Instabilities and Transition on a Rotating Cone–Old Problems and New Challenges

Kato, Ken; Segalini, Antonio; Alfredsson, P. Henrik; Lingwood, R. J.

doi:10.1007/978-3-030-67902-6_17

Cited by 4 publications

(2 citation statements)

References 10 publications

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“…Previous studies [15], including the ones at high Reynolds number [19], have also shown the existence of two types of short-and longwavelength patterns in the POD modes on a rotating cone of ψ 15°. Recently, Kato et al [23] studied a rotating broad cone (ψ 60°) in still fluid and visualized the instability modes using patterns of the phase-averaged azimuthal velocity. Their visualization also shows short-and long-wavelength patterns.…”

Section: Visualization Of Spiral Vortex Footprintsmentioning

confidence: 99%

Instability of Rotating-Cone Boundary Layer in Axial Inflow: Effect of Cone Angle

et al. 2023

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Boundary-layer instability on a rotating cone induces coherent spiral vortices that are linked to the onset of laminar–turbulent transition. This type of transition is relevant to several aerospace systems with rotating components, e.g., aeroengine nose cones. Because a variety of options exist for the nose-cone shapes, it is important to know how their shape affects the boundary-layer transition phenomena. This study investigates the effect of varying cone angle on the boundary-layer instability on rotating cones facing axial inflow. It is found that increasing cone angle has a stabilizing effect on the boundary layer over rotating cones in axial inflow. The parameter space of Reynolds number [Formula: see text] and local rotational speed ratio [Formula: see text] is experimentally explored to find the spiral vortex growth on rotating cones of half angle [Formula: see text], 45°, and 50°. The previously addressed cases of [Formula: see text] and 30° are also revisited. Increasing half-cone angle is found to have a stabilizing effect on the boundary layer on the rotating cones with [Formula: see text]; i.e., the spiral vortex growth is delayed to higher [Formula: see text] and [Formula: see text]. This effect diminishes when the half-cone angle increases from [Formula: see text] to 50°. The spiral vortex angle [Formula: see text] decreases with increasing rotational speed ratio [Formula: see text] for all the investigated cones, irrespective of the half-cone angle. However, the instability on the broader cones is found to induce shorter azimuthal wavelengths.

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Section: Visualization Of Spiral Vortex Footprintsmentioning

confidence: 99%

Instability of Rotating-Cone Boundary Layer in Axial Inflow: Effect of Cone Angle

et al. 2023

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“…The observed wave number of the stationary cross-flow vortices is smaller than for the disk (a clean 60 • cone typically develops 24 to 26 vortices, compared to 30 to 32 on the disk). Recently non-stationary modes have also been explored by Kato et al (2022).…”

Section: Introductionmentioning

confidence: 99%

Rotating disks and cones a centennial of von Kármán’s 1921 paper

KATO

Lingwood

Alfredsson

2023

JFST

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It is now more than 100 years since the work of von Kármán (1921) on the boundary-layer flow over a rotating disk was published in the first volume of Zeitschrift für Angewandte Mathematik und Mechanik (ZAMM, Vol. 1(4), pp 233-252). Recently, there has been a large amount of work undertaken addressing the instability and transition of the boundary-layer flows over rotating disks and cones using theoretical, numerical and experimental techniques. Here we will discuss some different methods to analyze experimental data that can give insight into the instability and transition to turbulence of boundary-layer flows over rotating slender and broad cones (including the disk). At first, we discuss the pdf-method (probability density function) that allows a simple way to determine regions of instability growth, transition and fully developed turbulence. Secondly, we look at various ways to use spectral information to investigate the boundary layers giving a deeper understanding of the transition process. Finally, a method to determine the most probable flow structure leading up to fully developed turbulence is discussed. We envisage that some of these methods can be useful in analyzing instability and transition also in other flow cases.

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Spiral instability modes on rotating cones in high-Reynolds number axial flow

et al. 2022

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This work shows the behavior of an unstable boundary-layer on rotating cones in high-speed flow conditions: high Reynolds number [Formula: see text], low rotational speed ratio [Formula: see text], and inflow Mach number M = 0.5. These conditions are most-commonly encountered on rotating aeroengine nose cones of transonic cruise aircraft. Although it has been addressed in several past studies, the boundary-layer instability on rotating cones remains to be explored in high-speed inflow regimes. This work uses infrared-thermography with a proper orthogonal decomposition approach to detect instability-induced flow structures by measuring their thermal footprints on rotating cones in high-speed inflow. The observed surface temperature patterns show that the boundary-layer instability induces spiral modes on rotating cones, which closely resemble the thermal footprints of the spiral vortices observed in past studies at low-speed flow conditions: [Formula: see text], S > 1, and [Formula: see text]. Three cones with half-cone angles [Formula: see text], and [Formula: see text] are tested. For a given cone, the Reynolds number relating to the maximum amplification of the spiral vortices is found to follow an exponential relation with the rotational speed ratio S, extending from the low- to high-speed regime. At a given rotational speed ratio S, the spiral vortex angle appears to be as expected from the low-speed studies, irrespective of the half-cone angle.

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Instabilities and Transition on a Rotating Cone–Old Problems and New Challenges

Cited by 4 publications

References 10 publications

Instability of Rotating-Cone Boundary Layer in Axial Inflow: Effect of Cone Angle

Instability of Rotating-Cone Boundary Layer in Axial Inflow: Effect of Cone Angle

Rotating disks and cones a centennial of von Kármán’s 1921 paper

Spiral instability modes on rotating cones in high-Reynolds number axial flow

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