An Experimental Study of a Rotating-Disk Turbulent Boundary-Layer Flow

Imayama, Shintaro; Lingwood, R. J.; Alfredsson, P. Henrik

doi:10.1007/978-3-319-01860-7_27

Cited by 5 publications

(7 citation statements)

References 6 publications

(6 reference statements)

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“…The correspondence in transition location between simulations and experiments can be seen for larger r where the low-amplitude case A1 is close to Exp c . Relating the forcing amplitude and surface roughness between these two cases, a f = 0.04, which is translated in figure 8(a) to be disturbing the flow of the order of 10 −6 , corresponds to a surface roughness of less than 1 µm (Imayama 2012). However the noise level in the experiments is too high to show the initial growth of the disturbance.…”

Section: Overall Transition Scenariomentioning

confidence: 93%

Transition to turbulence in the rotating-disk boundary-layer flow with stationary vortices

et al. 2017

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This paper proposes a resolution to the conundrum of the roles of convective and absolute instability in transition of the rotating-disk boundary layer. It also draws some comparison with swept-wing flows. Direct numerical simulations based on the incompressible Navier–Stokes equations of the flow over the surface of a rotating disk with modelled roughness elements are presented. The rotating-disk flow has been of particular interest for stability and transition research since the work by Lingwood (J. Fluid Mech., vol. 299, 1995, pp. 17–33) where an absolute instability was found. Here stationary disturbances develop from roughness elements on the disk and are followed from the linear stage, growing to saturation and finally transitioning to turbulence. Several simulations are presented with varying disturbance amplitudes. The lowest amplitude corresponds approximately to the experiment by Imayama et al. (J. Fluid Mech., vol. 745, 2014a, pp. 132–163). For all cases, the primary instability was found to be convectively unstable, and secondary modes were found to be triggered spontaneously while the flow was developing. The secondary modes further stayed within the domain, and an explanation for this is a proposed globally unstable secondary instability. For the low-amplitude roughness cases, the disturbances propagate beyond the threshold for secondary global instability before becoming turbulent, and for the high-amplitude roughness cases the transition scenario gives a turbulent flow directly at the critical Reynolds number for the secondary global instability. These results correspond to the theory of Pier (J. Engng Maths, vol. 57, 2007, pp. 237–251) predicting a secondary absolute instability. In our simulations, high temporal frequencies were found to grow with a large amplification rate where the secondary global instability occurred. For smaller radial positions, low-frequency secondary instabilities were observed, tripped by the global instability.

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Section: Overall Transition Scenariomentioning

confidence: 93%

Transition to turbulence in the rotating-disk boundary-layer flow with stationary vortices

et al. 2017

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“…Further details of the driving system and data acquisition can be found in Refs. [20,21]. Compared with Refs.…”

Section: Experimental Set-upmentioning

confidence: 99%

“…Compared with Refs. [20,21], two changes were made when the disk was replaced by the cone: (a) the traversing system was separated from the driving system and was placed directly on the laboratory floor; and (b) some electrical changes to the electrical configuration were made (introducing ferrite cores and shielding the cables). These changes improved the noise-signal ratio and helped to better resolve the early development of the flow instability when the amplitudes were low.…”

Section: Experimental Set-upmentioning

confidence: 99%

Investigation of the structures in the unstable rotating-cone boundary layer

et al. 2019

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This work reports on the unstable region and the transition process of the boundary-layer flow induced by a rotating cone with a half apex angle of 60 degrees using the probability density function (PDF) contour map of the azimuthal velocity fluctuation, which was first used by Imayama et al. [Phys. Fluids 24, 031701 (2012)] for the similar boundary-layer flow induced by a rotating disk. The PDF shows that the transition behavior of the rotatingcone flow is similar to that on the rotating disk. The effects of roughness elements on the cone surface have been examined. For the cone with roughnesses, we reconstructed the most probable vortex structure within the boundary layer from the hot-wire anemometry time signals. The results show that the PDF clearly describes the overturning process of the high-momentum upwelling of the spiral vortices, which due to vortex meandering cannot be detected in the phase-averaged velocity field reconstructed from the point measurements. At a late stage of the overturning process, our hot-wire measurements captured high-frequency oscillations, which may be related to secondary instability.

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“…Solutions to the equations that describe the velocity distribution throughout the body of the viscous fluid are reported in Schlichting (), and solutes concentration profiles, DBL thicknesses, and molecular diffusion fluxes above a rotating disk were derived and reported in the pioneering work of Levich (). It is not our intent here to review this theory; instead we refer the reader to the numerous previous studies in which mathematical descriptions and solutions to the rotating‐disk hydrodynamics are provided (Levich ; Brady and Durlofsky ; Chang and Abbad ; Imayama ).…”

Section: Materials and Proceduresmentioning

confidence: 99%

Controlling the diffusive boundary layer thickness above the sediment–water interface in a thermostated rotating‐disk reactor

Sulpis

Mucci

Boudreau³

et al. 2019

Limnology & Ocean Methods

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The diffusive boundary layer (DBL) is a thin layer of fluid at the interface with a solid surface in which frictional forces cause molecular diffusion to become the dominant mode of solute transport. The thickness of the DBL is a function of the nature and roughness of sediment substrates, as well as the bottom‐current speed. In low‐energy natural aquatic environments, such as abyssal plains or lakes, the thickness of the DBL can reach several millimeters and significantly impede the diffusive rate of solutes through the sediment–water interface (SWI). Thus, precisely reproducing the DBL in the laboratory is required to simulate benthic diffusive fluxes similar to those encountered in situ. Yet, an experimental apparatus allowing precise control of the DBL thickness at the SWI in the laboratory has not been described in the literature. Here, we present a simple temperature‐controlled rotating‐disk system, which is suitable for the use with natural sediments and that is capable of generating thick DBLs. Water overlying the rotating sediment can be sampled discretely or continuously to monitor the chemical reaction progress. We tested the validity of the reactor by dissolving a foraminiferal sand bed in natural seawater. We find that (1) measured dissolution fluxes agree with those predicted by theory and (2) the dissolution of calcite in these seafloor‐like hydrodynamic conditions is controlled by mass transfer across the DBL above the bed. Guidelines for best practices under various experimental conditions, possible future developments, and the theoretical equations to compute the DBL thickness and diffusive fluxes in this reactor are described.

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An Experimental Study of a Rotating-Disk Turbulent Boundary-Layer Flow

Abstract: Abstract. The azimuthal velocity distribution in a turbulent boundary layer (TBL) on a rotating disk is explored using hot-wire anemometry and compared with those of the two-dimensional TBL over a flat plate.

Cited by 5 publications

References 6 publications

Transition to turbulence in the rotating-disk boundary-layer flow with stationary vortices

Transition to turbulence in the rotating-disk boundary-layer flow with stationary vortices

Investigation of the structures in the unstable rotating-cone boundary layer

Controlling the diffusive boundary layer thickness above the sediment–water interface in a thermostated rotating‐disk reactor

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