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Bowen Ma

Slug flow- and vortex-induced vibration of catenary risers.

Email: b.ma5@ncl.ac.uk

Project supervisors

Project description

Catenary risers connect subsea pipelines to deepwater oil production platforms. They transfer fluids between the platform and the pipeline. I am investigating slug-induced vibration (SIV) of flexible catenary risers subject to external excitations by vortex-induced vibration (VIV). I am focusing on the mechanical effects of slug gas-liquid flow characteristics. These include slug unit length, translational velocity and slug frequency. I am exploring their effects on the riser dynamics and the roles of SIV versus VIV in combined internal-external flow situations.

Methodology and objectives

I am adopting a mechanistic steady-state slug flow model. This distinguishes itself from other existing one-dimensional transient models, such as slug capturing and tracking. It allows a parametric investigation of the slug characteristics.

I will explore some of the important SIV aspects from the numerical study in laboratory tests. These include the individual and combined effects of slug length and velocity. I will compare the numerical prediction with experimental results for the limiting SIV cases to validate the model.

I will incorporate VIV effects. First, I will implement a phenomenological model based on wake oscillators. This will be for rigid structures under uniform flows. I will then examine the significance of planar SIV and VIV for the flexible catenary riser subject to slug flows and perpendicular uniform currents to the riser curvature.

Result

The results show fundamental and potential SIV effects on catenary risers. Slug unit length and slug translational velocity play significant roles. We should consider them individually when determining large-amplitude SIV. This is of practical importance from a design viewpoint. Thre are possible amplifications of riser responses due to slug flows in combined VIV-SIV scenarios. This is meaningful for the riser stress, fatigue and failure assessment. The current research paves the way for future development of computationally efficient tools. Such tools will provide benefits to the screening analysis of subsea risers transporting gas-liquid slug flows.

Publications

Qualifications

  • BEng (Hons) in Naval Architecture with Ocean Engineering from University of Strathclyde
  • Bachelor degree in Naval Architecture and Marine Engineering from Harbin Engineering University

 

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