Large-Eddy simulations of circular synthetic jets in quiescent surroundings and in turbulent cross-flow

Large-Eddy simulation (LES) is used to investigate the physical processes involved in the injection of a synthetic (zero-net-mass-flux) jet in quiescent surroundings and into a zero-pressure-gradient, turbulent boundary layer over a flat plate at conditions corresponding to experimental data obtained by others. The former case is studied because it constitutes a key ingredient of the latter. Specifically, it allows the computational framework to be verified, basic properties of synthetic jets to be studied, and the sensitivity of the jet structure to the details of the computational representation of the jet orifice to be investigated. In particular, the validity of representing the circular orifice, within a multi-block H-topology mesh, alternatively, by an equivalent square orifice, or by means of a solid-cell-blocking technique or via local mesh distortion, is examined. The boundary layer ahead of the jet is generated by a separate precursor simulation at a momentum-thickness Reynolds number Reθ=2380, providing the main simulation with a full and accurate description of the unsteady conditions at the computational inflow boundary. Time- and phase-averaged results are presented and compared against experimental data.