On the Stability of Flows Over Rough Rotating Disks

Harris, J. H.; Thomas, Peter J.; Garrett, S. D.

doi:10.2514/6.2012-3075

Cited by 3 publications

(2 citation statements)

References 26 publications

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“…This could be due to the small values of α * and h * r used in our current simulations. Previous investigations 12,13 of the rotating disk boundary layer have also found only subtle changes in the transition Reynolds number, Re c , for small relative roughness levels.…”

Section: B Rough Wall Rotor-stator Cavitymentioning

confidence: 87%

“…However, in general, there may be situations where the effects of roughness are no longer negligible. For example, Zoueshtiagh et al, 12 and Harris et al, 13 Cooper et al, 14 and Garrett et al 15 conducted investigations into the transition of von Kármán-type boundary layers over rough rotating disks. All investigations agree that surface roughness has only a minor influence on the transition process up to a certain level of roughness, but beyond this, the flow is significantly stabilised via a reduction in the critical Reynolds number Re c for the onset of the dominant Type I mode.…”

Section: Introductionmentioning

confidence: 99%

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The effect of surface roughness on rotor-stator cavity flows

2018

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We are concerned with the CFD simulation of annular rotor-stator cavities using the general purpose second-order finite volume method (FVM) solver OpenFOAM ® and Large Eddy Simulation (LES) methods. Simulations of cavities with smooth surfaces are conducted at various Reynolds numbers, and the properties of the mean turbulent flows are validated against experimental and numerical data available in the literature. Comparisons show that second-order accurate FVM approaches can produce high-fidelity simulations of rotor-stator cavities to an acceptable accuracy and are therefore a viable alternative to the computationally intensive high-order methods. Our validated second-order FVM model is then combined with the parametric force approach of Busse and Sandham ["Parametric forcing approach to rough-wall turbulent channel flow," J. Fluid Mech. 712, 169-202 (2012)] to simulate cavities with a rough rotor surface. Detailed flow visualisations suggest that roughnessinduced disturbances propagate in the downstream direction of the rotor flow toward the outer wall of the cavity. The outer wall subsequently provides a passage to transport said roughness effects from the rough rotor layer to the smooth stator layer. We demonstrate that rotor-stator cavity flows are sensitive to even small roughness levels on the rotor surface alone.

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Section: B Rough Wall Rotor-stator Cavitymentioning

confidence: 87%

Section: Introductionmentioning

confidence: 99%

The effect of surface roughness on rotor-stator cavity flows

2018

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Flows Over Rotating Disks and Cones

Alfredsson,

Kato,

Lingwood

2024

Annu. Rev. Fluid Mech.

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Rotating-disk flows were first considered by von Kármán in a seminal paper in 1921, where boundary layers in general were discussed and, in two of the nine sections, results for the laminar and turbulent boundary layers over a rotating disk were presented. It was not until in 1955 that flow visualization discovered the existence of stationary cross-flow vortices on the disk prior to the transition to turbulence. The rotating disk can be seen as a special case of rotating cones, and recent research has shown that broad cones behave similarly to disks, whereas sharp cones are susceptible to a different type of instability. Here, we provide a review of the major developments since von Kármán's work from 100 years ago, regarding instability, transition, and turbulence in the boundary layers, and we include some analysis not previously published. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 56 is January 2024. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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Turbulence Leads to Overestimation of the Acid-Diffusion Coefficient at Typical Experimental Conditions Using the Rotating Disk Apparatus

Ivanishin

Kotb

Nasr‐El‐Din

2021

Day 1 Mon, December 06, 2021

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A rotating-disk apparatus (RDA) is used to determine the acid-diffusion coefficient. The equations to interpret RDA tests were previously derived assuming laminar flow to the disk, i.e. uniform accessibility with equal flux of the reactive species over the entire surface of the disk. Thus, the acid-diffusion coefficient is overestimated if the tests are run at transition or turbulent flow regimes. The present work validated laminar flow assumptions at typical RDA experimental conditions to optimize the acid-diffusion coefficient measurements. Disks of calcite marble with a diameter of 0.72, 1.11, and 1.46 in. were reacted in an RDA with hydrochloric acid at temperatures ranging from 73.4 to 100°F and disk rotational speeds ranging from 207 to 1,555 rpm. Transition to turbulent flow was observed at Reynolds numbers one order of magnitude lower than the universally accepted critical value of 3×105. Dissolution patterns on the disks after the experiments and the simulation results using a developed computational fluid-dynamics model confirm this conclusion. The turbulence created cavities near the edges of the 1.46 and 1.1 in. disks starting at rotational speeds of 587 and 829 rpm, respectively. The region of turbulent flow propagated toward the center of the disks with further increase of disk rotational speed. Because of the non-uniform (higher) mass-transfer rate, the diffusion coefficient is overestimated to a value of 6.71×10−5 and 5.01×10−5 cm2/s for the 1.46 and 1.11 in. disks, respectively. For the 0.72 in. disks, no turbulent flow was observed at all disk rotational speeds tested, and the calculated value of the diffusion coefficient was 3.08×10-5 cm2/s. Commercial RDA setups are often equipped with 1.0 or 1.5 in. coreholders and are capable of maintaining a disk rotational speed of up to 2,000 rpm. Thus, care must be taken not to run the tests at transition or turbulent flow regimes, as this will result in overestimation of the acid-diffusion coefficient. Preliminary results indicate that the observed phenomena also affect the RDA analysis of organic and other less reactive acid compositions. Presented results are integral for designing the RDA tests to improve the accuracy of the acid-diffusion coefficient calculations.

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On the Stability of Flows Over Rough Rotating Disks

Cited by 3 publications

References 26 publications

The effect of surface roughness on rotor-stator cavity flows

The effect of surface roughness on rotor-stator cavity flows

Flows Over Rotating Disks and Cones

Turbulence Leads to Overestimation of the Acid-Diffusion Coefficient at Typical Experimental Conditions Using the Rotating Disk Apparatus

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