Characteristics of array of distributed synthetic jets and effect on turbulent boundary layer
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RESEARCH PAPER
Characteristics of array of distributed synthetic jets and effect on turbulent boundary layer Lianshan Lu1 · Dong Li1 · Zhenghong Gao1 · Zhen Cao1 · Yu Bai1 · Jie Zheng1 Received: 22 June 2020 / Revised: 23 July 2020 / Accepted: 13 August 2020 © The Chinese Society of Theoretical and Applied Mechanics and Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract An array of distributed round synthetic jets was used to control a fully developed turbulent boundary layer. The study focused on the related skin friction drag reduction and mechanisms involved. The control effects were analyzed by measuring the streamwise velocities using a hot-wire anemometer downstream of the array. A reduction in the skin friction was observed both in the regions downstream of the orifices and in the regions between two adjacent orifices. A statistical analysis with the variable-interval time-averaging (VITA) technique demonstrated a weakened bursting intensity with synthetic jet in the near-wall region. The streamwise vortices were lifted by the upwash effect caused by synthetic jet and induced less low-speed streaks. The control mechanism acted in a way to suppress the dynamic interaction between the streamwise vortices and low-speed streaks and to attenuate the turbulence production in the near-wall region. The forcing frequency was found to be a more relevant parameter when synthetic jet was applied in turbulent boundary layer flow control. A higher forcing frequency induced a higher reduction in the skin friction. The power spectral density and autocorrelation of the fluctuating velocities showed that the synthetic jets gradually decayed in the streamwise direction, having an effect as far as 34.5 times the displacement thickness that was on the trailing edge of the distributed synthetic jets array. Keywords Distributed synthetic jets · Flow control · Turbulent boundary layer · Skin friction drag reduction · Hot-wire
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1 Introduction As is well known, viscous drag, which is mainly related to the skin friction drag caused by the interaction of the boundary layer flow with the aircraft surface, represents approximately 50% of the total drag under flight conditions. This results in huge fuel consumption and environmental pollution. It is believed that even a 1% skin friction drag reduction will produce significant improvements of the efficiency of air transportation. In general, the skin friction drag of turbulent boundary layer flow is ten times that of laminar boundary layer flow, and the turbulent boundary layer flow always occupies a large proportion of the aircraft surface during the flight. For this reason, people have been dedicated to the pursuit of skin friction drag reduction in turbulent boundary layers for decades, and many passive and active flow control strategies have been proposed. Cui et al. [1] conducted
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Dong Li [email protected] School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China
active control of turbulent bounda
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