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A computational model of a wind tunnel (WT) with a special experimental rig has been developed directly for studying unsteady aerodynamic characteristics of a wing section with a helicopter blade profile. The model was constructed using CFD (Computational Fluid Dynamics) methods based on the URANS approach (Unsteady Reynolds Averaged Navier Strokes Equations). Therefore, the aerodynamic characteristics of the airfoil can be determined, taking into account influence of the WT walls such as walls perforation and various configurations of the experimental rig. Simulation of the flow around the wing section with the SC1095 airfoil in steady and unsteady settings is performed. The flow features in the working section of the WT and the experimental rig are analyzed. For a particular case, the calculation method was validated in a 2D formulation on the basis of available experimental data. The developed model can be used to refine the methods of processing experimental data, taking into account the individual characteristics of the WT and the experimental rig configuration.

The presented work is dedicated to the numerical study of the aerodynamic characteristics of the helicopter rotor. Two approaches to modeling of the rotor are applied: the free wake model developed by the Authors with using steady airfoil characteristics and the Unsteady RANS method based on the Ansys Fluent software. The modes of hovering and horizontal flight in the range of advancing ratio μ = (0-0.45) are considered. The shapes of the rotor wake, the distributions of the normal force coefficient and the fields of inductive velocities for all considered flight modes are calculated. For a particular case with μ = 0.25 there is a comparison with experimental data. The time needed for calculation of the applied methods is estimated. Accuracy of the used methods in the framework of the solved task is analysed with taking into account used models assumptions. It is shown that in the range of μ = (0-0.25) the free wake model provides a fast and reliable calculation of the aerodynamic characteristics of the helicopter rotor. For values of μ > 0.35 it is necessary to take into account the unsteady characteristics of the airfoil.

This paper considers the Mi-8 helicopter main rotor aerodynamics when flying near the infinite ground surface. The research is based on the free wake model developed by authors at Moscow Aviation Institute. The distance from the rotor's hub to the ground surface in the range of H = 6−16 m and the values of free stream (flight) velocity in the range of V = 0−15 m/s are considered. The results of the visualization for both rotor wake shapes and streamlines are obtained. The influence of the ground proximity on the rotor wake shape, including the formation of "supervortex" and "ground vortex" structures are analyzed. The induced velocity fields of the main rotor in the area of the tail rotor location for various azimuth positions relative to the main rotor axis are studied. The conclusion is made about the significant influence of the ground effect on the rotor wake structure and induced velocities field, including the area of the tail rotor location. Particularly, at slip flight with speed V = 10 m/s, when the distance to the ground surface H increases from 6 to 12 m, the value of the average induced velocity at the tail rotor plane is growing up to four times. The obtained data have allowed taking into account such effects of aerodynamic interference in the simplified mathematical model of the research flight simulator of JSC Helicopters Mil and Kamov.