Study on Natural Vibration Frequency and Mode Shape of Deep Sea Top Tensioned Riser

Abstract

In order to analyse the natural vibration frequencies and mode shapes of deep sea top tensioned riser, an analysis model is established in the present study. The effect of in-line bending displacement on riser natural vibration is considered in the present model. The finite element method is adopted in this paper to calculate the natural vibration frequencies and mode shapes of the riser. The effect of top-tension force and sea current velocity on the riser vibration frequencies and mode shapes has discussed in the present study. Results show that the riser vibration frequency of the in-line direction is higher than the cross-flow direction and the vibration mode shapes of the riser are not standard sinusoidal curve. The riser mode shapes of the in-line direction are different from the cross-flow direction. Moreover, the change of top-tension force and sea surface current velocity has a great influence on the riser vibration frequencies and mode shapes.