Abstract
Over the last decade, aircraft morphing technology has drawn a lot of attention in the aerospace community, because it is likely to improve the aerodynamic performance and the versatility of aircraft at different flight regimes. With the fast paced advancements in this field, a parallel stream of research is studying different materials and designs to develop reliable morphing skins. A promising candidate for a viable morphing skin is the sliding skin, where two or more rigid surfaces remain in contact and slide against each other during morphing. The overlapping between each two panels create a backward-facing step on the airfoil surface which has a critical effect on the aerodynamics of the wing. This paper presents a numerical study of the effect of employing a backward-facing step on the suction side of a National Advisory Committee for Aeronautics (NACA) 2412 airfoil at a high Reynolds number of 5.9 × 106. The effects of the step location on the lift coefficient, drag coefficient and critical angle of attack are studied to find a favorable location for the step along the chord-wise direction. Results showed that employing a step on the suction side of the NACA 2412 airfoil can adversely affect the aforementioned aerodynamic properties. A drop of 21.1% in value of the lift coefficient and an increase of 120.8% in the drag coefficient were observed in case of a step located at 25% of the chord length. However, these effects are mitigated by shifting the step location towards the trailing edge. Introducing a step on the airfoil caused the airfoil’s thickness to change, which in turn has affected the transition point of the viscous boundary layer from laminar to turbulent. The location of the step, prior or post the transition point, has a noteworthy effect on the pressure and shear stress distribution, and consequently on the values of the lift and drag coefficients.
Highlights
This study focuses on the aerodynamics perspective of the employed backward-facing step sliding morphing skins
The study and analysis of the numerical results showed that a price has to be paid when using sliding morphing skin with a backward-facing step on the suction side of the airfoil
In comparison with the unchanged airfoil profile, employing a step on the suction side of the National Advisory Committee for Aeronautics (NACA) 2412 airfoil had with the unchanged airfoil profile, employing a step on the suction side of the NACA 2412 airfoil an adverse effect on the lift coefficient ccll, the drag coefficient ccdd and the critical angle of attack ααcccc
Summary
Nature has always been a source of inspiration for many engineering applications, and Aerospace engineering in particular is one the fields that holds a considerable share from these biomimetic inspired designs. This study focuses on the aerodynamics perspective of the employed backward-facing step sliding morphing skins. Results showed improved stall characteristics at all at all tested airspeeds, increased lift coefficients and increased lift-to-drag ratios over a wide range of tested airspeeds, increased lift coefficients and increased lift-to-drag ratios over a wide range of angles angles of attacks This enhanced performance of airfoils with a backward facing step on the suction of attacks. This enhanced performance of airfoils with a backward facing step on the suction side was side was not in a perfect agreement with the results obtained by the numerical and experimental not in a perfect agreement with the results obtained by the numerical and experimental testing done by Finaish and Witherspoon [16] In their study, they followed a more systematic way to examine. The effect of varying the step location will be thoroughly studied on the three aforementioned aerodynamic properties
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