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Mechanism of flow separation control by coherent vortices induced by synthetic jet
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DOI：10.1017/jfm.2026.11754.png)
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Abstract
En 中文
This study employs synthetic jet actuation (SJA) to control large-scale flow separation on the suction side of a NACA0015 aerofoil at a Reynolds number of 2.1 . The underlying control mechanism is investigated using large-eddy simulations to resolve the dynamics of jet-induced coherent structures associated with the low-frequency actuation. During the periodic blowing and suction cycle; two distinct types of spanwise coherent vortices are identified: blowing-induced vortices (BIVs) and suction-induced vortices (SIVs); which differ significantly in spatial distribution and energy content. As these vortices are convected downstream at speeds comparable to the free-stream velocity; BIVs exhibit a significantly slower rate of energy decay; whereas SIVs dissipate rapidly; particularly near the trailing edge. Triple decomposition analysis shows that energy addition is primarily associated with the coherent velocity components. Notably; BIVs exhibit a stronger entrainment capacity; enhancing momentum exchange between the separated shear layer and outer flow via coherent Reynolds shear stresses. This intensified exchange facilitates the outward transport of low-momentum fluid; effectively enhancing aerodynamic performance and delaying flow separation. Furthermore; spectral proper orthogonal decomposition reveals distinct energy peaks centred at the actuation frequency and its harmonics. Among the two vortex types; BIVs contribute most of the coherent spectral energy; highlighting their critical role in the overall effectiveness of the flow control. These findings elucidate the flow organisation and modulation mechanisms associated with low-frequency SJA under deep-stall conditions; and provide a physical interpretation of the observed reorganisation of the separated flow.
Keywords:
vortex dynamics
flow control
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