Numerical Investigation of Boundary Layer Separation Control Over an Airfoil

Abstract

Fluid ow over a blunt body causes a phenomenon called a boundary layer to occur.The viscosity of the uid and the force caused by it between uid layers are respon-sible for developing the boundary layer. Boundary Layer Separation occurs due toadverse pressure gradient which combined with the viscous forces on the surface, pro-duces ow reversal, thus causing the stream to detach itself from the surface. Thispaper is focused on numerical investigation of ow separation and its control over aNACA4412 Airfoil, NACA2415 Airfoil and Joukowski Airfoil. The numerical simula-tion was carried out by commercially available software FLUENT 6.2 which solves thetwo-dimensional Navier-Stokes equations for compressible ow using a fully implicitmethod. In this study we employed structured grid for meshing. Viscosity modelk-" and Spalart-Allmaras were used. The numerical study was carried out using noslip boundary condition at Airfoil body for four dierent angles of attack 2o, 4o, 8oand 10o and with Mach number of 0.4066 as well as 0.60. To study boundary layerseparation control, Active Flow Control method (Suction and Blowing) was employedand numerical study was repeated with suction and blowing boundary condition atAirfoil body for above mentioned angle of attack and Mach number. The simulationresults were compared with experimental results of Kjetil Birkeland Moe project re-port 2008 and found in good agreement. From the FLUENT runs, the k-" modelhad the overall best performance in determining the lift and drag coecients andoptimum airfoil angle of attack in terms of lift and drag coecient found to be at8. The eect of suction on aerodynamic coecients was investigated. The resultsshowed that the surface suction with velocity 0.5 m/sec can signicantly increasethe lift coecient up to 6.89% and drag coecient reduces up to 11.76%, delay theseparation and decreases the skin friction.