On the topology patterns and symmetry breaking in two planar synthetic jets
Eva Muñoz, Soledad Le Clainche
Abstract
This article studies the flow structures and main patterns driving the flow dynamics in one and two planar synthetic jets. We perform numerical simulations at different Reynolds numbers (Re), for a similar forcing frequency, to model the synthetic jet flow and the two planar synthetic jets, which present a movement in-phase (synchronous jets) and out-of-phase (asynchronous jets). We identify two types of flow regimes as function of the Reynolds number: (i) the flow is symmetric and (ii) the symmetry is broken at Re ≈110 and Re ≈140 for the single and the synchronous jets, respectively. On the contrary, the flow is always asymmetric in the two asynchronous jets. We calculate the thrust produced by the several jet configurations, finding that the thrust produced by a single jet is always half of the thrust produced by the two synchronous jets; however, this quantity is much smaller in the asynchronous jets. Finally, we use higher order dynamic mode decomposition to identify the main patterns driving the flow dynamics. The solution is periodic in the single and two synchronous jets, with the forcing frequency (St*) as the dominant mode. The emerging rise in amplitude of a low-frequency mode (St0 = St*/6) that sub-harmonic of the forcing frequency as the Reynolds number increases suggests a connection between this mode and the symmetry breaking. A new mode is identified in the asynchronous jets, breaking the flow periodicity.