Aerodynamic investigation of an S-shaped intake employing sweeping jet actuators based on proper orthogonal decomposition

The central curvature change of the S-shaped intake exacerbates the three-dimensional flow separation, resulting in total pressure and swirl distortions at the outlet. In this paper, an efficient active flow control technique, the sweeping jet actuator, was applied to control flow separation. The instantaneous characteristics of the flow field inside and outside the actuator were revealed by using validated numerical simulation methods. In addition, the effect of the sweeping jet on the aerodynamic performance of the S-shaped intake was investigated. Proper orthogonal decomposition (POD), an analysis method used to extract the main feature components of data, was applied to decompose the flow field structure at the S-shaped intake outlet in this study. The results highlight the external flow field characteristics of the actuator, with a jet sweeping range of up to ±40° and a sweeping frequency of 1 500 Hz, corresponding to a Strouhal number of 0.018. When the jet momentum coefficient is only 0.116%, the total pressure loss coefficient and pressure distortion index are reduced by 5.6% and 24.76%, respectively. This study demonstrates the critical role of momentum injection and discretization in inhibiting flow separation in the channel. The POD-based analysis indicates that a sweeping jet with high momentum can significantly enhance the energy in the flow passage and reduce the vorticity intensity of the first three modes. The stable mode structures exist near the outlet, exhibiting excitation frequency and frequency-doubling properties. The findings of this research provide essential input conditions for subsequent distortion studies.