Distortion model design of flexible marine riser

With the development of deep-sea oil and gas resources, the aspect ratio of deep-sea flexible riser has reached the order of 102–103, which makes the experimental model of the equal scale of deep-sea flexible risers challenging to achieve under typical experimental conditions. Alternatively, the non-scale experiment is sometimes used. However, the dynamic response of the prototype may not be exactly modeled. To solve the problem, this paper expands the distortion similarity method to consider the pretension and designs a distortion model of the deep-sea flexible riser based on the improved distortion similarity method. Applying the governing equation and dimensional analysis method to analyze the prototype and experimental model, the design method of the distortion model is obtained. In the numerical analysis, the design of the distortion model of a top tensioned riser (TTR) is carried out, and the selection criteria and range of the aspect ratio are proposed. The three parts of the natural frequency similarity, the pretension non-satisfaction similarity, and the error analysis are studied. This analytical study indicates that the transverse direction of the distortion model satisfies the similarity of the dynamics, and the longitudinal direction satisfies the static similarity. The selection of the aspect ratio of the distortion model should satisfy three factors.

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