Modal analysis of dual syntehtic jets based on POD method

In order to understand the flow field characteristics of dual synthetic jets more deeply, particle image velocimetry (PIV) experiments were conducted. The temporal and spatial evolution of vortex structures in one cycle were analyzed. Proper orthogonal decomposition (POD) method was adopted. Flow structures, time coefficients, and power spectra of the first four modes were analyzed in detail. It was found that two cavities of the actuator were mutually compressed to form two strands of synthetic jet with a phase difference of 180°. Thus the energy efficiency and working frequency were doubly increased. The first four POD modes occupied 80.5% of the energy, and the frequencies of corresponding time coefficients were the working frequency and its second-order harmonic frequency, respectively. The first two POD transverse modes were symmetrically distributed and the third and fourth modes were anti-symmetrically distributed, while for the streamwise modes, the facts were just the opposite. This reflect the symmetrical characteristics of the dual synthetic jets' flow fields.