The mechanisms of drag reduction through bionic microstructures on fan blade surfaces

This article proposes a passive flow control method for arranging bionic microstructures on the surface of fan blade based on the structural characteristics of shark shield scales. The mechanisms of drag reduction through bionic microstructure were analyzed by numerical simulation at a Mach number of 0.5 and angles of attack from −6° to 9°. The bionic microstructure effectively increases the binding ability of wall to the fluid and the viscous force. This resulted in a decrease in the velocity gradient within the boundary layer and an increase in the viscous sublayer's thickness, so the wall shear stress on the suction surface was diminished and the position of the separation point on the blade surface was delayed by 7.7% of the axial chord length in comparison with that of the smooth blades. The turbulent intensity in the fluid domain on the suction side was reduced by 17.2% within the cascade passage. The total pressure loss coefficients were decreased, respectively, by 14.3%, 17.9%, and 29.1% at angles of attack of 0°, 6°, and −9° compared to the smooth blades. The frictional drag was reduced by the bionic microstructure effectively, thereby enhancing the pressure expansion capability of the cascade. The static pressure coefficient was increased by 5.4% at the angle of attack of 0° and the angle of attack corresponding to the peak point varies from 3° to 6°. The cascade has a wider application range for the angle of attack.