Characteristics of array of distributed synthetic jets and effect on turbulent boundary layer

Lu, Lianshan; Li, Dong; Gao, Zhenghong; Cao, Zhen; Bai, Yu; Zheng, Junjian

doi:10.1007/s10409-020-01001-x

Cited by 14 publications

(5 citation statements)

References 34 publications

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“…In the further downstream direction, the effect gradually decreases as it keeps away from the synthetic jet control, which is similar to the result from Lu et al [35] In total, the synthetic jet has a drag reduction effect on the local flow field and the effect is not uniform.…”

Section: -7supporting

confidence: 85%

Effects of single synthetic jet on turbulent boundary layer

Zhang

Wang

et al. 2022

Chinese Phys. B

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The turbulent boundary layer (TBL) was actively controlled by the synthetic jet generated from a circular hole. According to datasets of velocity fields acquired by a time-resolved particle image velocimetry (TR-PIV) system, the average drag reduction rate of 6.2% was obtained downstream of the hole with control. The results of phase averaging show that the synthetic jet generates one vortex pair each period and the consequent vortex evolves into hairpin vortex in the environment with free-stream, while the reverse vortex decays rapidly. By statistical average, it can be found that a low-speed streak is generated downstream. Induced by the two vortex legs, the fluid under them converges to the middle. The drag reduction effect produced by the synthetic jet is local, and it reaches the maximum at x + = 400, where the drag reduction rate reaches about 12.2%. After extraction of coherent structure by the spatial two-point correlation analysis, it can be seen that the synthetic jet suppresses the streamwise scale and wall-normal scale of the large-scale coherent structure, and slightly weakens the spanwise motion to achieve the effect of drag reduction.

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Section: -7supporting

confidence: 85%

Effects of single synthetic jet on turbulent boundary layer

Zhang

Wang

et al. 2022

Chinese Phys. B

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“…The above properties of the synthetic jet signify that it can be implemented in drag reduction control in a TBL. [29] 024702-2…”

Section: Experimental Setup and Proceduresmentioning

confidence: 99%

“…This dual-peak phenomenon has been corroborated by previous studies. [29,33] Additionally, in the process of moving along the streamwise and the wall-normal direction, the spanwise vortex generated by the synthetic jet 024702-3 continuously interacts with the surrounding fluid resulting in a large turbulence intensity, and the peak in the Tu + profile can be considered as the center of the spanwise vortex. [29] After the peak, the synthetic jet gradually loses its influence on the flow field, and Tu + finally shows a similar trend to the uncontrolled case.…”

Section: Turbulence Statisticsmentioning

confidence: 99%

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Experimental investigation on drag reduction in a turbulent boundary layer with a submerged synthetic jet

Li¹,

Wang²,

Wang³

et al. 2022

Chinese Phys. B

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This work investigates the active control of a fully developed turbulent boundary layer by a submerged synthetic jet actuator. The impacts of the control are explored by measuring the streamwise velocities using particle image velocimetry, and reduction of the skin-friction drag is observed in a certain range downstream of the orifice. The coherent structure is defined and extracted using a spatial two-point correlation function, and it is found that the synthetic jet can efficiently reduce the streamwise scale of the coherent structure. Proper orthogonal decomposition analysis reveals that large-scale turbulent kinetic energy is significantly attenuated with the introduction of a synthetic jet. The conditional averaging results show that the induction effect of the prograde vortex on the low-speed fluid in a large-scale fluctuation velocity field is deadened, thereby suppressing the bursting process near the wall.

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“…The perturbation intensity of the synthetic jet attenuated along the streamwise direction, and the perturbation was mainly concentrated in the logarithmic region and extended to the outer region of TBL, which could obviously change the flow field structure of TBL. Lu et al (2020) used circular synthetic jet array to control the fully developed TBL. Their research exhibited that that the injection of synthetic jet effectively suppressed the bursting events intensity of turbulence in the near-wall region and the lifting effect of synthetic jet increased the normal height of streamwise vortex.…”

Section: Introductionmentioning

confidence: 99%

Effects of single circular synthetic jet on turbulent boundary layer

Zhang,

Li,

Ping

et al. 2023

J Hydrodyn

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The periodic synthetic jet emerging from a circular hole actively controls the turbulent boundary layer (TBL). A time-resolved particle image velocimetry (TR-PIV) system was designed to capture the velocity field database and based on the single-pixel ensemble correlation (SPEC) algorithm, an average drag reduction rate of 6.2% was obtained. The results show that the synthetic jet causes a wide range of low momentum zones and a low-speed streak in the downstream flow field. And the places where the disturbance intensity is strong are often accompanied by a larger velocity deficit. The instantaneous flow fields are visualized with the Finite-Time Lyapunov Exponent (FTLE), and the hairpin vortex packet composed of five hairpin vortices and the generation of new hairpin vortices are observed when there is no control. Under the action of the synthetic jet, the hairpin vortices are continuously generated from the jet hole. The synthetic jet mainly achieves the drag reduction effect mainly by modulating the mean convection term 𝑐 𝐶 and the spatial development term 𝑐 𝐷 . The drag reduction effect appears in the region of 𝑥/𝛿 0 > 0.38, and the maximum drag reduction rate is 12.2% at 𝑥/𝛿 0 = 0.5,, and then gradually decreased. Using proper orthogonal decomposition (POD), it is found that the synthetic jet reduces the energy proportion of the large-scale energetic structures. After the conditional average, the synthetic jet limits the influence range of bursting events at various scales in the near-wall region, and weakens the normal transport of momentum and energy brought about by large-scale ejection events (Q2 events) and the wall friction resistance caused by large-scale sweep events (Q4 events).

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Characteristics of array of distributed synthetic jets and effect on turbulent boundary layer

Cited by 14 publications

References 34 publications

Effects of single synthetic jet on turbulent boundary layer

Effects of single synthetic jet on turbulent boundary layer

Experimental investigation on drag reduction in a turbulent boundary layer with a submerged synthetic jet

Effects of single circular synthetic jet on turbulent boundary layer

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