“…1 that the maximumgrowth-rate curves (solid lines) obtained from spatial stability analysis break off nearly at R = 420; the broken lines from temporal theory show no singular behavior in the range of Reynolds numbers concerned. 4) This result indicates the appearance of singular points in the region of larger Reynolds numbers of rotating-disk flow, in accordance with the previous studies. 3,5) In this paper, therefore, attention is directed to the flow on a rotating disk, and investigation is made about whether absolute instability can occur in this three-dimensional flow.…”
Section: Introductionsupporting
confidence: 92%
“…As is well c 2001 The Japan Society for Aeronautical and Space Sciences known, the classical spatial theory of linear stability assigns real values of ω and β and determines a complex value of α, whose imaginary part α i indicates spatial damping rate in the positive X direction. The maximum-growth-rate curves then consist of disturbance components satisfying the relations 4) and will have an infinite gradient at the singular point where another condition…”
Rotating-disk flow is taken as a typical example of three-dimensional boundary layers. Numerical computations of localized disturbances according to the propagation theory given in Part 1 are made with a simplified system of stability equations to show if the conditions of absolute instability can be satisfied in this simple flow. The results indicate no such particular amplification of disturbances near a zero of the complex group velocity. It is also shown how initially localized disturbances propagate and develop into quite a large amplification of some limited wave-number components at a downstream station.
“…1 that the maximumgrowth-rate curves (solid lines) obtained from spatial stability analysis break off nearly at R = 420; the broken lines from temporal theory show no singular behavior in the range of Reynolds numbers concerned. 4) This result indicates the appearance of singular points in the region of larger Reynolds numbers of rotating-disk flow, in accordance with the previous studies. 3,5) In this paper, therefore, attention is directed to the flow on a rotating disk, and investigation is made about whether absolute instability can occur in this three-dimensional flow.…”
Section: Introductionsupporting
confidence: 92%
“…As is well c 2001 The Japan Society for Aeronautical and Space Sciences known, the classical spatial theory of linear stability assigns real values of ω and β and determines a complex value of α, whose imaginary part α i indicates spatial damping rate in the positive X direction. The maximum-growth-rate curves then consist of disturbance components satisfying the relations 4) and will have an infinite gradient at the singular point where another condition…”
Rotating-disk flow is taken as a typical example of three-dimensional boundary layers. Numerical computations of localized disturbances according to the propagation theory given in Part 1 are made with a simplified system of stability equations to show if the conditions of absolute instability can be satisfied in this simple flow. The results indicate no such particular amplification of disturbances near a zero of the complex group velocity. It is also shown how initially localized disturbances propagate and develop into quite a large amplification of some limited wave-number components at a downstream station.
“…A comparison of the neutral curves of the parallel-flow theory 15) and those in this figure confirms again that the existence of curvature terms in the stability equations makes it possible to describe the S-C mode belonging to centrifugal instability.…”
Section: Eigenvalue Problems For Multiple Instabilitiessupporting
confidence: 71%
“…6 as 258 and 50.6, respectively, which are slightly lower than the values R c ¼ 290, 282 and 284 for C-F mode given by Lingwood, 11) Itoh 12) and Pier, 13) and R c ¼ 69, 64 and 63 for the S-C mode by Faller,8) Balakumar and Malik 16) and Itoh,12) respectively, as well as the experimentally observed lower limits of C-F mode listed by Malik et al 17) However, the Orr-Sommerfeld equation gives R c ¼ 177 for the C-F mode, 15) which is much lower than the above non-parallel estimations. Since the present study restricts non-parallel terms only to those of the most fundamental activity in the multiple instabilities, it is reasonable that the equations proposed give a critical value midway between the parallel approach and the non-parallel attempts.…”
Section: Eigenvalue Problems For Multiple Instabilitiesmentioning
Instability of the flow on a rotating disk is governed by linearized disturbance equations of the partial differential with respect to the radial distance from the rotation axis and the normal distance from the disk surface. Applying uniform suction from the surface brings a small parameter associated with displacement thickness of the circumferential velocity profile into a dimensionless form of the equation system. Two kinds of series solutions expanded by the powers of this parameter are obtained to describe the cross-flow and centrifugal instabilities of the flow having a twisted velocity profile. The leading terms of the series solutions are determined from two eigenvalue problems of slightly different ordinary differential equations, and the superposition of those equations leads to an eigenvalue problem applicable to multiple-instability characteristics of such three-dimensional boundary layers.
“…More recently, and following the pioneer work of Lingwood [9], Serre et al [11] studied theoretically and numerically the transition from convective to absolute instability of these flows. Experimentally, Savas [12,13] followed by Itoh [14,15] were the first to visualize the different waves occurring in a rotor/stator system. The complete transition diagram was then built by Schouveiler, Le Gal & Chauve [16] as function of the ratio h/δ of the cavity and of the Reynolds number Re = ΩR 2 /ν (R being the radius of the disk).…”
This experimental study is devoted to the transition to turbulence of the flow confined between a stationary and a rotating disk. Using visualization and video image analysis, we describe the different transitions occurring in the flow as the rotating velocity of the disk is varied. The space-time behavior of the wave patterns is analyzed using the BiOrthogonal Decomposition (BOD) technique. This decomposition of the experimental signals on proper modes permits to project the dynamics of the waves in a reduced embedding phase space. By this means, a torus doubling bifurcation is revealed before its complete destruction during the transition to a weak turbulence. Finally, a more classical 2D-Fourier analysis completes our description of the transition and shows for higher rotation rates, the appearance of a more developed turbulence issued from the former chaotic waves.
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