Flow Control of a Sharp-Edged Airfoil

Effect of Airfoil Shape on Flow Control by Small-Amplitude Oscillations

“…There is a large region of separation over the suction surface of the airfoil. The airfoil can therefore be classified as fully stalled in agreement with the force measurements already presented, and by other authors [21,22]. The flat plate experiences a similar region of separation, although due to the smaller radius of curvature at the leading-edge the point of separation is closer to the leading-edge.…”

Experimental closed-loop control of separated-flow over a plain flap using extremum seeking

“…This is the case in the work of Miranda et al (2005) who use an oscillating flap and find that the optimal forcing frequency for a sharp-edged airfoil is, as in the previous studies, equal to the frequency of the vortex shedding which is naturally developed in the uncontrolled post-stall flow. Miranda et al (2005) also show that the same conclusion can be drawn from the early studies of Seifert and Pack (1999) and Roos and Kegelman (1986) provided that a proper calculation of the Strouhal number is proceeded. Audier et al (2012) exhibit a significant lift increase on a NACA 0012 profile when the forcing frequency applied through a surface DBD actuator is equal to the vortex shedding one.…”

“…According to the previous studies, the sensitivity outbreak is linked to the natural development of vortex shedding, so the lower limit of sensitivity is linked to the stall angle of attack. Besides, this lower limit should depend on the control amplitude since it is always possible to fully reattach the post-stall flow provided that enough momentum is injected, as recalled by Miranda et al (2005). They also find an upper limit beyond which the post-stall flow is no more sensitive to forcing frequency.…”

Fluid–structural dynamic characterization of an electroactive membrane wing

“…It has been speculated by other work that the shedding frequency will lock on to the natural resonant frequency of the membrane (Miranda et al, 2005;Rojratsirikul et al, 2010;Scott et al, 2012;Timpe et al, 2013). This is due to the larger density of the structure relative to the surrounding fluid behaving as a moving wall.…”