Characterization of Dual Two-Dimensional Synthetic Jets in Cross Flow at Low Mach Number

Abstract

This paper explores the interaction between dual synthetic jets with identical geometries via studies of in-phase oscillations with different jet proximities, and fixed jet proximity with out- of-phase oscillations. The two-dimensional synthetic jet plenums were 10mm wide and 39.2mm deep with an orifice 1.0mm wide and 0.9659mm deep and run at a frequency of 1632.65Hz creating a maximum average outflow velocity of 165.63m/s and a maximum average inflow velocity of 99.48m/s. A single cross-flow Mach number of 0.4 and Reynolds number based on momentum thickness at the first jet of 3127 was employed for all the calculations. Jet proximity ranged from 12 to 44mm for the in-phase jets, while phase shifts of 0 to 315 degrees were explored for a 16mm proximity jet. Jet performance is judged via the momentum coefficient and results explained through the use of vorticity and pressure contour time histories. Results demonstrate that the close proximity jets (below 26mm) suffer relative to isolated jets because of the adverse interaction of pressure waves and vortex shedding, whereas the high proximity jets (above 26mm) experienced favorable interactions. The physics of these flows demonstrate that upstream traveling pressure waves from the second jet have the greatest effect on the first jet, while a combination of downstream traveling pressure waves and a shed vortex contribute to the behavior of the second jet. Results for the phase-shifted 16mm proximity jets demonstrated similar flow physics and momentum coefficient behavior. A phase shift of 180-degrees produced the highest momentum coefficient and locally favorable pressure and vorticity physics. The results suggest the possibility of tuning a dual synthetic jet system for optimal performance.