The influences of V-shaped ribs and spanwise system rotation on a turbulent square duct flow
Bibliographic record
Abstract
In this thesis, the effects of surface-mounted V-shaped ribs and spanwise system rotations on fully-developed turbulent square duct flows were investigated using the particle image velocimetry (PIV) measurement, large-eddy simulation (LES) and direct numerical simulation (DNS). The PIV measurements were conducted in a water channel, and three different angled V-shaped (60°, 45° and 30°) and perpendicular (90°) ribs were considered. As a complement for the PIV experiments, LES was also used to simulate the measured cases under the same experimental conditions. To perform LES, a parallel finite volume method (FVM) code adopting the generalized curvilinear coordinate system was developed. The first- and second-order moments of the turbulence flows obtained from LES were validated against the PIV measurement data. Both the PIV and LES results showed that strong secondary flows in the pattern of a pair of counter-rotating streamwise-elongated vortices exist in all three V-shaped rib cases. The impacts of rib geometry on turbulent coherent structures were investigated using vortex identifiers, temporal autocorrections, spatial two-point autocorrelations, and velocity spectra. To study the effects of system rotations on turbulent square duct flows, DNS was performed for the turbulent flows confined within a square duct subjected to at a wide range of spanwise system rotations. The DNS was conducted using a modified open-source parallel spectral-element method (SEM) code. The influences on turbulent duct flows by the system rotation were investigated by analyzing the transport equations of Reynolds stresses and vorticity correlations. Turbulent structures under different system rotations were also systematically studied using the energy spectra, autocorrelations of vorticity fluctuations, and linear stochastic estimation. It was observed that in response to the system rotation, secondary flows appear as streamwise counter-rotating vortices. At sufficiently high rotation numbers, a Taylor-Proudman region appears and complete laminarization is almost reached near the top and sidewalls. It was also observed that the Coriolis force dominates the transport of Reynolds stresses and turbulent kinetic energy, and forces the spectra of streamwise and vertical velocities to synchronize within a wide range of streamwise length scales.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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)
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".