Theoretical investigation of the aerodynamics of double membrane sailwing airfoil sections

The sailwing has many special characteristics due to its flexible structure. In order to estimate the sailwing performance theoretically, a numerical analysis method is presented for obtaining aerodynamic characteristics and profile forms of a sailwing with a rounded leading edge and upper and lower individual surface shapes. The trailing edge is fixed and membranes are not stretched by tension although they have slackness. Through numerical examples, it is shown that a sailwing of this type has a completely different pressure distribution from that of a single membrane sailwing with a leading edge of the circular cylinder or oval type. The latter has shape peaks in the pressure distribution which may have undesirable effects on the sailwing performance. These peaks in the pressure distribution can be removed by adopting a D-spar leading edge of some kind.