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Updated: Aug 5, 2026

Cryogenic Liquid Jets for High Repetition Rate Discovery Science
Published on: May 9, 2020
Actuation parameters and boundary layer height effects on a circular synthetic jet in crossflow
Howard Haonan Ho1, Ebenezer Ekow Essel2, Pierre Edward Sullivan1
1Department of Mechanical and Industrial Engineering, University of Toronto, Toronto, Canada.
Abstract:
Three-dimensional unsteady numerical simulations are performed to investigate the effects of blowing ratio [Formula: see text] ([Formula: see text]), stroke ratio [Formula: see text] ([Formula: see text]), and boundary-layer height ratio [Formula: see text] (2.1<δ /d<8.0) on circular synthetic jet actuator (SJA) performance in crossflow. Nine cases are examined at constant free-stream velocity [Formula: see text], with systematic independent variation of averaged jet velocity [Formula: see text], actuation frequency f (200-[Formula: see text]), and boundary-layer momentum thickness Reynolds number ([Formula: see text]) to examine the influence of these parameters across varying boundary-layer conditions on a circular-nozzle SJA with fixed nozzle diameter d in crossflow. Instantaneous vortical structures exhibited tilted vortex rings with a trailing vortex pair at low actuation frequency; closely packed expelled vortical structures for higher frequency SJAs, and the largest boundary-layer height ratio induced hairpin-like vortices. Near-wall tertiary vortices, which promote downwash and increase wall shear stress, remain coherent longer and have extended spanwise coverage for low [Formula: see text]. Time-averaged boundary-layer profiles and skin-friction distributions reveal that SJAs with low to moderate [Formula: see text] have the greatest potential for separation control, maintaining increased near-wall momentum over extended streamwise distances.
Supplementary Information:
The online version contains supplementary material available at 10.1007/s44369-026-00011-9.
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