The physics of a perturbed flow around the wind power plant turbine is rather complex. When passing through the plane of rotation, the airflow gets substantially perturbed. In such conditions, the pressure of ram air changes stepwise when passing through the plane of the wind turbine rotation, which is related to the loss of flow mechanical energy and its transfer to the rotor. A complex vortex system is created behind the turbine. In this system, it is possible to single out at least three distinctive groups of vortices: attached vortices on blades, a free helicoidal vortex that forms when the flow is passing through the blade ends, and an axial vortex forming at the expense of flow swirling on the wind turbine. In a real flow, the whole perturbed area is filled with vortices, which makes it quite difficult to perform a physical analysis and mathematical calculation of the flow. The article presents the results of calculating and simulating the aerodynamic characteristics of a propeller-type wind turbine with a horizontal axis of rotation. The calculations are based on the theory of elementary streams, which is a compilation of the results of the momentum theory of the ideal wind turbine and a wing theory, which is quite well developed now. On this basis, it is possible to substantially expand the study and description of physical processes related to wind turbine flow. The rated power of the wind power plant, rated wind speed, wind speed at gusts, number of blades, etc. were taken as initial data. For the selected wind turbine blade airfoil of “Espero” type an angle of attack, a lift coefficient and a drag-to-lift ratio were determined. During the calculation and simulation the cases of an airfoil with and without a geometric twist were considered. As a result of the calculation and computer simulation, there were determined the optimal values of the coefficients of: flow deceleration, ideal power, end and profile losses, blade tip specific speed.