Flapping dynamics of inverted flags in a side-by-side arrangement

Two side-by-side inverted flags in a uniform flow were simulated using the immersed boundary method. An energy harvesting system consisting of the two inverted flags was analyzed, and the flapping motions of the flags were investigated with consideration for the flow-mediated interactions between them. The flapping motions of the flags were determined from the spanwise gap distance between the trailing edges of the two flags. In-phase and out-of-phase flapping motions were observed by varying the gap distance and the initial configuration. The relative spanwise displacement of the leading edge from the trailing edge, the strain energy, and the flapping frequency was examined as a function of the gap distance and the bending rigidity. The large peak-to-peak amplitude was induced by placing an additional inverted flag. The large mean strain energy was achieved due to the intensified flapping motions of each flag. The vortical structures produced by the inverted flags, along with the pressure and velocity distributions along the center line were explored for different gap distances.