Journal ArticleDOI
On the spatial structure of global modes in wake flow
TLDR
In this article, a scaling law of the amplitude oscillating with the fundamental frequency corresponding to the maximum of the global mode is found to agree with the Landau model in a range of Reynolds Re numbers larger than in previous studies, and the position of the maximum amplitude of the fundamental modes scales as (Re−Rec)−1/2.Abstract:
Numerical simulations of wake flow behind an equilateral triangular obstacle are presented. The form of global modes and their dependence on the Reynolds number found in this study are in accordance with recent experimental results of Goujon–Durand et al. [Phys. Rev. E 50, 308 (1994)]. A scaling law of the amplitude oscillating with the fundamental frequency corresponding to the maximum of the global mode is found to agree with the Landau model in a range of Reynolds Re numbers larger than in previous studies. The position of the maximum amplitude of the fundamental modes scales as (Re−Rec)−1/2. The amplitude of the second harmonic of the longitudinal component of the velocity as well as the correction to the mean flow have different critical behavior than the velocity components oscillating with fundamental frequency. During linear growth the position of the maximum of the global modes is constant and moves only in the nonlinear regime. The effects of the blockage and the boundary conditions on the side ...read more
Citations
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Journal ArticleDOI
GLOBAL INSTABILITIES IN SPATIALLY DEVELOPING FLOWS: Non-Normality and Nonlinearity
TL;DR: In this paper, the dynamics of open flows are considered as a superposition of linear or nonlinear instability waves that behave at each streamwise station as if the flow were homogeneous in the streamwise direction.
Journal ArticleDOI
Structural sensitivity of the first instability of the cylinder wake
Flavio Giannetti,Paolo Luchini +1 more
TL;DR: In this article, the stability properties of the flow past an infinitely long circular cylinder are studied in the context of linear theory, where an immersed-boundary technique is used to represent the cylinder surface on a Cartesian mesh.
Journal ArticleDOI
Closed-loop control of an open cavity flow using reduced-order models
TL;DR: In this article, a bi-orthogonal projection is introduced to arrive at reduced-order models for the compensated problem, and the open-loop behavior of the full and reduced systems are analysed by comparing the respective transfer functions.
Journal ArticleDOI
Low-dimensional modelling of a transient cylinder wake using double proper orthogonal decomposition
TL;DR: This work introduces a novel extension to the proper orthogonal decomposition (POD) procedure that facilitates mode construction from transient data sets and demonstrates the possibility of constructing accurate dynamic low-dimensional models for feedback control by using unforced and transient forced data only.
References
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Journal ArticleDOI
Local and global instabilities in spatially developing flows
TL;DR: In this article, a review of recent developments in the hydro- dynamic stability theory of spatially developing flows pertaining to absolute/convective and local/global instability concepts is presented.
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On the non-linear mechanics of wave disturbances in stable and unstable parallel flows Part 1. The basic behaviour in plane Poiseuille flow
TL;DR: In this paper, the authors considered the nature of a non-linear, two-dimensional solution of the Navier-Stokes equations when the rate of amplification of the disturbance, at a given wave-number and Reynolds number, is sufficiently small.
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A finite-element study of the onset of vortex shedding in flow past variously shaped bodies
TL;DR: In this paper, the onset of periodic behavior in two-dimensional laminar flow past bodies of various shapes is examined by means of finite-element simulations, and the transition from steady to periodic flow is marked by a Hopf bifurcation, which is located by solving an appropriate extended set of steady-state equations.
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Hot-Wire Investigation of the Wake behind Cylinders at Low Reynolds Numbers
TL;DR: In this paper, a hot-wire technique has been used to measure the regular vortex street pattern behind a cylinder at low Reynolds number, and the important points resulting from the investigation are that the critical Reynolds number at which vortices are shed is 40, and in the range of Reynolds numbers investigated the vortex are not shed directly from the cylinder but appear some distance downstream as an instability of the laminar wake.