Numerical Investigation of a Rotationally Oscillating Cylinder in Mean Flow

Cheng, M.; Chew, Y. T.; Luo, S. C.

doi:10.1006/jfls.2001.0387

Cited by 50 publications

(32 citation statements)

References 21 publications

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“…experimental work was followed by a series of numerical [22][23][24][25][26][27][28][29][30] and experimental investigations [31][32][33][34]. Recently, due to the maturity of control theory, optimization methods and computational fluid dynamics, optimal and suboptimal approaches attracted increased attention in flow control setting [35][36][37].…”

Section: A Generic Configuration Of Separated Flows: the Cylinder Wakmentioning

confidence: 99%

Optimal control of the cylinder wake in the laminar regime by trust-region methods and POD reduced-order models

Bergmann

Cordier

2008

Journal of Computational Physics

180

154

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In this paper, optimal control theory is used to minimize the total mean drag for a circular cylinder wake flow in the laminar regime (Re = 200). The control parameters are the amplitude and the frequency of the time-harmonic cylinder rotation. In order to reduce the size of the discretized optimality system, a Proper Orthogonal Decomposition (POD) Reduced-Order Model (ROM) is derived to be used as state equation. We then propose to employ the Trust-Region Proper Orthogonal Decomposition (TRPOD) approach, originally introduced by Fahl (2000), to update the reduced-order models during the optimization process. A lot of computational work is saved because the optimization process is now based only on low-fidelity models. A particular care was taken to derive a POD ROM for the pressure and velocity fields with an appropriate balance between model accuracy and robustness. The key enablers are the extension of the POD basis functions to the pressure data, the use of calibration methods for the POD ROM and the addition in the POD expansion of several non-equilibrium modes to describe various operating conditions. When the TRPOD algorithm is applied to the wake flow configuration, this approach converges to the minimum predicted by an open-loop control approach and leads to a relative mean drag reduction of 30% at reduced cost.

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Section: A Generic Configuration Of Separated Flows: the Cylinder Wakmentioning

confidence: 99%

Optimal control of the cylinder wake in the laminar regime by trust-region methods and POD reduced-order models

Bergmann

Cordier

2008

Journal of Computational Physics

180

154

View full text Add to dashboard Cite

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“…The condition of drag reduction is found around the forcing Strouhal number Sf=1, the rotational amplitude Vr=2 at the Reynolds number Re=15,000. The drag reduction rates by numerical simulations reported in literatures are scattered in a wide range 0 -60% at lower Reynolds number Re=1,000-3,000 (Lu and Sato 1996, He et al, 2000, Shiels and Leonard 2001, Cheng et al 2001, Srinivas and Fujisawa 2003. Therefore, the drag reduction at lower Reynolds number is not clear.…”

Section: Introductionmentioning

confidence: 89%

A study on drag reduction of a rotationally oscillating circular cylinder at low Reynolds number

Fujisawa

Ugata

Suzuki

2005

J Vis

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The flow field around a rotationally oscillating circular cylinder in a uniform flow is studied by using a particle image velocimetry to understand the mechanism of drag reduction and the corresponding suppression of vortex shedding in the cylinder wake at low Reynolds number. Experiments are conducted on the flow around the circular cylinder under rotational oscillation at forcing Strouhal number 1, rotational amplitude 2 and Reynolds number 2,000. It is found from the flow measurement by PIV that the width of the wake is narrowed and the velocity fluctuations are reduced by the rotational oscillation of the cylinder, which results in the drag reduction rate of 30%. The mechanism of drag reduction is studied by phase-averaged PIV measurement, which indicates the formation of periodic small-scale vortices from both sides of the cylinder. It is found from the cross-correlation measurement between the velocity fluctuations that the large-scale structure of vortex shedding is almost removed in the cylinder wake, when the small-scale vortices are generated at the unstable frequency of shear layer by the influence of rotational oscillation.

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“…Thus, there is a transition between different vortex shedding modes as the relationship between oscillation frequency and the vortex shedding frequency for the stationary cylinder varies for the same amplitude A . Commonly, some authors present two different flow regimes, being the no lock-in regime and the lock-in regime (Cheng et al 2001a(Cheng et al , 2001b. According to Löhner & Tuszynski (1998), the flow around a rotationally-oscillating cylinder is a forced oscillator form, or a nonlinear system, that in some cases, can become chaotic.…”

Section: Flow Over a Rotationally-oscillating Circular Cylindermentioning

confidence: 99%