Scaling Considerations for Fluidic Oscillator Flow Control on the Square-back Ahmed Vehicle Model

Metka, Matthew; Gregory, James W.; Sassoon, Aaron M.; McKillen, James

doi:10.4271/2015-01-1561

Cited by 13 publications

(5 citation statements)

References 12 publications

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“…1, the length of the mixing chamber (L mc ) is defined as the horizontal distance between the Coanda surface leading edge and the feedback channel inlet corner. It is well-documented (Metka 2015;Seo et al 2018) that L mc plays a crucial role in the determination of the oscillation frequency of the SWJ. Since, in our case L mc is constant, any modifications of the oscillation frequencies of D 2 geometries must originate elsewhere.…”

Section: Actuator Geometriesmentioning

confidence: 99%

“…Bobusch et al (2013b) and Seo et al (2018) demonstrated that the feedback channel length and height have little effect on the oscillation frequency, but do affect the oscillation amplitude and periodicity. On the other hand, the variation in the length of the mixing chamber significantly affects the jet oscillation frequency, where frequency scales as 1 L 2 (Metka et al 2015). More recently, Park et al (2020) have similarly characterized the actuator flow in a supersonic regime, using Taguchi's Design of Experiment to perform a systematic exploration of the impact of several key geometric parameters.…”

Section: Introductionmentioning

confidence: 99%

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Sensitivity of a fluidic oscillator to modifications of feedback channel and mixing chamber geometry

2021

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This experimental study investigates the effects of internal geometry modifications on the performance of a curved Sweeping Jet actuator. The modifications are applied to the geometry of the feedback channel and the mixing chamber Coanda surface, and the resulting actuator properties are evaluated using time-resolved static pressure measurements inside the actuator and hot-wire measurements of the external flow. The major result is that small, localized modifications of the curved sweeping jet actuator geometry can lead to a complete change in the external flow regime, making the jet velocity distribution homogeneous, similar to the angled variant of the actuator. The Coanda surface shape is identified as the primary cause of the external jet adopting the bifurcated or homogeneous flow regime. The relationships between the sweeping frequency, jet deflection angle, required supply pressure, and pressure fluctuations are analyzed and discussed in detail. External flow behavior and coherence are characterized by phase-averaged, phase-locked velocity profiles and auto-correlation of the velocity signals. Graphical abstract

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Section: Actuator Geometriesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Sensitivity of a fluidic oscillator to modifications of feedback channel and mixing chamber geometry

2021

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“…From their applications in flow control, it is interesting to mention their use in combustion control [3], flow deflection and mixing enhancement [4], flow separation modification in airfoils [5], boundary layer modification on hump diffusers used in turbomachinery [6], flow separation control on compressors stator vanes [7], gas turbine cooling [8], drag reduction on lorries [9], and noise reduction in cavities [10].Despite the existence of particular fluidic oscillator configurations, like the one introduced by Uzol and Camci [11], which was based on two elliptical cross-sections placed transversally and an afterbody located in front of them, or the one proposed by Huang and Chang [12], which was a V-shaped fluidic oscillator, most of the recent studies on oscillators focused on two main, very similar, canonical geometries, which Ostermann et al [13] called the angled and the curved oscillator geometries. Some very recent studies on the angled geometry are [13][14][15][16][17][18][19][20][21][22][23], while the curved geometry was studied by [4,10,13,[23][24][25][26][27][28][29][30][31][32][33]. Ostermann et al [13], compared both geometries, concluding that the curved one was energetically the most efficient.One of the first analyses of the internal flow on an angled fluidic oscillator was undertaken by Bobusch et al [17].…”

