Four different circulation controlled airfoils have been numerically simulated. The baseline airfoil was a 17% thick supercritical airfoil. Different blowing rates have been examined by adjusting the slot height and blowing velocity. A number of turbulence models were employed, these were: Spalart-Allmaras, standard–", realizable–", SST–! and Reynolds stress model. The results from the numerical simulations were compared with experimental data at zero angle of attack. The solutions indicated that at momentum coefficients, C ¼ 0: 1 or greater, all isotropic turbulence models failed to capture the physics of the circulation control problem. The Reynolds stress model captured successfully the physics at C ¼ 0: 1. At greater values of momentum coefficient, the Reynolds stress model also failed to predict the experimentally measured lift coefficients because the jet remained attached to the surface of the airfoil. The Spalart-Allmaras model consistently predicted the right trend for lift variation with C in all cases tested.