Investigation on Length Effect of Seals between Inboard Flap and Outboard Flap of a Civil Aircraft

Seals are usually designed and installed in high lift devices of a civil craft for maintaining good aerodynamic performance and improving the issues such as aerodynamic noise and flap vibration. This paper addresses an investigation on the seals between inboard flap and outboard flap and analyze the length effect of seals on separation flow. The Computational Fluid Dynamics (CFD) simulations are performed with solving three-dimensional incompressible Reynolds-averaged NavierStokes (RANS) equations, and the turbulence is simulated with the k-omega shear stress transport (SST) turbulence model. According to the comparisons of four configurations of seals with different lengths, the existence of seals only has an effect on the nearby region, thus having no significant effect on lift and drag coefficients of the whole aircraft. When the seals did not make the opening space between inboard flap and outboard flap totally sealed, the flow on pressure surface moves upwards through the space and breaks the separation vortex around the seals, thus weakening the separation flow. Furthermore, with the length of seals getting shorter, the disturbed region on suction surface of flaps becomes larger, the region of separation flow becomes smaller consequently. An appropriate length of seals between inboard flap and outboard flap can not only ensure lift requirements, but also help prevent the issues such as flap vibration from happening by weakening the separation flow. The results and analysis will provide a guidance reference in aerodynamic design of seals between inboard flap and outboard flap.