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confidence: 99%

Analysis of the Forces Driving the Oscillations in 3D Fluidic Oscillators

Baghaei

Bergadà

2019

Energies

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One of the main advantages of fluidic oscillators is that they do not have moving parts, which brings high reliability whenever being used in real applications. To use these devices in real applications, it is necessary to evaluate their performance, since each application requires a particular injected fluid momentum and frequency. In this paper, the performance of a given fluidic oscillator is evaluated at different Reynolds numbers via a 3D-computational fluid dynamics (CFD) analysis. The net momentum applied to the incoming jet is compared with the dynamic maximum stagnation pressure in the mixing chamber, to the dynamic output mass flow, to the dynamic feedback channels mass flow, to the pressure acting to both feedback channels outlets, and to the mixing chamber inlet jet oscillation angle. A perfect correlation between these parameters is obtained, therefore indicating the oscillation is triggered by the pressure momentum term applied to the jet at the feedback channels outlets. The paper proves that the stagnation pressure fluctuations appearing at the mixing chamber inclined walls are responsible for the pressure momentum term acting at the feedback channels outlets. Until now it was thought that the oscillations were driven by the mass flow flowing along the feedback channels, however in this paper it is proved that the oscillations are pressure driven. The peak to peak stagnation pressure fluctuations increase with increasing Reynolds number, and so does the pressure momentum term acting onto the mixing chamber inlet incoming jet.Original fluidic oscillators design goes back to the 60 s and 70 s. Their outlet frequency ranges from several Hz to KHz and the flow rate is usually of a few dm 3 /min. From their applications in flow control, it is interesting to mention their use in combustion control [3], flow deflection and mixing enhancement [4], flow separation modification in airfoils [5], boundary layer modification on hump diffusers used in turbomachinery [6], flow separation control on compressors stator vanes [7], gas turbine cooling [8], drag reduction on lorries [9], and noise reduction in cavities [10].Despite the existence of particular fluidic oscillator configurations, like the one introduced by Uzol and Camci [11], which was based on two elliptical cross-sections placed transversally and an afterbody located in front of them, or the one proposed by Huang and Chang [12], which was a V-shaped fluidic oscillator, most of the recent studies on oscillators focused on two main, very similar, canonical geometries, which Ostermann et al. [13] called the angled and the curved oscillator geometries. Some very recent studies on the angled geometry are [13][14][15][16][17][18][19][20][21][22][23], while the curved geometry was studied by [4,10,13,[23][24][25][26][27][28][29][30][31][32][33]. Ostermann et al. [13], compared both geometries, concluding that the curved one was energetically the most efficient.One of the first analyses of the internal flow on an angled fluidic oscillator was undertaken by B...

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“…1 was used to quantify the relative strength of the sweeping jet to the freestream. This parameter has been frequently used in the literature to describe the strength of an actuator with an incoming flow (Metka et al, 2015;Cattafesta and Sheplak, 2011).…”

Section: Effects Of Changing Actuator Strengthmentioning

confidence: 99%

Control of afterbody vortices from a slanted-base cylinder using sweeping jets

et al. 2022

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In this paper, a sweeping jet is applied to control the afterbody vortices behind a slanted-base cylinder for the first time at Reynolds numbers from 87,000 to 200,000. The control effects are examined using stereo Particle Image Velocimetry (PIV) and surface pressure measurements with the jet momentum coefficient (Cμ) varying from 0.056 to 0.893. It is found that the sweeping jet results in increasingly diffused and larger afterbody vortices as Cμ increases. While an increase in Cμ up to 0.167 leads to a reduction in the circulation of the afterbody vortices and their earlier detachment from the slanted base, a further increase in Cμ introduces additional vorticity into the afterbody vortices leading to higher vortex strength, which could be detrimental to the control purpose. The interaction mechanism of sweeping jets lies in that turbulence is injected into the afterbody vortices as the sweeping jet intersects with these vortices and this subsequently causes diffusion of velocity gradient in the vortices which weakens their strength. As the sweeping jet spreads itself sideways while it propagates downstream along the endplate, it pushes the afterbody vortices upwards and to the side. The impact of the sweeping jet has resulted in the dominant vortex wandering frequency of the afterbody vortex being locked to that of the sweeping jet. This also causes the afterbody vortices detach themselves from the endplate earlier resulting in a shorter low-pressure footprint on the surface.

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Scaling Considerations for Fluidic Oscillator Flow Control on the Square-back Ahmed Vehicle Model

Cited by 13 publications

References 12 publications

Sensitivity of a fluidic oscillator to modifications of feedback channel and mixing chamber geometry

Sensitivity of a fluidic oscillator to modifications of feedback channel and mixing chamber geometry

Analysis of the Forces Driving the Oscillations in 3D Fluidic Oscillators

Control of afterbody vortices from a slanted-base cylinder using sweeping jets

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