Effect of Flexibility on Aircraft Wing

Abstract

The shape of the aerofoil determines how the air circulates around it and how much moment and force will be the acting on it. When the body is rigid (fixed) flow around the geometry remains unchanged at particular A.O.A. (angle of attack), but if the body is allowed to be flexible (free) i.e., it can deform its shape, due to which there will be a significant change in the shape of geometry that consequently changes the motion of air flow around it altering the moment and forces generated. This will led to a change in the distribution of pressure on the flexible membrane causing the A.O.A. to vary, due to which wing’s geometrical shape try to adopt it accordingly by forming a luff. This luff is mostly formed from the leading edge i.e., due to the membrane’s elastic nature; in the flow to adjust change prevailed. A computational approach was made to understand this effect. This was the main purpose of the project to be carried out. The dissertation mainly focuses onto understand the effect of flexibility on aerodynamics and performance of wing compared to the normal rigid wing section using the most simplified case for long term goal of finding out the behavior of aerodynamics on wings of pterosaur with and without fairing (soft membrane). The study was carried out by taking into account a specific case of pterosaur’s gliding flight at a speed of 33.3 m/s. This project included two test cases firstly, the rigid wing and secondly the flexible membrane wing, which were tested for both steady and unsteady viscous incompressible flows. For both the test cases it was considered that tension is mainly dominated by elastic strain (∏₁). Both the test cases were carried out at fixed Reynolds’s number of 1.087 ´ 10⁵ and Mach number 0.098. Use of equation similar to the bending of beam equation which is often referred as “Young Laplace Equation” was incorporated, that was modeled to a discrete formulation using second order accurate finite difference scheme. When the membrane of the wing was considered flexible there was a significant effect on forces generated, which in turn had an effect on performance in terms of coefficient of lift. Finally, comparisons between performances based on coefficient of lift of both test cases were carried out. The results obtained shows that the coefficient of lift for flexible case increased by 40% when compared to the rigid wing.

 Keywords: Young Laplace Equation, flexible wing, pterosaur wing, wing concept, morphing

Cite this Article

Milan Patel, Nikunj Mashru. Effect of Flexibility on Aircraft Wing. Journal of Aerospace Engineering and Technology. 2016; 6(1): 45–50p.