Flow characteristics of a wall-attaching oscillating jet over single-wall and double-wall geometries

Mohammadshahi, Shabnam; Samsam-Khayani, Hadi; Nematollahi, Omid; Kim, Kyung Chun

doi:10.1016/j.expthermflusci.2019.110009

Cited by 19 publications

(14 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although a sweeping jet pattern was produced and controlled by the internal part (double-feedback fluidic oscillator), the jet did not oscillate at this range of Reynolds number as it did for the sweeping jet in the free external domain. This phenomenon was opposite to the results of the previous study, while the external domain had steps in the normal direction to the emitted flow [31], where notable differences between the effect of confinement and Re number could be concluded.…”

Section: Velocity Distributioncontrasting

confidence: 99%

See 1 more Smart Citation

Experimental Study on Physical Behavior of Fluidic Oscillator in a Confined Cavity with Sudden Expansion

2020

Self Cite

View full text Add to dashboard Cite

In this study, two-dimensional time-resolved particle image velocimetry (2D-TR-PIV) was used to investigate the effect of the external domain on oscillating jets from double-feedback fluidic oscillators. Two different cases with different Re numbers (2680–10,730), as free external domain and fully confined were studied. Time-averaged results showed although a self-oscillating jet was attained for the free external domain, it could not be achieved for a fully confined geometry. For a fully confined geometry at Re = 2680, two symmetric vortices did not allow the jet to oscillate and at Re = 6440, the flow pattern in the external region became non-symmetric due to the Coanda vortex, subsequently, the self-oscillating jet was not observed. At Re = 10,730, the strength of the jet was inclined to cope with such vortices and tended to oscillate. However, strong vortices were created near the exit region of the fluidic oscillator, which led to an almost non-symmetric pattern. In addition, the proper orthogonal decomposition (POD) method and phase-averaged analysis were applied to obtain the unsteady behavior of flow and the most energetic dynamic structure. Interestingly, at Re = 6440, the third mode was still energetic for fully confined, but for other cases, the first two modes were the most energetic modes, which showed vigorous coherent structures.

show abstract

Section: Velocity Distributioncontrasting

confidence: 99%

“…They concluded that by increasing the mass supply for the fixed geometry, the frequency increases. In numerous studies, researchers focused on the external domain of the fluidic oscillator and discussed the impact of the oscillating jet, relative to the spreading angle, which is controlled by the jet flow rate [30][31][32][33][34][35].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Physical Behavior of Fluidic Oscillator in a Confined Cavity with Sudden Expansion

2020

Self Cite

View full text Add to dashboard Cite

show abstract

“…Mohammadshahi et al [20] studied the flow structures outside an oscillator by PIV measurement. They also numerically studied the effect of external domain on the oscillation frequency and maximum spreading angle, and there was no significant effect on the frequency.…”

Section: Flow Features Of Feedback Fluidic Oscillatorsmentioning

confidence: 99%

Flow features of a new fluidic oscillator using time-resolved PIV measurement and 3D numerical simulation

et al. 2021

Self Cite

View full text Add to dashboard Cite

The current study measures the instantaneous velocity field inside and outside a new designed fluidic oscillator using planar time-resolved PIV technique on its symmetry plane in a water tank. The instantaneous velocity field showed that the interaction of four vortices with the jet was the main reason of jet oscillation inside the main chamber. Threedimensional transient numerical solutions were also carried out using Ansys-Fluent 2020R2 software. Four turbulence models (k-ε, k-ε RNG, k-ω, and k-ω SST) were used for these numerical solutions, which their results were then compared with the PIV results, qualitatively and quantitatively. The comparison showed that the k-ε and k-ω SST models were better for simulating the flow of the new oscillator. However, both models over-predicted the jet spreading angle and oscillation frequency compared to the PIV results. A similar PIV measurement was accomplished outside the conventional oscillator to compare the timeaveraged velocity fields of the new and conventional oscillators. The comparison showed that the amplitude and frequency of the new oscillator were, respectively, lower and higher than those of the conventional one. The time-averaged velocity and momentum flux outside the new oscillator was significantly higher than for the conventional one. Abbreviations A Throat area (m 2 ) D Throat height (m) D h Hydraulic diameter (m) Fr Oscillation frequency (1/s) f Oscillation frequency (1/s) H Domain height outside the oscillator (m) rate k Turbulence kinetic energy (m 2 /s 2

show abstract

“…They showed that the inlet pressure needed to be about 20% lower to create a uniform discharge. Mohammadshahi et al (2020) experimentally studied the flow pattern outside a fluidic oscillator and investigated the effect of the external domain on the oscillation frequency and maximum deflection angle. They concluded that the external domain does not have a significant effect on the frequency.…”

Section: Performance Parameters Of the Original Oscillatormentioning

confidence: 99%

Design of a novel vortex-based feedback fluidic oscillator with numerical evaluation

Nili-Ahmadabadi

Cho

Kim

2020

Engineering Applications of Computational Fluid Mechanics

Self Cite

View full text Add to dashboard Cite

In this study, a new vortex-based fluidic oscillator was designed whose performance was numerically evaluated by solving the URANS equations. The oscillator consists of a primary chamber and secondary chamber, separated by a mid-throat and connected by two feedback channels. The jet passing through these chambers forms two pairs of vortices inside the primary and secondary chambers. These vortices roll onto the jet shear layer, and gradually disturbs the jet symmetry. As a result, the vortices grow and shrink asymmetrically, activating the feedback flow to make a harmonic oscillation. The collision of the oscillating jet with the mid-throat traps a part of the jet shear layer in the primary chamber, which forms a strong vortex, returning the jet toward the other side of the midthroat. The vortex inside the secondary chamber causes the jet to attach to one side of the secondary chamber, deviating the outlet jet to the other side. To compare the performance of the new oscillator with the original one, URANS equations were solved for two-dimensional models of both oscillators with the same grid generation and boundary conditions. The new oscillator had a higher oscillation frequency, a lower pressure drop, and a higher output momentum flux.

show abstract

Flow characteristics of a wall-attaching oscillating jet over single-wall and double-wall geometries

Cited by 19 publications

References 24 publications

Experimental Study on Physical Behavior of Fluidic Oscillator in a Confined Cavity with Sudden Expansion

Experimental Study on Physical Behavior of Fluidic Oscillator in a Confined Cavity with Sudden Expansion

Flow features of a new fluidic oscillator using time-resolved PIV measurement and 3D numerical simulation

Design of a novel vortex-based feedback fluidic oscillator with numerical evaluation

Contact Info

Product

Resources

About