Modelling and Analysis of Vortex-Induced Vibrations for Flexible Cylinders Conveying Two-Phase Slug Flows
Bibliographic record
Abstract
Hydrocarbon flows in a marine riser may appear in multiple phases with varying flow patterns, among which, slug flows are known to exhibit complex flow characteristics due to fluctuations in multiphase mass, velocities, and pressure changes.This flow regime can therefore cause significant vibrations and cyclic stresses on the pipeline.The fatigue life of a marine riser can also be significantly reduced when subjected to external excitations due to vortex-induced vibrations (VIV).Bulk of the literatures concerning two-phase flow induced vibrations have largely focused on the use of a simplified linearized tensioned beam model.Fundamental understanding of the vibration phenomena in three-dimensional space and time considering geometric and hydrodynamic non-linearities is still lacking.In this study, a long flexible cylinder subjected to external excitations by vortex-induced vibrations (VIV) in combination with internal slug flow-induced vibrations (SIV) is investigated.A three-dimensional semi-empirical model is presented which comprises of nonlinear structural equations of coupled cross-flow, in-line and axial motions along with equations involving centrifugal force and Coriolis force capable of predicting vibrations due to hydrodynamic slug flow.The model describes variations in lift and drag coefficients using two coupled wake oscillator models and is capable of capturing mass variations in the slug-flow regime.A numerical space-time finite difference approach in conjunction with frequency domain and modal analysis is used for analysing the highly non-linear partial differential equations.The presented model is validated through comparisons with published experimental results pertaining to internal SIV and external VIV for horizontal and vertical pipes.Similar trends in modal participation and oscillation amplitudes were observed in the validation results, indicating that the model has quantitative similarities with published experimental results for both VIV and SIV.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".