Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator

Sarwar, Wasim; Bergadà, Josep M.; Mellibovsky, Fernando

doi:10.1016/j.apm.2021.01.044

Cited by 7 publications

(8 citation statements)

References 27 publications

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“…Once the jet enters the FO, initially, the jet travels a straight path inside the FO chamber (Figure 6 —first row). Once the jet has entered a critical length inside the chamber, the Kelvin–Helmholtz instability 58 sets in, and the oscillations start at the end of the jet. These small‐scale instabilities are oscillatory in nature which facilitates the Coandă effect.…”

Section: Resultsmentioning

confidence: 99%

Flow physics of planar bistable fluidic oscillator with backflow limbs

Madane

Khalde²,

Pandit

et al. 2022

AIChE Journal

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Fluidic oscillators (FOs) are used in a variety of applications, including process control and process intensification. Despite the simple design and operation of FOs, the fluid dynamics of FOs exhibit rich complexities. The inherently unstable flow, jet oscillations, and resulting vortices influence mixing and other transport processes. In this work, we computationally investigated the fluid dynamics of a new design of a planar FO with backflow limbs. The design comprised of two symmetric backflow limbs leading to bistable flow. The unsteady flow dynamics, internal recirculation, jet oscillations, secondary flow vortices were computationally studied over a range of inlet Reynolds numbers (2400-12,000). The nature and frequency of the jet oscillations were quantified. The computed jet oscillation frequency was compared with the experimentally measured (using imaging techniques) jet oscillation frequency. The flow model was then used to quantitatively understand mixing, heat transfer, and residence time distribution. The approach and the results presented in this work will provide a basis for designing FO's with desired flow and transport characteristics for various engineering applications.

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Section: Resultsmentioning

confidence: 99%

Flow physics of planar bistable fluidic oscillator with backflow limbs

Madane

Khalde²,

Pandit

et al. 2022

AIChE Journal

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“…For all cases studied, a large reverse flow at the FC has been observed (see Figures 7b, 12b and 16b). In fact, this large reverse flow was not previously observed in the FO configurations studied by [14,[25][26][27] or even by [28], where the same FO configuration was studied but at a very low Reynolds number. In the present subsection, an oscillation cycle is carefully analyzed, linking the velocity and pressure fields at different instants with the forces acting over the jet; the concept here is to unveil the forces acting on the jet as it enters the mixing chamber and understand why the jet keeps oscillating, even when this large reverse flow exists.…”

Section: Discussion Of the Results Origin Of The Self-sustained Oscil...mentioning

confidence: 59%

“…Bergada et al [27] studied the effect of feedback channel (FC) length on FO performance for compressible flow conditions; they found that at large feedback channel lengths, the former main oscillation tends to disappear, the jet inside the mixing chamber simply fluctuates at high frequencies, and as the feedback channel (FC) length exceeds a certain threshold the FO stops oscillating. In Sarvar et al [28], a novel shape of a fluidic oscillator (FO) in the laminar regime at a very low Reynolds number was studied; they observed that the jet sweeping angle amplitude is more pronounced for a two-dimensional FO as compared to a three-dimensional one at a fixed given Reynolds number, and the instability of the output jet becomes slightly chaotic at very low Reynolds numbers. In recent years, many researchers have been working on the analysis, design, and applications of FOs.…”

Section: Introductionmentioning

confidence: 99%

“…In this study, a newly designed fluidic oscillator (FO), previously studied by [28] at very low Reynolds numbers is analyzed using numerical methods at relatively high Reynolds numbers, and flow is assumed to be incompressible. Following the establishment of a typical linear correlation between the Reynolds number and the oscillating frequency of the outlet flow, the study addresses the impact of dimensional modifications in outlet width and mixing chamber wedge inclination angle.…”

Section: Introductionmentioning

confidence: 99%

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Analysis of a Novel Fluidic Oscillator under Several Dimensional Modifications

Karimzadegan,

Mirzaei,

Bergada

2024

Applied Sciences

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To activate the boundary layer in Active Flow Control (AFC) applications, the use of pulsating flow has notable energy advantages over constant blowing/suction jet injections. For a given AFC application, five parameters, jet location and width, inclination angle, frequency of injection, and the momentum coefficient, need to be tuned. Presently, two main devices are capable of injecting pulsating flow with a momentum coefficient sufficient to delay the boundary layer separation: these are zero-net-mass-flow Actuators (ZNMFAs) and fluidic oscillators (FOs). In the present study, a novel FO configuration is analyzed for the first time at relatively high Reynolds numbers, and fluid is considered to be incompressible. After obtaining the typical linear correlation between the incoming Reynolds number and the outlet flow oscillating frequency, the effects of dimensional modifications on outlet width and mixing chamber wedge inclination angle are addressed. Modifications of the outlet width were observed to create large variations in FO performance. The origin of self-sustained oscillations is also analyzed in the present manuscript and greatly helps in clarifying the forces acting on the jet inside the mixing chamber. In fact, we can conclude by saying that the current FO configuration is pressure-driven, although the mass flow forces appear to be much more relevant than in previously studied FO configurations.

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“…Studies of the flutter-instability of a flag in incompressible inviscid fluid revealed several scenarios of transition [2]: quasi-periodic bifurcation was the underlying physical mechanism from periodic state to chaotic state, and a period-doubling bifurcation caused a transition from a symmetric periodic state to an asymmetric periodic state. Apart from these former typical scenarios, other intermediate bifurcations may also exist along the bifurcation route [10].…”

Section: Introductionmentioning

confidence: 99%

Transition to Periodic Behaviour of Flow Past a Circular Cylinder under the Action of Fluidic Actuation in the Transitional Regime

et al. 2021

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This study focuses on the numerical investigation of the underlying mechanism of transition from chaotic to periodic dynamics of circular cylinder wake under the action of time-dependent fluidic actuation at the Reynolds number = 2000. The forcing is realized by blowing and suction from the slits located at ±90∘ on the top and bottom surfaces of the cylinder. The inverse period-doubling cascade is the underlying physical mechanism underpinning the wake transition from mild chaos to perfectly periodic dynamics in the spanwise-independent, time-dependent forcing at twice the natural vortex-shedding frequency.

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Onset of temporal dynamics within a low reynolds-number laminar fluidic oscillator

Cited by 7 publications

References 27 publications

Flow physics of planar bistable fluidic oscillator with backflow limbs

Flow physics of planar bistable fluidic oscillator with backflow limbs

Analysis of a Novel Fluidic Oscillator under Several Dimensional Modifications

Transition to Periodic Behaviour of Flow Past a Circular Cylinder under the Action of Fluidic Actuation in the Transitional Regime

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