Flow dynamics of a fluidic oscillator with internal geometry variations

Wen, Xin; Li, Ziyan; Zhou, Luanliang; Yu, Chengji; Zubair, Muhammad; Liu, Yudan; Wang, Shiqi; Liu, Yingzheng

doi:10.1063/5.0012471

Cited by 32 publications

(10 citation statements)

References 39 publications

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“…For this design, the distance between two opposing Coanda surfaces is curtailed substantially. Wen et al (2020) reported that by reducing the distance between the mixing chamber walls, the size of the recirculation bubble reduces, resulting in a lower jet spreading, similar to our case. We can reasonably conclude that the different Coanda surfaces modify the dynamics of the flow separation and recirculation, and thus the properties of the periodic symmetry breaking of the flow inside the mixing chamber.…”

Section: Flow Regimes Of the Modified Geometriessupporting

confidence: 87%

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: Flow Regimes Of the Modified Geometriessupporting

confidence: 87%

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

2021

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“…This confirms that each oscillator comprises two identical parts. From the time-averaged velocity field, it can be observed that the main jet in the mixing chamber shows no apparent movement, resulting in a jet flow very similar to a stationary jet (Wen et al , 2020). The figures also show that the fluid-jet power of the fluidic oscillator is greater than that of the SJ.…”

Section: Results and Interpretationsmentioning

confidence: 99%

Characterisation and comparison of unsteady actuators: a fluidic oscillator and a sweeping jet

Serrar¹,

Khlifi²,

Kourta

2021

HFF

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Purpose The purpose of this study is to compare two unsteady actuators: an oscillator and a sweeping jet. Both actuators can produce an oscillating jet of different amplitudes and frequencies without any moving parts, making them an attractive actuator concept. The Coanda effect phenomenon can explain the operating principles of these two unsteady actuators. Design/methodology/approach A numerical study was conducted to compare the amplitudes and frequencies of fluidic and sweeping jet (SJ) oscillators to obtain an efficient actuator to control separated flows at high Reynolds numbers. For this goal, two-dimensional unsteady Reynolds-averaged Navier-Stokes simulations were carried out using computational fluid dynamics (CFD) fluent code to evaluate the actuator performances. The discrete fast Fourier transform method determined the oscillation frequencies. Findings The oscillation frequencies gradually increase as the inlet pressure increases. The characteristics and dimensions of the vortices produced in the mixing chamber and feedback loops vary overtime when the injected fluid is swept sideways. The frequencies supplied by the SJ are stronger than those obtained by the fluidic oscillator, which may contribute to improving the aerodynamic performance at a lower power supply cost. Originality/value The existence of the splitter in the fluidic oscillator led to the production of separate pulses, which would be useful in various industrial applications, including active control of combustion and mixing processes while other applications such as flow separation control require SJs. With the latter actuator higher and interesting frequencies can be obtained, leading to efficient flow control.

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“…Below this high velocity zone, two localized regions with relatively higher velocities (orange) branch out in a direction parallel to each side of the exit nozzle. They are associated with the double peak velocity profile typically exhibited by a sweeping jet (Aram et al, 2018;Wen et al, 2018;Wen et al, 2020).…”

Section: Sweeping Jet At the Quiescent Flow Conditionmentioning

confidence: 93%

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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Flow dynamics of a fluidic oscillator with internal geometry variations

Cited by 32 publications

References 39 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

Characterisation and comparison of unsteady actuators: a fluidic oscillator and a sweeping jet

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

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