Jet Oscillation Frequency Characterization of a Sweeping Jet Actuator

Oz, Furkan; Kara, Kursat

doi:10.3390/fluids5020072

Cited by 18 publications

(8 citation statements)

References 48 publications

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“…We can also estimate the Strouhal number of the actuator as St = f 0 h∕U in . The Strouhal number of the reference geometry is in the range of 0.013 < St < 0.016 , which corresponds well to the values in literature (Woszidlo et al 2019;Slupski et al 2019;Oz and Kara 2020).…”

Section: The Reference Actuatorsupporting

confidence: 85%

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: The Reference Actuatorsupporting

confidence: 85%

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

2021

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“…The baseline geometry considered for the present study was a curved SWJA having two feedback channels, a mixing chamber, and an exit nozzle [5][6][7][8]. The baseline CAD geometry can be shared upon request.…”

Section: Numerical Setup and Geometric Detailsmentioning

confidence: 99%

“…Similarly, N-40, N-50, and N-80 have element sizes of h/40, h/50, and h/80, respectively. For a gradual increment of the element size, two spheres of influence were used having radii of 7.5 h and 20 h with a growth rate of 1.15 [6,7]. The mesh name was based on the element size chosen for the smaller sphere, but for the entire structure, the element size was controlled by keeping a tenth of the characteristic length (N-10) (Figure 3), except for N-80, which was considered to be exact, so we used an element size of N-40 for the entire flow domain.…”

Section: Mesh Independence Testmentioning

confidence: 99%

“…The computational analysis was validated with several experimental and numerically proven data by varying the geometry, type and the working fluid accordingly. A computational study for the characterization of the jet oscillation of the actuator was conducted by Furkan et al [7] by varying the mass flow rate from incompressible to subsonic compressible flow. This 3D URANS model with a stable mesh structure was proven to be a cost-effective alternative for SWJA performance analysis.…”

Section: Introductionmentioning

confidence: 99%

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The Influence of Exit Nozzle Geometry on Sweeping Jet Actuator Performance

Alam

Kara

2022

Fluids

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When pressurized with a fluid, the sweeping jet actuator (SWJA) emits a self-induced and self-sustained temporally continuous, but spatially oscillating bi-stable jet at the outlet. The SWJA adds up local momentum using the Coanda extension without any moving parts and, therefore, can be a promising tool for suppressing aerodynamic flow separation. However, the SWJA needs to be integrated into curved aerodynamic surfaces with an angle. The present study focuses on investigating the effects of various exit nozzle geometries on the flow field. The geometric parameters considered were the exit nozzle angle, diffuser arm length, and curvature. The working fluid was air, and the mass flow rate was 0.015 lb/s. A set of time-dependent flow fields was computed using a two-dimensional unsteady Reynolds-averaged Navier–Stokes (URANS) simulation. The time history of pressure was recorded inside the upper and lower feedback channels. The jet oscillation frequency was obtained by employing the fast Fourier transform (FFT) for all datasets. The results were compared against the baseline case and data available in the literature. The results showed that external geometric variations at the nozzle exit had a negligible impact on the oscillation frequency. However, there were notable effects on the pressure and velocity distribution in the flow field, indicating that the actuator had sensitivity towards the geometric variation of the exit nozzle—the wider the exit nozzle, the lower the downstream velocity. Notably, we observed that the mean velocity at the exit nozzle downstream for the curvature case was 40.3% higher than the reference SWJA.

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“…This made it possible to speed up the jet by a convergent-divergent nozzle at the output of the oscillator. Oz and Kara (2020) investigated numerically a SJ to investigate jet oscillation frequency. The unsteady Reynolds-averaged Navier-Stokes (URANS) model provided a computationally less expensive but still accurate alternative for researchers to investigate the properties of jet oscillations.…”

Section: Introductionmentioning

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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Jet Oscillation Frequency Characterization of a Sweeping Jet Actuator

Cited by 18 publications

References 48 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

The Influence of Exit Nozzle Geometry on Sweeping Jet Actuator Performance

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

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