<p>With the use of multiblock computational technologies and the shear stress transport model modified with regard for the curvature of streamlines, calculations of the nonstationary turbulent flow of an incompressible fluid around a semicircular airflow, on the contour of which one or two circular vortex cells with slot suction are placed, at a zero angle of attack have been performed. On the basis of the calculation data obtained, regimes of stabilizing the flow around such an airfoil, close to the flow without separation, and the possibility of achievement of the extremal lift coefficient C_y = 5.8 by it at a lift-drag ratio K = 10, determined with account of the energy expended for the suction in the vortex cells, have been revealed. It was established that when the Mach number of the undisturbed flow around a semicircular airflow with two vortex cells increases to the critical value, C_y and K of the airfoil increase. In this case, C_ymax and K_max are of the order of 6.2 and 14.5, respectively. In the case of flow around this airfoil at a Mach number larger than M_cr, the second vortex cell does not function, and the flow around the airfoil becomes detached.</p>