SYNTHETIC JETS

  • Glezer A
  • Amitay M
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Abstract

s Abstract The evolution of a synthetic (zero-net mass flux) jet and the flow mech-anisms of its interaction with a cross flow are reviewed. An isolated synthetic jet is produced by the interactions of a train of vortices that are typically formed by alternating momentary ejection and suction of fluid across an orifice such that the net mass flux is zero. A unique feature of these jets is that they are formed entirely from the working fluid of the flow system in which they are deployed and, thus, can transfer linear momentum to the flow system without net mass injection across the flow boundary. Synthetic jets can be produced over a broad range of length and timescale, and their unique attributes make them attractive fluidic actuators for a number of flow control applications. The interaction of synthetic jets with an external cross flow over the surface in which they are mounted can displace the local streamlines and induce an apparent or virtual change in the shape of the surface, thereby effecting flow changes on length scales that are one to two orders of magnitude larger than the characteristic scale of the jets. This control approach emphasizes an actuation frequency that is high enough so that the interaction domain between the actuator and the cross flow is virtually invariant on the global timescale of the flow, and therefore, global effects such as changes in aerodynamic forces are effectively decoupled from the operating frequency of the actuators. 1. OVERVIEW Jet-like flows having complex spatial and temporal characteristics can be engen-dered in a quiescent medium (or in a cross flow) by the advection and interactions of trains of discrete vortical structures (e.g., Saffman 1981). The hydrodynamic impulse that is necessary to form each of these vortices is imparted at the flow boundary by the momentary discharge of slugs of fluid through an orifice. The flow typically separates at the edge of the orifice, and a vortex sheet is formed and rolls into an isolated vortex that is subsequently advected away under its own self-induced velocity. Depending on the flow symmetry and the repetition rate, the dynamics and interactions of the vortical structures within a pulsed jet can lead to 0066-4189/02/0115-0503$14.00

Author-supplied keywords

  • aerodynamic forces
  • boundary-layer separation
  • jet cross-flow interaction
  • synthetic jets
  • turbulence
  • vortices

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Authors

  • Ari Glezer

  • Michael Amitay

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