Structural Response and Wake Vortex Dynamics of Cylindrical Structures Undergoing VIV with Elliptic Trajectories
Bibliographic record
Abstract
Vortex Induced Vibrations (VIV) of a pivoted circular cylinder were examined through experiments conducted in a water tunnel facility at the University of Calgary. The structural response and wake dynamics of the system were evaluated with the goal of quantitatively describing the attendant fluid-structure interaction. Experiments were performed at a fixed Reynolds number of 3100, a mass ratio of 10.8, and a range of reduced velocities, 4.42<U*<9.05. Laser based displacement sensors and time-resolved, two-component particle image velocimetry (PIV) measurements were used to quantify the structural response and flow development, respectively. The results provide new insight into the fluid-structure interaction for pivoted cylinders, which is of practical engineering interest as this phenomenon is encountered in various civil structures and mechanical devices. \n \nFor the investigated conditions, the cylinder traces elliptic trajectories, with the experimental conditions producing three out of four possible combinations of orbiting direction and primary axis alignment relative to the incoming flow. The study focuses on the quantitative analysis of wake topology and its relation to this type of structural response. The planar phase-averaged wake topology generally agrees with the Morse and Williamson shedding map for one-degree-of-freedom vortex induced vibrations, with 2S, 2P0, and 2P shedding patterns observed within the range of reduced velocities studied here. A new Eulerian vortex identification, tracking, and strength quantification methodology is developed and applied to analyze the vortex shedding process. In the case of 2S vortex shedding, vortices are shed when the cylinder is approaching the maximum transverse displacement and reaches the streamwise equilibrium. 2P vortices are shed approximately half a period earlier in the cylinder's elliptic trajectory. Leading vortices shed immediately after the peak in transverse oscillation and trailing vortices shed near the equilibrium of transverse oscillation. The orientation and direction of the cylinder's elliptic trajectory are shown to influence the timing of vortex shedding, inducing changes in the 2P wake topology. \n \nThree dimensional reconstructions of the phase averaged wake velocity measurements reveal 2S shedding along the span of a stationary cylinder and hybrid shedding for the VIV cases at U*=5.48 and 7.08, with planar wake topology transitioning from 2S to P+S to 2S, and 2S to P+S, respectively. The observed wake topologies show significant deviation from predictions based on the Morse and Williamson shedding map. Examination of the time averaged wake characteristics shows the formation length, wake half-width, and maximum velocity deficit exhibit spanwise trends that support the observed region of wake transition between different shedding regimes. Spectral analysis of the wake velocity indicates cycle-to-cycle variations of the spanwise location of wake topology transition as well as transience in the frequency of vortex shedding.
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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 | 0.000 |
| 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)
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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".