Interacting synthetic jets: fundamentals and applications

Abstract

Synthetic jets are zero-net-mass-flux devices that create a train of vortical structures from alternating blowing and suction cycles through an orifice. In this thesis the interaction of synthetic jets with three different flows is investigated: neighbouring synthetic jets interacting with each other, a synthetic jet interacting with the separated flow over a backward-facing step and the interaction of a synthetic jet with a turbulent boundary layer. In general, for these different flows, it is proposed that the vortical structures of the jet are the leading driver behind observed interactions. This supplements the
literature where interactions are often explained based on the low pressure behind jet pulses, viscous blockage of jet pulses or frequency modes amplified by the jet frequency. Using the physical mechanisms presented in this thesis, a higher level of control over interacting synthetic jets can be obtained. This includes control over the direction of two parallel synthetic jets, control over the reattachment length of the separated flow behind a backward-facing step and control over the trajectory and the wake of a synthetic jet issuing into a turbulent boundary layer. The focus in the present thesis is on the physical mechanisms behind observed interactions rather than on optimal control. The underlying idea is that the obtained physical understanding can be used in subsequent studies to develop optimal control.

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Identifiers

ORCID for Bharathram Ganapathisubramani: orcid.org/0000-0001-9817-0486

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