Theoretical Analysis of Perching and Hovering Maneuvers

On the leading-edge suction and stagnation-point location in unsteady flows past thin aerofoils

“…This expression is seen to have a similar form to that derived for steady flow (van Dyke 1956), with A 0 replacing a parameter that is related to the steady angle of attack. This is consistent with the fact that in previous research (Ramesh et al 2013(Ramesh et al , 2014, the A 0 term in unsteady thin-aerofoil theory has been shown to be an "effective unsteady angle of attack" consisting of contributions from the geometric angle of attack, aerofoil camber, plunge velocity and induced velocities by the wake.…”

“…Detailed description of this approach and its implementation may be found in Ramesh et al (2013) and Ramesh et al (2014). For further discussion in this article, we assume that the aerofoil travels at a constant horizontal velocity and that there are no external disturbances.…”

“…Originally developed for steady flows about an aerofoil at a constant angle of attack, thin-aerofoil theory has also been extended to unsteady flows (Katz & Plotkin 2000). Ramesh et al (2013) have derived such a theory valid for arbitrarily large amplitudes and non-planar wakes. Though the need to model free vorticity interaction in the wake makes this method semi-numerical in comparison with completely closed-form theory like Theodorsen (1935), it is applicable to a wider range of scenarios occurring in nature and engineering.…”

“…This method has been used in studies on diverse topics including design of efficient flapping aerofoils through morphing (Willis & Persson 2014), and power generation by self-sustained oscillation of an aeroelastic aerofoil (Ramesh et al 2015). The "A 0 " term in this method is of particular interest and has been used to develop a new aerodynamic entity called the Leading-Edge Suction Parameter (LESP) in Ramesh et al (2014). It has been shown through experimental and numerical verification that the process of leading-edge vortex (LEV) formation is strongly correlated to the local suction at the leading edge and hence the LESP (Ramesh et al 2018;Deparday & Mulleners 2018.…”

“…The "A 0 " term in this method is of particular interest and has been used to develop a new aerodynamic entity called the Leading-Edge Suction Parameter (LESP) in Ramesh et al (2014). It has been shown through experimental and numerical verification that the process of leading-edge vortex (LEV) formation is strongly correlated to the local suction at the leading edge and hence the LESP (Ramesh et al 2018;Deparday & Mulleners 2018. This parameter has been used to predict and control the occurrence of LEV formation, and in discrete-vortex methods for modelling intermittent LEV shedding on aerofoils/wings where the LESP is used to both predict LEV formation and modulate the strength of discrete vortices shed from the leading edge (Ramesh et al 2014(Ramesh et al , 2017Hirato et al 2019).…”