Numerical Investigation of Boundary Layer Control Over an Airfoil

Abstract

Fluid flow over a blunt body causes a phenomenon called a boundary layer to occur. The viscosity of the fluid and the force caused by it between fluid layers are responsible for developing the boundary layer. Boundary Layer Separation occurs due to adverse pressure gradient which combined with the viscous forces on the surface, produces flow reversal, thus causing the stream to detach itself from the surface. This paper is focused on numerical investigation of flow separation and its control over a NACA4412 Airfoil, NACA2415 Airfoil & Joukowski Airfoil. The numerical simulation was carried out by commercially available software FLUENT 6.2 which solves the two-dimensional Navier–Stokes equations for compressible flow using a fully implicit method. In this study we employed structured grid for meshing. Viscosity model k-ε and Spalart-Allmaras were used. The numerical study was carried out using no slip boundary condition at Airfoil body for four different angles of attack 20, 40, 80 and 100 and with Mach number of 0.4066 as well as 0.60. To study boundary layer separation control, Active Flow Control method (Suction & Blowing) was employed and numerical study was repeated with suction & blowing boundary condition at Airfoil body for above mentioned angle of attack and Mach number. The simulation results were compared with experimental results of Kjetil Birkeland Moe project report 2008 and found in good agreement. From the FLUENT runs, the k-ε model had the overall best performance in determining the lift and drag coefficients and optimum airfoil angle of attack in terms of lift and drag coefficient found to be at 8°.The effect of suction on aerodynamic coefficients was investigated. The results showed that the surface suction with velocity 0.5 m/sec can significantly increase the lift coefficient up to 6.89% and drag coefficient reduces up to 11.76%, delay the separation & decreases the skin friction.