Near-Wake of a Circular Cylinder: Control, By Steady and Unsteady Surface Injection

Aerodynamic drag reduction of a simplified squareback vehicle using steady blowing

“…Previous authors (Lin 1999) have placed an emphasis on the requirement for high C µ . In the current work higher C µ values could be achieved using lower freestream velocities, however freestream velocities were only reduced within a region where results were found to be insensitive to Reynolds number.…”

“…In fundamental studies of active flow control techniques the techniques are generally implemented at, or near, points of separation in order that the formation of the wake may be controlled (Lin 1999;Brunn 2006). Generally in 2D bluff body applications periodic structures that are normally shed into the body wake are targeted by the control technique in the hope that wake size can be modified.…”

Modification of the wake behind a circular cylinder by using synthetic jets

“…These types of unsteady pneumatic actuators have the characteristics of being possibly miniaturized, they do not produce any average mass addition to the near wake and they require very little energy. Lin et al (1995) have used simultaneous applications of steady blowing and unsteady blowing-suction (through a helical pattern of small holes about the surface of a cylinder) and prescribed oscillations of the model in the cross stream direction, which produced a dramatic effect on the near-wake structure. The characteristics of unsteady actuators are of great interest and explain that the pulsed jets and synthetic jets have also been tested with success on various types of other models.…”

Features of flow past a circular cylinder with a slit

“…Intermediate spacing leads to very complex transitional patterns, like bi-stable biased gap ow observed by Kim and Durbin [39]. Also, relevant investigations on the ow control include suction or blowing on a blu body, such as Wood [40], Lin et al [41], and Kim and Choi [42]. A recent study of Baek and Karniadakis [43] investigated numerically the Vortex-Induced Vibrations (VIV) control via a slit, and they observed that a slit parallel to the ow direction could both weaken and detune the vortex shedding, which is e ective in suppressing the VIV.…”