Non-uniform suction control of flow around a circular cylinder

Ramsay, James; Sellier, Mathieu; Ho, Wei Hua

doi:10.1016/j.ijheatfluidflow.2020.108559

Cited by 9 publications

(6 citation statements)

References 27 publications

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“…This method of flow control has been studied widely during the 20 th Century, and continues to be investigated and developed today. One important finding from this research is that non-uniform suction profiles are usually much more efficient and effective than uniform or simple slot suction [2]. For example, optimisation studies where any profile of suction/blowing on the surface of a cylinder is permitted found the profiles that best reduced drag were non-uniform and distributed over the cylinder surface [3].…”

Section: Introductionmentioning

confidence: 86%

Designing Suction-Inducing Geometries for Flow Control using CFD-Coupled Artificial Neural Networks

Ramsay¹,

Sellier²,

Ho³

2020

Australasian Fluid Mechanics Conference (AFMC)

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Suction of the boundary layer is an effective method of flow control, but it often requires too much energy to be worthwhile. Using pressure gradients inherent in the flow to generate the suction eliminates this efficiency issue. Designing geometries to achieve this is difficult, however. In this study we train an artificial neural network to aid the process. A toy problem was investigated of a straight channel divided by a porous medium. The geometry of the upper wall is modified to induce a spanwise 'suction' through the porous medium. The task of the network is to design the geometry of this upper wall so that the desired suction profile is produced. Training data was generated using numerical simulations. The network proved effective at generating geometries that resulted in close approximations to the desired suction profiles. This is a good first step toward fully autogenous suction flow control.

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Section: Introductionmentioning

confidence: 86%

Designing Suction-Inducing Geometries for Flow Control using CFD-Coupled Artificial Neural Networks

Ramsay¹,

Sellier²,

Ho³

2020

Australasian Fluid Mechanics Conference (AFMC)

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“…The geometry for the numerical simulations can be found in Figure 1(a). The domain was based on that used by Wu et al for the numerical portion of their paper and has also been used successfully by the present authors [21,29]. The dimensions are dictated by the diameter of the cylinder, D = 0:1 m. Not visible in the figure is a circular curve with diameter 1:0002D concentric with the cylinder.…”

Section: Model and Numerical Methodsmentioning

confidence: 99%

“…This implies two important conclusions: (1) the location of the suction (angle of suction) is of critical importance in the effectiveness of control and (2) the control must be set up to account for this. Indeed, other investigations have verified the importance of the location of suction for delaying separation on the circular cylinder, including the fact that this is dependent on the Reynolds number [29]. Consequently, an ideal control that will be effective over a range of Re must be able to account for the changing location of optimal suction.…”

Section: International Journal Of Aerospace Engineeringmentioning

confidence: 97%

Eliminating Boundary Layer Separation on a Cylinder with Nonuniform Suction

Ramsay

Sellier

2020

International Journal of Aerospace Engineering

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Boundary layer separation negatively influences the performance of aerospace vehicles, for example, by triggering static stall or reducing combustion engine efficiency. Developing effective flow control to delay or eliminate separation is therefore of real use to the field. In this paper, numerical studies were carried out to optimise distributed suction profiles for preventing boundary layer separation on a circular cylinder in the fully laminar regime (Re<188), with the least control effort. Relationships were found between the Reynolds number, the separation angle of the uncontrolled case, and the uniform suction needed to eliminate separation. It was found that for Re>20, the uniform suction required to eliminate separation followed a quadratic profile, as a function of Re. Maximum uniform suction effort was needed at Re=20, requiring a suction coefficient of CQ=49.14 (as a percentage of the free-stream velocity) to eliminate separation. To resolve the best nonuniform suction profile at Re=180, a variety of optimisation studies were performed using the coordinate search method. It was determined that the use of six control segments on each half of the cylinder provided the best control and efficient convergence to the optimal solution. 6-segment nonuniform suction eliminated separation at Re=180 with net suction effort of CQ=13.26 compared to CQ=31.25 for the uniform case. These optimal suction profiles were compared using time-dependent simulations to confirm that both methods eliminate separation when introduced to an already unsteady case. Nonuniform suction eliminated separation faster, though uniform suction was more stable.

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“…Maintenance of airway and improvement of oxygenation in patients are achievable through oral suctioning (Propp and Gillis, [38]). In fact, less invisible separation that do occur between the boundary layer can be eliminated by either nonuniform or uniform suction but non-uniform suction is more efficient; Ramsay et al [39]. In fluid dynamics, most especially analysis of boundary layer flows, this has led to the modeling of suction at the wall as v(x=0, y)=v w where v w is the suction velocity.…”

Section: Mathematical Formulationmentioning

confidence: 99%

Significance of suction and dual stretching on the dynamics of various hybrid nanofluids: Comparative analysis between type I and type II models

et al. 2020

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The transport phenomenon involving a thorough mixture of a base fluid and any two different types of nanoparticles (i.e. hybrid nanofluid) has attracted the attention of scientists to deliberate on the significance and performance of such fluid using two different types of thermo-physical models (i.e. type I and type II). This study examines the dynamics of hybrid nanofluids using type I and type II hybrid models with major emphasis on the difference. Also, this report unravels the significance of suction and dual stretching on the boundary layer flow of hybrid nanofluids. The governing equation that model the dynamics was modeled, non-dimenzionalized, parameterized, and solved numerically. It is concluded that both type I and type II models of viscosity should not be used for volume fraction ϕ1 + ϕ2 > 0.02 as both models are found to be the same, accurate but limited. The stretching ratio has dual effects on the velocity in both horizontal directions and temperature distribution decreases with stretching rate. Local skin friction coefficients and temperature distribution are decreasing properties of suction. In the case of various water-based conveying various nanoparticles (seven different hybrid nanofluids), optimal Nusselt number is ascertained at a larger value of stretching ratio and suction in the dynamics of water conveying (less dense nanoparticles) multiple wall CNT and silicon dioxide.

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Non-uniform suction control of flow around a circular cylinder

Cited by 9 publications

References 27 publications

Designing Suction-Inducing Geometries for Flow Control using CFD-Coupled Artificial Neural Networks

Designing Suction-Inducing Geometries for Flow Control using CFD-Coupled Artificial Neural Networks

Eliminating Boundary Layer Separation on a Cylinder with Nonuniform Suction

Significance of suction and dual stretching on the dynamics of various hybrid nanofluids: Comparative analysis between type I and type II models

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