Modelling vortex-induced vibrations of branched structures by coupling a 3D-corotational frame finite element formulation with wake-oscillators
Bibliographic record
Abstract
Branched structures are present in a diverse set of problems, from modelling branch pipe connections to simulating tree dynamics.Soft corals like the Bipinnate sea plume, have a branched geometry and are soft enough to bend under the waves.Due to their cylindrical cross section, a vortex street forms in the coral's wake inducing vibrations of its branches.Despite extensive studies on VIV in straight geometries, the three-dimensional (3D) dynamics of flexible branched structures remains uninvestigated.In this numerical and experimental study, we develop a novel formulation for the accurate computation of in-line and cross-flow VIV of frame structures undergoing large deformation.The finite element approach is used to model arbitrarily complex geometries of branched frame structures.Our formulation allows to model complex geometries with forks or sharp angles.The consistent 3D corotational formulation for frame elements computes the internal, inertial and hydrodynamic forces.A wake-oscillator approach models the near wake dynamics with fluctuating fluid forces on the structure in the in-line and cross-flow directions.The drag and lift coefficients follow distributed Van der Pol oscillators.Moreover, we implement the numerical resolution procedure in the open-source library ONSAS.The present formulation and numerical resolution procedure is validated by solving three examples, including comparisons with an analytical solution, a wake-oscillator, and experimental data from the literature.We also conduct experiments of a flexible and elastic cylinder clamped inside a water tunnel under a constant uniform flow.Amplitudes and power spectral density of the tip transverse displacements are compared with the model prediction.Finally, the proposed formulation is applied on a cylinder with two branches.The simulations demonstrate a multi-frequency response with higher amplitudes of displacements when additional branches are incorporated onto the cylinder, emphasizing the significance of considering VIV in nature and engineering applications for such geometries.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 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 source (direct Gemma or distilled Codex), 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".