On the active feedback control of a swirling flow in a finite-length pipe

Wang, Shixiao; Rusak, Zvi; Taylor, Stephen; Gong, Rui

doi:10.1017/jfm.2013.554

Cited by 4 publications

(4 citation statements)

References 34 publications

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“…It enforces a negative rate of change of the perturbation's energy, the decay of the perturbation and the return of the flow to a columnar state, even at high-Re flow cases where no columnar state exists naturally. This is supported by the linear stability analysis of the flow control problem in Wang et al (2013), which showed that all modes of perturbations are stabilized for a wide range of swirl up to 50 % above ω 1 . Moreover, when the initial perturbation is large, a sufficiently large γ may overcome the steepening effect from the nonlinear term and enforce the decay of the perturbation and establishment of a columnar state.…”

Section: Insight Into Flow Dynamics and Controlmentioning

confidence: 68%

“…(d) All the numerical examples shown in this paper clarify for the first time the feasibility of the proposed control approach. Without a full simulation that is also supported by the present weakly nonlinear control problem, there is no evidence or proof that the control approach derived from the linear theory of Wang et al (2013) works for large perturbations and at swirl levels far away from the critical swirl. The present paper undertakes this challenging problem and explores the efficiency of the proposed control approach.…”

mentioning

confidence: 76%

“…The main objective is to control the nominally axisymmetric core flow and enforce flow stabilization on a columnar concentrated vortex state. This approach extends the preliminary studies of swirling flow control in Rusak et al (2012) and Wang, Rusak, Taylor & Gong (2013). In order to achieve this objective, we need to determine a control law that will cut the feed-forward instability mechanism, robustly suppress the fast nonlinear dynamics of perturbations at above-critical states (ω > ω 0 ), and establish a columnar state with a wide basin of attraction in response to large-amplitude perturbations at various swirl levels.…”

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confidence: 98%

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An active feedback flow control theory of the axisymmetric vortex breakdown process

2015

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An active feedback flow control theory of the axisymmetric vortex breakdown process in incompressible swirling flows in a finite-length straight circular pipe is developed. Flow injection distributed along the pipe wall is used as the controller. The flow is subjected to non-periodic inlet and outlet conditions where the inlet profiles of the axial velocity, circumferential velocity and azimuthal vorticity are prescribed, along with no radial velocity at the outlet. A long-wave asymptotic analysis at near-critical swirl ratios, which involves a rescaling of the axial distance and time, results in a model problem for the dynamics and the nonlinear control of both inviscid and highReynolds-number (Re) flows. The approach provides the bifurcation diagram of steady states and the stability characteristics of these states. In addition, an energy analysis of the controlled flow dynamics suggests a feedback control law that relates the flow injection to the evolving maximum radial velocity at the inlet. Computed examples of the flow dynamics based on the full Euler and Navier-Stokes formulations at various swirl levels demonstrate the evolution to near-steady breakdown states when swirl is above a critical level that depends on Re. Moreover, applying the proposed feedback control law during flow evolution shows for the first time the successful and robust elimination of the breakdown states and flow stabilization on an almost columnar state for a wide range of swirl (up to at least 30 %) above critical. The feedback control cuts the natural feed-forward mechanism of the breakdown process. Specifically, in the case of high-Re flows, the control approach establishes a branch of columnar states for all swirl levels studied, where in the natural flow dynamics no such states exist. The present theory is limited to the control of axisymmetric flows in pipes where the wall boundary layer is thin and attached and does not interact with the flow in the bulk.

