Flow separation control using a bio-inspired nose for NACA 4 and 6 series airfoils

Abstract

Purpose This paper aims to achieve an optimum flow separation control over the airfoil using a passive flow control method by introducing a bio-inspired nose near the leading edge of the National Advisory Committee for Aeronautics (NACA) 4 and 6 series airfoil. In addition, to find the optimised leading edge nose design for NACA 4 and 6 series airfoils for flow separation control. Design/methodology/approach Different bio-inspired noses that are inspired by the cetacean species have been analysed for different NACA 4 and 6 series airfoils. Bio-inspired nose with different nose length, nose depth and nose circle diameter have been analysed on airfoils with different thicknesses, camber and camber locations to understand the aerodynamic flow properties such as vortex formation, flow separation, aerodynamic efficiency and moment. Findings The porpoise nose design that has a leading edge with depth = 2.25% of chord, length = 0.75% of chord and nose diameter = 2% of chord, delays the flow separation and improves the aerodynamic efficiency. Average increments of 5.5% to 6° in the lift values and decrements in parasitic drag (without affecting the pitching moment) for all the NACA 4 and 6 series airfoils were observed irrespective of airfoil geometry such as different thicknesses, camber and camber location. Research limitations/implications The two-dimensional computational analysis is done for different NACA 4 and 6 series airfoils at low subsonic speed. Practical implications This design improves aerodynamic performance and increases the structural strength of the aircraft wing compared to other conventional high lift devices and flow control devices. This universal leading edge flow control device can be adapted to aircraft wings incorporated with any NACA 4 and 6 series airfoil. Social implications The results would be of significant interest in the fields of aircraft design and wind turbine design, lowering the cost of energy and air travel for social benefits. Originality/value Different bio-inspired nose designs that are inspired by the cetacean species have been analysed for NACA 4 and 6 series airfoils and universal optimum nose design (porpoise airfoil) is found for NACA 4 and 6 series airfoils.

Bio-inspired optimization of leading edge slat

“…Hence, it can be used in medium-speed transport aircrafts to increase the C l and the aerodynamic efficiency than the conventional high lift devices such as flap, slat, etc. (Raj Mohamed and Yadav, 2021) From the review, it has been inferred that the high lift devices are effective at high angle of attack to increase the coefficient of lift by increasing the camber. But they affect the low angle of attack aerodynamic performance by increasing the drag.…”

“…The bio-inspired nose designs, which are inspired by the cetacean species nose designs, were analyzed for the subsonic speed and found that the Dall’s Porpoise nose showed the better aerodynamic efficiency at all angles of attack with increase in C l (Raj Mohamed et al , 2019). The optimum bio-inspired (porpoise) nose enhances the aerodynamic efficiency for different NACA 4 and 6 series airfoils; hence, it can be made as a simple and fixed LE device which can be installed easily on the existing aircrafts (Raj Mohamed et al , 2021). The porpoise nose works well up to the critical Mach number and failed after that because of the shock wave formation.…”