Numerical Study of Coaxial Main Rotor Aerodynamics in Steep Descent

Abstract

Numerical studies of the aerodynamic characteristics of the coaxial main rotor of the Kamov Ka-32 helicopter in steep descent modes, including the area of the vortex ring state (VRS) modes, have been performed. Used in this paper is an original free vortex wake model of the rotor developed by the authors. The angles of attack of the rotor αR = 30 – 90° and the rate of descent in the range of Vy = 0–30 m/s are considered. The calculations have been carried out under the condition of a fixed time-average thrust of the rotor. The visualization of the rotor wake shapes the flow structures using streamlines, and the flow velocities have been received and analyzed. The VRS boundaries in “Vx–Vy” coordinates have been constructed. The criteria used in this paper are: rotor thrust and torque pulsations, rise of rotor torque and induced velocity relative to the hovering mode. The results of the calculations are compared with the experimental and calculated data of other authors, and a satisfactory match has been obtained. The new results presented in this paper can supplement the existing experience of experimental and numerical research in this field.

Numerical Investigation of the Vortex Ring Phenomena in Rotorcraft

“…The conditions for VRS formation typically involve a steeper descent with reduced engine power, relatively low horizontal speed V h , and a reasonably significant vertical descent rate V z [3,4]. In a favorable situation, with sufficient space, altitude, theoretical knowledge, and practical skills, corrective maneuvers can allow the helicopter to exit the Vortex Ring State and continue routine flight without any residual consequences [4][5][6][7]. However, problems arise when the distance to the ground or obstacles become dangerously short during such a steep descent with low horizontal speed.…”

“…Aerospace 2024, 11, x FOR PEER REVIEW 2 of 11 to exit the Vortex Ring State and continue routine flight without any residual consequences [4][5][6][7]. However, problems arise when the distance to the ground or obstacles become dangerously short during such a steep descent with low horizontal speed.…”