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Section: Insight Into Flow Dynamics and Controlmentioning

confidence: 68%

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confidence: 76%

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confidence: 98%

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An active feedback flow control theory of the axisymmetric vortex breakdown process

2015

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“…Comprehensive studies on this subject can be found in the monographs by Anagnostopoulos (2002) and Naudscher and Rockwell (1994). The vortex-induced vibration (VIV) problem of elastically-mounted cylinders has also received much attention from the fluid mechanicians and offshore designers to avoid catastrophes due to the resulting oscillations (Feng and Wang, 2010; Marquet et al., 2008; Wang et al., 2013).…”

Section: Introductionmentioning

confidence: 99%

Vortex-induced vibration analysis of viscoelastically mounted rigid circular cylinders in cross-flow at a moderate Reynolds number

Lima

Cunha

Silva

et al. 2017

Journal of Vibration and Control

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The vortex-induced vibrations may have disastrous effects in engineering practice, affecting significantly the durability, reliability and safety of engineering structures. This is a reason for which a great deal of effort has been dedicated to the proposition of control strategies to deal with the vortex-induced vibration problem. However, few works have proposed the use of viscoelastic materials to suppress the vibrations induced by vortex shedding, which motivates the present study. Here, the immersed boundary method combined with the virtual physical model is used to investigate the dynamics of a viscoelastically-mounted rigid cylinder in a fluid flow under transverse oscillations induced by vortex shedding. A straightforward time-domain modeling procedure of immersed viscoelastic system by using a four-parameter fractional derivative model is proposed. After the theoretical aspects, numerical tests are performed to investigate the vortex-induced oscillations and flow characteristics of the immersed viscoelastic system at Reynolds number 10,000 for a range of reduced velocity and temperature for two values of mass ratios. The results demonstrate the interest in using viscoelastic materials to mitigate the vortex-induced vibrations.

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On the three-dimensional stability of a solid-body rotation flow in a finite-length rotating pipe

et al. 2016

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The three-dimensional, inviscid and viscous flow instability modes that appear on a solid-body rotation flow in a finite-length straight, circular pipe are analysed. This study is a direct extension of the Wang & Rusak (Phys. Fluids, vol. 8 (4), 1996a, pp. 1007–1016) analysis of axisymmetric instabilities on inviscid swirling flows in a pipe. The linear stability equations are the same as those derived by Kelvin (Phil. Mag., vol. 10, 1880, pp. 155–168). However, we study a general mode of perturbation that satisfies the inlet, outlet and wall conditions of a flow in a finite-length pipe with a fixed in time and in space vortex generator ahead of it. This mode is different from the classical normal mode of perturbations. The eigenvalue problem for the growth rate and the shape of the perturbations for any azimuthal wavenumber $m$ consists of a linear system of partial differential equations in terms of the axial and radial coordinates ($x,r$). The stability problem is solved numerically for all azimuthal wavenumbers $m$. The computed growth rates and the related shapes of the various perturbation modes that appear in sequence as a function of the base flow swirl ratio (${\it\omega}$) and pipe length ($L$) are presented. In the inviscid flow case, the $m=1$ modes are the first to become unstable as the swirl ratio is increased and dominate the perturbation’s growth in a certain range of swirl levels. The $m=1$ instability modes compete with the axisymmetric ($m=0$) instability modes as the swirl ratio is further increased. In the viscous flow case, the viscous damping effects reduce the modes’ growth rates. The neutral stability line is presented in a Reynolds number ($Re$) versus swirl ratio (${\it\omega}$) diagram and can be used to predict the first appearance of axisymmetric or spiral instabilities as a function of $Re$ and $L$. We use the Reynolds–Orr equation to analyse the various production terms of the perturbation’s kinetic energy and establish the elimination of the flow axial homogeneity at high swirl levels as the underlying physical mechanism that leads to flow exchange of stability and to the appearance of both spiral and axisymmetric instabilities. The viscous effects in the bulk have only a passive influence on the modes’ shapes and growth rates. These effects decrease with the increase of $Re$. We show that the inviscid flow stability results are the inviscid-limit stability results of high-$Re$ rotating flows.

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On the active feedback control of a swirling flow in a finite-length pipe

Cited by 4 publications

References 34 publications

An active feedback flow control theory of the axisymmetric vortex breakdown process

An active feedback flow control theory of the axisymmetric vortex breakdown process

Vortex-induced vibration analysis of viscoelastically mounted rigid circular cylinders in cross-flow at a moderate Reynolds number

On the three-dimensional stability of a solid-body rotation flow in a finite-length rotating pipe

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