser is important for deep sea mining pipe. The effects of varying tension along pipe and buffer station on natural frequencies and mode shapes are analyzed based on simplified beam model. The explicit expression of natural frequencies are given in terms of dimensionless weight of buffer and constant tension for cases of ω≫α and ω≪α through separation variable method. The results agree well with numerical results and regressions. Variation relations between natural frequency and dimensionless parameters of deep sea mining riser are given. Large variation tension along pipe are analyzed by power series method without buffer, the maximums of higher order mode shapes located nearer the upper end.