Experimental study on spectrum and multi-scale nature of wall pressure and velocity in turbulent boundary layer

Zheng, Xing; Jiang, Nan

doi:10.1088/1674-1056/24/6/064702

Cited by 11 publications

(9 citation statements)

References 55 publications

(82 reference statements)

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“…We obtained time sequences of the streamwise velocity signal at 74 different wall-normal locations. Each sequence comprised 2 22 velocity samples or approximately 42 s [33].…”

Section: Experimental Setup and Parametersmentioning

confidence: 99%

Active control of multiscale features in wall-bounded turbulence

et al. 2019

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This study experimentally investigates the impact of a single piezoelectric (PZT) actuator on a turbulent boundary layer from a statistical viewpoint. The working conditions of the actuator include a range of frequencies and amplitudes. The streamwise velocity signals in the turbulent boundary layer flow are measured downstream of the actuator using a hot-wire anemometer. The mean velocity profiles and other basic parameters are reported. Spectra results obtained by discrete wavelet decomposition indicate that the PZT vibration primarily influences the near-wall region. The turbulent intensities at different scales suggest that the actuator redistributes the near-wall turbulent energy. The skewness and flatness distributions show that the actuator effectively alters the sweep events and reduces intermittency at smaller scales. Moreover, under the impact of the PZT actuator, the symmetry of vibration scales' velocity signals is promoted and the structural composition appears in an orderly manner. Probability distribution function results indicate that perturbation causes the fluctuations in vibration scales and smaller scales with high intensity and low intermittency. Based on the flatness factor, the bursting process is also detected. The vibrations reduce the relative intensities of the burst events, indicating that the streamwise vortices in the buffer layer experience direct interference due to the PZT control.

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“…We obtained time sequences of the streamwise velocity signal at 74 different wall-normal locations. Each sequence comprised 2 22 velocity samples or approximately 42 s [33].…”

Section: Experimental Setup and Parametersmentioning

confidence: 99%

Active control of multiscale features in wall-bounded turbulence

et al. 2019

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“…An active control scheme with double piezoelectric vibrators was employed in the present experiments. On the basis of the research with a single piezoelectric vibrator, [27][28][29] interference and regulation of multi-scale coherent structure bursts in a turbulent boundary layer were achieved by synchronous and asynchronous vibration of double piezoelectric vibrators respectively, which were embedded on the wall along the span-wise direction, and thus the drag reduction was achieved through different amplitudes and frequencies on the piezoelectric vibrators.…”

Section: Introductionmentioning

confidence: 99%

Active control of wall-bounded turbulence for drag reduction with piezoelectric oscillators

Jianxia¹,

Jiang²,

Zheng³

et al. 2018

Chinese Phys. B

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An experimental investigation was performed for active control of coherent structure bursting in the near-wall region of the turbulent boundary layer. By means of synchronous and asynchronous vibrations with double piezoelectric vibrators, the influence of periodic vibration of the double piezoelectric vibrators on the mean velocity profile, drag reduction rate, and coherent structure bursting is analyzed at Re θ = 2766. The case with 100 V/160 Hz-ASYN is superior to other conditions in the experiment and a relative drag reduction rate of 18.54% is exciting. Asynchronous vibration is more effective than synchronous vibration in drag reduction at the same voltage and frequency. In all controlled cases, coherent structures at large scales are regulated while the small-scale structures are stimulated. The fluctuating velocity increases significantly. A periodic regulating effect on the coherent structure can be seen in the ASYN control conditions at the frequency of 160 Hz.

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“…The sampling rate and low pass cut-off frequency were 100 and 50 kHz, respectively. Each sequence comprised of 2 22 velocity samples or approximately 42 s. [31] 3. Results and discussion…”

Section: Experimental Setup and Conditionsmentioning

confidence: 99%

Effect of high- or low-speed fluctuations on the small-scale bursting events in an active control experiment*

Cui¹,

Jiang²,

Tang³

2021

Chinese Phys. B

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Active control of a fully developed turbulence boundary layer (TBL) over a flat plate has been investigated with a statistical view. The piezoelectric (PZT) oscillator is employed to produce periodic input into the inner region of the TBL. A wall probe is fixed upstream of the oscillator to identify the high- or low-speed fluctuations as the detecting signals. Then, the impact of the detecting signals on the small-scale bursting process is investigated based on the data acquired by the traversing probe downstream of the oscillator. The results indicate that the small-scale bursting intensity is restrained more apparently at high-speed detecting fluctuations but less impacted at low-speed detecting fluctuations. Furthermore, the perturbed-scale fluctuations arrange the small-scale bursting process in the near-wall region. The detecting signals have an obvious impact on this arrangement, especially the high-intensity regions of the small-scale bursting events: the vibration enhances the intensity at high-speed detecting signals but weakens it at low-speed detecting signals in these regions, which gives a direct evidence on how detecting signals interfering the small-scale bursting process.

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Experimental study on spectrum and multi-scale nature of wall pressure and velocity in turbulent boundary layer

Cited by 11 publications

References 55 publications

Active control of multiscale features in wall-bounded turbulence

Active control of multiscale features in wall-bounded turbulence

Active control of wall-bounded turbulence for drag reduction with piezoelectric oscillators

Effect of high- or low-speed fluctuations on the small-scale bursting events in an active control experiment*

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