Numerical simulation and dynamic mode decomposition analysis of the flow past wings with spanwise waviness

Abstract

This paper presents an investigation on the compressible flow past spanwise wavy wings with an incoming flow of [Formula: see text] and [Formula: see text]. The scale adaptive simulation is employed here to solve the Favre-averaged equations. Three wings, with the ratio of wavelengths (λ) to chord length (c) respectively equaling to 1/2 (W4), 1/3 (W6), 1/4 (W8), are aerodynamically investigated. The aerodynamic force and separation were compared. The results obtained show that the lift-to-drag ratio of W-8 is 12.7% and 14.4% higher than W-4 and W-6 because of the larger low-pressure regions, while the lift and drag coefficient curves of W-8 oscillate more strongly. Leading edge separated bubbles and dilation-type recirculation regions are observed in the flow field structures. Spanwise momentum transportation and local airflow downwash effect are generated by the flow around the separation regions. Spanwise momentum transportation and downwash effect play important roles in the flow control mechanism of spanwise wavy wings. Three components of three-dimensional velocity vectors are modally decomposed by dynamic mode decomposition method to reveal the flow control mechanisms and vortex structures. The main modes characterizing the motions of arched vortices and shear layer vortices have been obtained. Strouhal number (St) is adopted to define the periodic oscillations of vortex shedding. The St of the modes are related to the scale of the vortex structures in the flow field. Small-scale eddy motions have been decomposed in high-frequency modes, and thus the modes of the flow field are more meticulous for higher St.

Keywords

• Turbulence
• spanwise wavy wing
• numerical simulation
• flow control
• dynamic mode decomposition