Temporal-spatial mode competition in slug-flow induced vibration of catenary flexible riser in both in plane and out of plane

To meet market demand for the high data density on the disk of a hard disk drive (HDD), reduction of disturbance causing track misregistration is needed. The main disturbance in HDDs in a server or a desktop PC is flow-induced vibrations caused by airflow due to the disk rotation. Generally, there are two kind of flow-induced vibration (FIV) of the structures inside a HDD. One is in-plane or out of plane vibration of the read/write component, i.e., the carriage. Another is out of plane vibration of the disk. In these experiments, we tried to reduce out of plane vibration of the disk and the carriage by making a simple structural change. The investigation is carried out to clear up a cause of FIV of the carriage. The result showed that the outflow from the disk region is strong and can be the cause of the out of plane vibration of both the disk and carriage. To counteract this fluid force, the plates were put against the disks to prevent wind disturbance. As a result, the flow-induced vibrations of the carriage and the disks were significantly reduced. Based on our results, we designed an anti-FIV structure.

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Slug Flow and Waves Induced Motions in Flexible Riser

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4037842 ◽

2017 ◽

Vol 140 (1) ◽

Cited By ~ 5

Author(s):

Arturo Ortega ◽

Ausberto Rivera ◽

Carl M. Larsen

Keyword(s):

Dynamic Analysis ◽

Slug Flow ◽

Distributed Simulation ◽

Coupled Analysis ◽

Induced Response ◽

Element Formulation ◽

Wave Loads ◽

Flexible Riser ◽

Two Phase ◽

Slender Structure

Flexible risers provide optimum solutions for deep water offshore fields. Reliable dynamic analysis of this kind of slender structure is crucial to ensure safety against long time fatigue failure. Beyond the effects from wave loads, the influence from transient internal slug flow on the slender structure dynamics should also be taken into account. In this study, two coupled in-house codes were used in order to identify and quantify the effects of an internal slug flow and wave loads on the flexible riser dynamics. One code carries out a global dynamic analysis of the slender structure displacements using a finite element formulation. The other program simulates the behavior of the internal slug flow using a finite volume method. The slug flow is influenced by the dynamic shape of the riser, while the time varying forces from internal slug flow plus external waves will influence the shape. Hence, a fully coupled analysis is needed in order to solve the coupled problem. By means of the distributed simulation, these two programs run synchronously and exchange information during the time integration process. A test case using hydrodynamic forces according to the linear Airy wave theory coupled with an internal unstable slug flow was analyzed and the results shown amplification of the dynamic response due to the interaction between the two load types, effects on the effective tension caused by the internal two-phase flow, and influence on the internal slug flow caused by the wave-induced response.

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Slug Flow Induced Vibration in a Pipeline Span, a Jumper and a Riser Section

10.4043/22935-ms ◽

2012 ◽

Cited By ~ 5

Author(s):

David Jia

Keyword(s):

Slug Flow ◽

Flow Induced Vibration

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B31 J SIF and k-Factor Test of Sweeplus®

Volume 3: Design and Analysis ◽

10.1115/pvp2019-93024 ◽

2019 ◽

Author(s):

Yuqing Liu ◽

Ismat El Jaouhari ◽

Philip Diwakar ◽

Dan Lin

Keyword(s):

High Frequency ◽

Thermal Loading ◽

Low Frequency ◽

Flow Induced Vibration ◽

Test Fixture ◽

Labview Software ◽

K Factor ◽

Piping Systems ◽

Out Of Plane ◽

Vibration Parameters

Abstract Formerly, an entire catalogue of 90 deg. branch connections called Sweeplus® was developed and accessed to mitigate acoustic induced vibration (AIV) in piping systems exposed to high frequency vibration. Parameters related to cyclic loading was completed on the Sweeplus® fitting to determine the stress intensification factor (SIF) and flexibility factor (k-factor), in accordance with the latest revision of ASME B31J-2017 code and reported in this paper. A Sweeplus® fitting was welded in a Markl test fixture and controlled through LabView software. The testing configuration and equipment were those used in Kahn test reported in WRC 329. K-factor tests were conducted for the in-plane thru both branch and header piping, and the out-of-plane thru branch. SIF tests were performed in the out-of-plane thru branch. The tests confirmed the SIF of Sweeplus® is less than one which means the fatigue life of Sweeplus® is significantly extended, not only under high frequency AIV excitation, but also under low frequency flow induced vibration (FIV) and thermal loading.

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Experiment on the Effect of Superficial Gas-Liquid Velocities on Slug Flow-Induced Vibration in an Inclined Sagged Riser

Volume 8: CFD and FSI ◽

10.1115/omae2020-18034 ◽

2020 ◽

Cited By ~ 1

Author(s):

Bowen Ma ◽

Narakorn Srinil ◽

Hongjun Zhu ◽

Yue Gao

Keyword(s):

Slug Flow ◽

High Speed ◽

Liquid Velocity ◽

Flow Characteristics ◽

Flow Patterns ◽

Small Scale ◽

Flow Induced Vibration ◽

Pressure Transducers ◽

Test Loop ◽

Flow Features

Abstract Subsea liquid-gas flows conveyed through a flexible riser or pipeline may develop into various flow patterns including slug flow. In this study, the slug flow-induced vibration (SIV) of an inclined sagged riser conveying upward air-water flows is experimentally investigated. A small-scale experiment is carried out in an air-water test loop with a section of a free-hanging catenary tube made of silica gel. Attention is placed on the effect of superficial gas and liquid velocities on SIV responses. Both pipe motions and flow patterns are recorded using non-intrusive high-speed cameras. Pressure variations are also measured at the pipe inlet and outlet by two pressure transducers. The SIV system is tested by employing different ratios of the superficial gas-liquid velocities. Occurrence of unstable slug flows is captured at the relatively high gas-to-liquid velocity ratios, leading to a large-amplitude SIV. Experimental results of the space-time varying riser responses and oscillation frequencies are reported together with the associated slug flow features. Depending on the gas-liquid superficial velocities, slug flow characteristics are observed to vary significantly. These entail an intermittent SIV with modulated amplitudes and frequencies along riser span, signalling a potential dynamic stress and fatigue-related concern. In all experimental cases, the riser responses are found to be multi-modal and dominated by the fundamental planar mode whereas an out-of-plane vibration is negligible. Experimental observations suggest the key interrelationships of the two-fluid flow conditions, the slug characteristics and the pipe dynamics. This finding is meaningful for a practical design of riser transporting internal multiphase flows.

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