Three-dimensional interaction of a finite-span synthetic jet in a crossflow

Abstract

The formation and evolution of flow structures due to the interaction of a finite-span synthetic jet with a zero-pressure gradient laminar boundary layer were experimentally investigated using stereoscopic particle image velocimetry. A synthetic jet with three orifice aspect ratios of AR = 6, 12, and 18 was issued into a free-stream velocity of U∞ = 10 m/s (Reδ = 2000) at blowing ratios of Cb = 0.5–1.5. The interaction was found to be associated with two sets of flow structures: (1) a recirculation region downstream of the orifice due to virtual blockage, and (2) a steady streamwise vortex pair farther downstream. These two flow structures were characterized in detail. Tube-like velocity deficits in the free-stream were evident, as well as regions of increased velocity within the boundary layer. Reducing the aspect ratio of the orifice decreased the spacing of the edgewise vortices (generated due to the finite span of the orifice) as well as reducing the virtual blockage of the jet. A control volume analysis of the fluid streamwise momentum indicates that there is a momentum deficit just downstream of the jet orifice and the change in streamwise momentum is proportionally similar for all cases.

The interactions of rectangular synthetic jets with a laminar cross-flow

“…Ravi, Mittal & Najjar (2004) focused on interactions of square, and AR = 2 and 4 rectangular synthetic jets with a cross-flow using 3-D numerical simulations; however, the details on the evolution of vortical structures cannot be obtained from the limited results. Van Buren et al (2016 a ) used stereoscopic PIV to study AR = 6, 12 and 18 rectangular synthetic jets normally issued into a laminar boundary layer at VR = 0.5, 1 and 1.5. The flow fields were characterized by a recirculation region downstream of the orifice and a steady streamwise vortex pair farther downstream, akin to the findings in Smith (2002).…”

Vortex ring bifurcation and secondary structures in a finite-span synthetic jet

“…Van Buren et al. (2016) and Lindstrom, Monastero & Amitay (2018) in SPIV experiments and Belanger, Zingg & Lavoie (2020) in a large-eddy simulation reported potential bifurcations of the vortex rings from moderate rectangular orifice synthetic jets in a cross-flow. However, the bifurcation of a vortex ring while interacting with a cross-flow boundary layer develops differently than a natural bifurcation due only to self-induced vortex deformations.…”

Quantification of the S817 airfoil aerodynamic properties and their control using synthetic jet actuators

“…The injection of momentum and vorticity into the flow results in a delay of flow separation . A further description of the mechanisms by which synthetic jets add momentum and vorticity into the flow is detailed in Glezer and Amitay and Van Buren et al . Generally, the strength of an array of synthetic jets is described by the momentum coefficient C μ , which is the ratio of momentum injected during the outsroke of the synthetic jet to the momentum of flow over the airfoil, given by where n is the number of synthetic jets and is the time averaged synthetic jet momentum during outsroke and can be written as …”