Effect of Boundary Conditions, Flow Rate, Slug Length, and Slug Frequency on Slug Flow Induced Vibration in a Pipeline Span

Abstract

Abstract This paper expands on the work described in OTC 22935 (Slug Flow Induced Vibration in a Pipeline Span, a Jumper, and a Riser Section [1]). Different boundary conditions of the pipeline span, flow rates, slug lengths, and slug frequencies are investigated for slug flow induced vibration of the pipeline span using the methodology proposed in OTC 22935. Coupled three-dimensional CFD of multiphase flow and transient nonlinear Computational Structural Dynamics (CSD) are implemented in fluid domain and structural domain. Recommended guidelines for reducing slug flow induced vibration in pipeline spans are generated from this investigation. Recommended guidelines for slug flow analysis using CFD alone or using coupled CFD with CSD are also presented. This paper has important and practical applications in designing pipeline spans and field operation of flow assurance to resist and reduce slug flow induced vibrations and fatigue damage due to slug flows in pipelines. The results illustrate the process of slug formation and decay inside the pipe, and the dynamic response of the pipe, including dynamic stresses and frequencies for different boundary conditions of the pipeline span, flow rates, slug lengths, and slug frequencies. The effect of above variables on slug flow induced vibration of the pipeline span has been quantified in detail. This paper quantifies slug formation and decay in a pipe while the pipe is also vibrating in response to this slug flow, accounting for the interaction between the two domains, for different boundary conditions of the pipeline span, flow rates, slug lengths, and slug frequencies. This paper provides a practical and very realistic tool for analyzing slug flow induced vibration and its induced fatigue damage and potential resonance response in pipeline spans. Important guidelines for better designs of pipeline spans and better management of flow assurance in field operation to resist and reduce slug flow induced vibration are proposed. Introduction Internal flow induced vibrations (FIV) have been observed in subsea jumpers during operation in subsea developments. Among the internal flows, slug flow is one of the most complicated phenomena in subsea pipelines, jumpers, and risers. A methodology for realistically modelling slug flow induced vibration in pipeline spans, jumpers, and risers was proposed in OTC 22935[1]. This methodology provides solutions to the slug flow induced vibration problems that DNV-OS-F201 (October 2010) [2] does not address. This paper expands on the work described in OTC 22935. The methodology proposed in OTC 22935 is used to investigate the effects of boundary conditions of a pipeline span, flow rates, slug lengths, and slug frequencies on slug flow induced vibration of the pipeline span. The numerical simulation examples are presented to illustrate the effects. A summary and conclusion is provided after the numerical examples.